Alfred J. Freddoso
University of Notre Dame


My topic is God's activity in the ordinary course of nature. The precise mode of this activity has been the subject of prolonged debates within every major theistic intellectual tradition, though it is within the Catholic tradition that the discussion has been carried on with the most philosophical sophistication. The problem, in its simplest form, is this: Given the fundamental theistic tenet that God is the provident Lord of nature, the First Efficient Cause who creates the universe, sustains it in being, and exists in all things by His essence, presence, and power,1 how exactly do the actions of secondary (i.e., created) causes fit in with God's own activity in the ordinary course of nature? Or, to put it a bit more neutrally, how exactly is God's own action as the First Cause in nature related to the causal activity, if any, of His creatures?

Historically, this general problem of divine action in nature--or, alternatively, the problem of secondary causality in nature--emerged from reflection upon narrower but more immediately pressing problems. Within medieval Islamic philosophy, the rising influence of neo-Platonic necessitarianism, with its ostensible denial of the possibility of miraculous divine action, prompted orthodox thinkers to formulate metaphysical accounts of God's constant activity in nature as a backdrop against which the possibility of miracles might be persuasively defended. Within medieval Christian scholasticism, on the other hand, it was chiefly puzzlement over God's causal contribution to sinful human /132/ actions that led eventually to independent treatments of divine action in nature. The word 'eventually' must be emphasized here, however. For even though, in their discussions of sin, the so-called 'old' scholastics had come close to broaching the broader question of how God acts in the operations of secondary causes in general, St. Thomas himself was "the first scholastic doctor to treat this question in a special place, i.e., detached from the problem of the cause of sin, and to extend it explicitly to all natural operations, whether they be operations of nature or of the will."2

It is easy enough to imagine how St. Thomas's Aristotelianism might have led him to this innovation. First of all, from an Aristotelian perspective sinful actions are but one species of defects, i.e., actions or effects that in some aspect or other fall short of what they ought to be, given the natures of the relevant agents and patients. Consequently, a Christian Aristotelian will quite naturally view the problem of God's causal contribution to sinful actions as a proper part of the more extensive problem of God's causal contribution to defective actions and effects in general, including defects in nature. But a systematic treatment of this latter problem finds its proper home within a comprehensive account of God's action in the ordinary course of nature. Second, and even more basically, Aristotelians see free human action not as something entirely sui generis but instead as falling under a general definition of action that applies to non-rational as well as rational substances.3 Consequently, Christian Aristotelians will instinctively tend to approach the question of God's causal contribution to free human action, whether sinful or not, by first inquiring more generally about divine causality in the operations of non-rational creatures and by then gradually working their way up to an account of God's causal contribution to the free actions of rational creatures.

So much for the origins of the debate. I will now provide an informal summary of what have emerged historically as the three principal theistic accounts of God's causal influence in the ordinary course of nature:

Occasionalism. According to occasionalism, which was embraced by several important medieval and early modern thinkers, God alone brings about effects in nature; natural substances, contrary to common /133/ opinion, make no genuine causal contribution at all to any such effect. So, for instance, the water that soaked the ground during yesterday's downpour does not in any way causally contribute to the growth of the young pine tree in your front yard; rather, it is God alone who gives the tree growth on the occasion of the water's presence within it. The water is merely an occasional or sine qua non cause. That is, it counts as a 'cause' only in the attenuated sense that God acts in accord with a firm, though arbitrary, intention to give growth to pine trees on the occasion of their being spatially related to water in the right sort of way under the right sort of circumstances; and so it is, mutatis mutandis, for all the effects produced in nature.4 In short, God alone is a genuine efficient cause of natural effects.

Interestingly, despite its apparent outlandishness, occasionalism is a live option today for Christian philosophers, especially for those operating within mainstream Anglo-American philosophy. For it coheres quite nicely with the metaphysical anti-realism that marks some of the most influential contemporary treatments of causality and scientific explanation.5

Mere Conservationism. According to mere conservationism, God contributes to the ordinary course of nature solely by creating and conserving natural substances along with their active and passive causal powers or capacities. For their own part, created substances are genuine agents that can and do causally contribute to natural effects by themselves, given only that God preserves them and their powers in existence. When such substances directly produce an effect via transeunt action (i.e., action that has an effect outside the agent itself), they alone are the immediate causes of that effect, whereas God is merely an indirect or remote cause of the effect by virtue of His conserving action. Consequently, the actions of created substances are their own actions /134/ and not God's actions, and their effects are their own immediate effects and not God's immediate effects.

In the writings of many contemporary Christian philosophers and theologians, the truth of mere conservationism seems to be taken for granted; and so it may surprise you to learn that almost all the important figures in the history of Christian philosophical theology have rejected this position as philosophically deficient and theologically suspect--and justifiably so, to my mind.6 Durandus, an early fourteenth-century Dominican theologian, is the only well-known medieval proponent of mere conservationism, or at least the only one cited by sixteenth- and seventeenth-century writers.7 More on Durandus in a moment.

Concurrentism. Concurrentism, which flourished among the late medieval Aristotelian scholastics and certain figures in the early modern period, occupies a middle ground between what its advocates perceive as the unseemly extremes of occasionalism and mere conservationism. According to concurrentism, a natural effect is produced immediately by both God and created substances, so that, contrary to occasionalism, secondary agents make a genuine causal contribution to the effect and in some sense determine its specific character by virtue of their own intrinsic properties, whereas, contrary to mere conservationism, they do so only if God cooperates with them contemporaneously as an immediate cause in a certain "general" way which goes beyond the conservation of the relevant agents, patients, and powers, and which renders the resulting effect the immediate effect of both God and the secondary causes. This cooperation with secondary causes is often called God's general concurrence or general concourse.8

At first glance concurrentism appears eminently sane from a theistic standpoint, since it allows for secondary causality in a robust sense /135/ while at the same time sustaining a strong interpretation of the theological tenet that God is intimately involved in the production of effects in nature. But lurking below the surface are some intricate philosophical problems concerning cooperative transeunt action in general and God's cooperative agency in particular. Notoriously, certain of these problems were resolved in radically different ways by the sixteenth-century Dominicans, led by Domingo Bañez, and their Jesuit counterparts, most notably Luis de Molina and Francisco Suarez.9 Here, however, I will set aside these differences and concentrate instead on the challenge presented to both parties by Durandus, who had argued almost three centuries earlier that the problems faced by concurrentism are in principle irresolvable. Durandus's two main objections to concurrentism are not to my mind successful or even, in the end, very impressive. Still, the discussions leading up to those objections highlight two potential pitfalls for the concurrentist, and a close examination of these pitfalls, which I undertake in sections 3 and 4, will serve to delineate more precisely the challenges that await any attempt to articulate and defend an adequate account of God's general concurrence within the arena of contemporary philosophical theology. I begin in section 2 by expounding certain basic, though somewhat technical, scholastic theses about the nature of transeunt action.10 This will provide us with an ontological framework within which we can situate what Durandus has to say.


The Aristotelian scholastics take efficient causality in the primary sense to consist in the direct production or conservation of an effect by /136/ an agent.11 In a typical case (excluding creation ex nihilo) one or more agents act upon a patient in such a way as to produce an effect, where the effect is itself either a substance or an accidental modification of a preexisting substance. More technically, a typical agent or efficient cause is a principle that directly (per se) communicates being (esse)--either substantial being or accidental being--by means of action on a patient. This is the core account, and on this basis one can go on to characterize the types of per se efficient causality (e.g., principal and instrumental, univocal and equivocal, transeunt and immanent), the distinction between efficient causality properly speaking and the prerequisite conditions for causal action, and the several types of per accidens causal relations (e.g., remote causality, corruptive causality, chance).

I will now expand a bit on the two principal elements in the core account, viz., the notion of esse and the notion of action.

According to St. Thomas, esse is a principle of actuality which in any given finite entity is proportioned to that entity's nature or essence.12 In the more Platonic idiom that St. Thomas also employs, a finite created entity is said to "participate in" or "have a part of" esse-as-such. This is because all created entities have some proper part of, or finite share in, the whole gamut of possible perfections; that is, they have esse as delimited by their natures to what in each particular case is the esse proper to the sort of entity in question. So, for instance, a white oak tree has the esse proper to a white oak tree and, subordinated to it, the esse proper to its various separable and inseparable accidents. The same holds for armadillos, rhododendrons, water molecules, hydrogen atoms, photons, etc. This explains the spirit behind St. Thomas's claim that for a living organism to exist is for it to be alive, i.e., to have esse or actuality as proportioned to a living organism.13 So when a typical efficient cause /137/ communicates esse through its action, it gives actuality or perfection of some sort or other--either by producing a substance of a given natural kind, or by producing some accidental form or determination in an already existing substance.14

Thus, the term 'to have esse', unlike the term 'to exist' in at least one common use, admits of different degrees or levels--where God, who is Subsistent or Unparticipated Esse, the Fullness of Being, constitutes the incommensurable upper limit. Still, the two terms are equivalent in the sense that a created entity exists if and only if it has esse as delimited by some nature or other.

More importantly in the present context, if, as Bañez points out, we consider the esse received in a given creature "just insofar as it bespeaks existence absolutely, i.e., not as contracted and determined to the specific or individual esse in which it is received and delimited ... [then esse so construed is] that through which creatures stand outside of nothingness."15 In technical terms, for an entity to have esse as delimited to a given nature is, in part, for it to have esse in general or esse commune, that in virtue of which it is something rather than (literally) nothing. Thus, the communication of esse in any given instance of efficient causality always involves two distinguishable aspects, viz., (a) the communication of that which makes the effect something rather than nothing, and (b) the communication of that which makes the effect to be of one particular kind rather than another. This duality will become important below.

I turn now to action. Notice, to begin with, that the determinate effects produced in given instances of efficient causality are a function of the causal powers or capacities belonging to the relevant agents and patients. A substance's active powers delimit the range of its 'proper' effects, i.e., the effects it is capable of producing directly by its own power /138/ when it acts upon suitably disposed patients in appropriate circumstances. Correlatively, a substance's passive powers delimit the range of effects that might be produced in it when it is acted upon by suitably situated agents in appropriate circumstances.

So we can view a typical transeunt action from two sides, that of the agent and that of the patient. From the side of the agent, the existence of an action requires the exercise, or fully actualized state, of a certain accident, viz., an active power, had by the agent; and it is due to this exercise of power that the effect is said to 'emanate' or 'flow' from the agent.

Two crucial points must be noted here. First of all, even though everyone acknowledges that the active power which is exercised is a real accident inhering in the agent, the general consensus is that the action itself--i.e., the very exercising of this power--is not an additional and distinct accident or reality inhering in the agent. To the contrary, the entity or reality signified by the term 'action' is a determination that (leaving aside creation) has the patient, rather than the agent, as its ultimate ontological subject. To be sure, this reality is called an action precisely because it emanates from the agent and constitutes (or, on some accounts, 'results in') the effect's causal dependence on the agent at the very time at which the agent is producing it. Moreover, it is precisely because of this contemporaneous dependence of the effect on the agent that the agent itself is truly said to be acting. However, when the term 'is acting' is predicated of the agent, we have a case of what the scholastics call extrinsic denomination, i.e., a predication which is such that its truth is grounded in the subject's relation to a reality extrinsic to itself.16 What's more, the effect determines the nature of the action in two important respects. First of all, sameness of effect is a necessary condition for sameness of action and, correlatively, distinctness of effect is a sufficient condition for distinctness of action; and, second, for every proper effect there must be an action that is proportioned to that effect and hence sufficient to produce it directly or per se. Both these points will become significant later on when we delve into the nature of cooperative action.17

These considerations help to explain and render at least plausible a common scholastic adage that non-scholastic philosophers often find initially puzzling, viz., that a created agent's transeunt action exists in the patient and thus has the patient, rather than the agent, as its /139/ ultimate ontological subject. For if an action essentially involves the production of an effect by an agent, then it follows straightaway that it is impossible for there to be an action unless an effect is produced.18 And the most natural explanation for this impossibility is just the scholastic thesis that an action, though emanating from the agent, is ontologically rooted in the effect and hence in the patient.

There is yet another way to see the warrant for the scholastic adage. Suppose that all the prerequisites for an agent's acting are satisfied in a given case. These include the agent's having a sufficient power to produce a given effect in a properly disposed patient, the agent's being appropriately situated with respect to the patient, the patient's being properly disposed to receive the formal determination that the agent is ready to communicate, the absence of impediments, etc. Then what is the difference between the agent's acting in such a case and its not acting? The common scholastic response is that the difference is just the coming to be of the relevant effect in the patient insofar as that effect is dependent on the agent. So no new entity need be added to the agent; instead, the action consists in something's being added to the patient. And, once again, this seems plausible. To paraphrase Suarez, an action is a path (via) leading from the agent, by virtue of the agent's active power, to its destination in the effect--and not something that inheres in the agent itself.

However, we must be very careful at this juncture--and here I introduce the second of the crucial points alluded to above. Although the scholastics use Latin terms like influxus, influentia, and emanatio to signify the agent's influence on the patient, they all deny that transeunt action involves the literal transfer of some entity--i.e., perfection or form--from the agent to the patient. Certain early occasionalists had assumed, to the contrary, that an Aristotelian account of efficient causality does indeed entail just such a transfer of forms, and they had argued from the absurdity of this consequent to the conclusion that there is no transeunt action in the material universe. St. Thomas replied as follows:

It is ridiculous to assert that the reason why bodies do not act is that no accident passes from one subject into another. For a hot body is said to produce heat not in the sense that numerically the same heat that exists in the heating body passes over into the heated body, but rather because by virtue of the heat that exists in the heating body a numerically distinct heat comes to exist in actuality in the heated body--a /140/ heat that beforehand existed in it potentially. For a natural agent does not transfer its own form into another subject, but instead reduces the subject that is acted upon from potentiality to actuality (Summa Contra Gentiles 3, chap. 69).

Some early modern philosophers, most notably Leibniz, complained of the obscurity of this metaphysical model, with its invocation of the 'reduction' to actuality of the patient's potentiality.19 If the agent transfers nothing of itself to the patient, then, they asked, how exactly does the Aristotelian picture of a material agent's educing an effect from a patient's potentiality differ from the occasionalist picture, according to which the presence of the material substance merely provides an occasion for the effect's coming to exist in the patient? In other words, if there is no transfer of forms, then what precisely does an effect's causal dependence on a material agent add, ontologically speaking, to the putative agent's merely being present in the right sort of way when the effect comes into existence? How, precisely, can one paint an intuitively satisfying picture of the communication of esse to the patient by the agent without appealing to the transfer of some reality in the agent to the patient?

To begin with, notice that those who, like Malebranche and Berkeley and Leibniz, acknowledge the reality of divine transeunt action even while denying transeunt agency to natural bodies must answer a question similar to the one that they pose for Aristotelians: 'What does God's transeunt action consist in?' Obviously not in the literal transfer of any entity from God to a creature. Well, then, what does it consist in? The most straightforward answer is that it is simply the agent's causal influence as terminated in the effect--which is exactly what the Aristotelians say in reply to the analogous question regarding the transeunt action of created agents.

To be sure, this simple reply will not satisfy philosophers who, like Hume, profess to be skeptical about the notion of action in general, even as applied to God. Indeed, perhaps no reply at all will satisfy such as these. Still, it is worth noting the great epistemic weight Aristotelians assign to the common pre-analytic conviction that efficient causality /141/ abounds in the natural world.20 When Aristotelians hear the skeptical argument, propounded historically by occasionalists and positivists, that we experience at most the mere succession of what are called 'cause' and 'effect' and not the derivation of the one from the other, their typical response is astonishment. To quote Molina, "What can be more stupid than to deny what is obvious from experience and sensation?"21 Admittedly, when we begin to delve into the precise nature of the dependence of effects on their efficient causes, Aristotelians immediately rule out one of the first images that comes to mind for capturing the difference between real causality and mere succession (or counterfactual dependence), viz., the literal transfer of some ontological reality from the agent as a subject to the patient as a subject. Nonetheless--or so at least an Aristotelian will maintain--it is better to have a small dose of mystery at the end of one's analysis of the obvious rather than the large dose of implausibility that follows from denying the obvious at the very beginning. Though I accept this principle, I will not try to defend it here, since my intention has been merely to underscore the scholastic consensus that efficient causality does not involve the transfer of any entity from the agent to the patient.

We have now looked at action from the side of the agent. From the side of the patient, on the other hand, a transeunt action requires the passive reception by the patient of the agent's causal influence, with the result that a new substance or accident comes into existence and terminates the action. Suarez, echoing St. Thomas, goes so far as to claim that, in a typical case, the very same entity that is called an action insofar as it proceeds from the agent is called a passion insofar as it intrinsically modifies the patient.22 Be that as it may, we can say at least that in a typical instance of efficient causality, a passive power or potentiality that had inhered in the patient is now being reduced to actuality by the agent.

To sum up, a simple transeunt action involves at one and the same time the exercise of an active power possessed by the agent and the reception by the patient of the agent's causal influence, an influence that results in the effect, which terminates the action. The action itself is best construed as a determination belonging to the effect and thus ultimately to the patient in which the effect is produced--a determination /142/ that is identical with (or that at least results in) the effect's dependence on the agent for its coming into existence.

The competing scholastic positions on the ontology of transeunt action by and large agree with what has been said thus far. Beyond that, there are some significant disagreements. However, I will not discuss them here, since what I have already said provides enough background for the discussion that follows. Let us now turn to Durandus.


In book 2 of his commentary on the Sentences, Durandus takes up the question of whether God acts immediately in every action of a creature. After the brief opening arguments he sets the dialectical context by making explicit the rejection of occasionalism that the question takes for granted:

The question presupposes one thing and asks another. It presupposes that acting belongs to both God and creatures. Otherwise, the question would be inappropriate. And, indeed, there is no doubt as far as God is concerned ... As far as creatures are concerned, even though some at one time maintained that creatures do nothing at all, this view is now rejected by everyone ... Presupposing, then, that both God and creatures act, it is asked whether God acts immediately in every action of a creature (In Sententias Theologicas Petri Lombardi Commentariorum Libri Quattuor 2, dist. 1, a. 5, §§ 4-5).

We now have enough background to understand the exact import of this question. The key term is 'immediately'. Even though every genuine agent cause communicates esse immediately (or directly or per se) to some effect or other, it is nonetheless possible for an agent to contribute as an efficient cause to a given effect E not by directly communicating esse to E itself, but instead by directly communicating esse to another effect that stands in some appropriate per accidens causal relation to the production of E.

All parties to the present dispute agree that in every instance of creaturely action, God is an immediate (conserving) cause of the relevant agents and patients along with their active and passive causal powers. This is clear from the doctrine, accepted by all, that if God were to cease His conserving action with respect to a given entity, that entity would be totally annihilated. As St. Thomas puts it, "The esse of all creatures depends on God in such a way that ... they would be reduced to nothingness if they were not conserved in being by the action of God's /143/ power."23 Everyone agrees further that by virtue of this conserving action God is at least a mediate cause of all effects produced by created agents in their patients. However, we are now asking whether God is also an immediate cause of these effects. In other words, the question is: Does God communicate esse directly to the very same effects that, ex hypothesi, created agents directly communicate esse to?

Durandus next divides his opponents, who answer this question affirmatively, into two groups, the first of which he describes as follows:

Some claim that these effects are brought about by God insofar as they have esse, whereas they are brought about by the creature insofar as they have determinate esse. They try to argue for this claim as follows: 'Nothing is such that its whole esse has a creature as its source, since the matter, which is created by God alone, contributes to a thing's  esse. On the other hand, matter contributes nothing to the differentiation of the esse; this is done only by the form, which the creature induces in the presupposed matter. From this it follows that God, by creating the matter, acts immediately with respect to a thing's esse, whereas the creature, by contributing the form, acts immediately with respect to the thing's determinate  esse'(§ 5).

Since it is not clear how this first response can handle accidental change, let us assume for the sake of argument that it is meant to apply only to the generation of material substances, which have matter and form as essential parts or constitutive principles. And let us ask whether the resulting account of God's cooperation with secondary causes can stand as a viable version of concurrentism at least with respect to instances of generation.

Notice first that this account ostensibly appeals to a model of cooperative action that involves a division of labor. On such a model, each agent contributes independently as an immediate cause to its own distinctive effect, and the terminus of the cooperative action is just the resulting conjunction of these distinctive effects--a conjunction which, even if intended by one or both of the agents as a further end, is incidental or per accidens with respect to that which is directly aimed at in the distinct actions themselves.

Let us now apply this model, as the first response does, to the generation of a material substance--say, an armadillo. God could have produced the new armadillo by Himself, and if He had, He would have immediately produced it as a whole--both matter and form. Instead, however, He produces it in cooperation with its parents. He does this /144/ by immediately producing one effect, viz., the matter, while the secondary agents immediately produce another effect, viz., the form that actualizes the matter's potentiality for armadillohood. The resulting conjunctive effect is the new substance itself.

Unfortunately, this theory cannot be correct as it stands. First of all, as St. Thomas points out, neither the matter nor the form of a composite substance can by itself be the per se effect of a generative action; rather, it is the esse of the composite itself that is the terminus factionis, whereas the matter is that out of which the substance has its esse and the form is that by which it has its esse.24 Second, on this theory the generated composite substance would not itself have a per se cause, since there would be no single action that terminates directly in the composite substance as such--a result that is preposterous from an Aristotelian perspective. However, given our present interests, the theory's most serious defect is simply that it is not a version of concurrentism at all. As Durandus puts it:

It is obvious that [this reply] is not apropos. For it is one thing to say that God immediately produces something that exists in the creature ... It is quite another thing to say that God immediately produces each thing that a creature produces. For granted that (as they claim) the creature's action attains to the form as the terminus of its action and not to the matter, we ask whether the natural thing's very form, which the creature's action immediately attains to, is also such that God's action must attain to it immediately. They, however, go on at great length about the first point, but not about this second point ... And so their reply is not apropos (§ 6).

Recall that our question is this: Does God communicate esse directly to the very same effects that created agents also directly communicate esse to? The proposed theory purports to answer this question affirmatively. Yet according to this theory the created agents directly communicate the form of the composite substance and not the matter, whereas God directly communicates the matter and not the form. And so the first pitfall for concurrentists consists in yielding to the temptation to conceive of the effect jointly attributed to God and the secondary cause as itself a conjunction of two effects, one of which is brought about directly and independently by God and the other of which is brought about directly and independently by the secondary cause.

Still, we must try to understand exactly why this temptation is so seductive. Recall the dialectical context. Concurrentists reject occasionalism and so are committed to the claim that secondary agents can /145/ and do act as immediate efficient causes, making genuine and non-superfluous causal contributions to the effects they produce. It follows straightforwardly that God's mode of acting when He concurs with secondary causes must be distinct from any mode of acting in which He produces an effect by Himself, without the cooperation of secondary causes.25 On the other hand, concurrentists reject mere conservationism and so must hold that God's contribution to the effects of secondary causes is immediate and hence amounts to something other than the actions by which He conserves the agents and patients along with their causal powers. In sum, concurrentists are committed to the view that when God concurs with a secondary agent to produce a given effect, God's immediate causal contribution and the secondary agent's immediate causal contribution are complementary, with neither rendering the other superfluous. The philosophical problem for the concurrentist is to formulate a satisfactory metaphysical characterization of this complementarity--a characterization that will not dissolve into occasionalism by rendering the secondary cause's immediate contribution superfluous and that will not dissolve into mere conservationism by rendering God's immediate contribution superfluous. The only viable way to proceed, it seems, is to trace certain features of the effect primarily to God and certain other features primarily to the secondary agents. And the easiest way to accomplish this is to split the joint effect into two independent effects, one of which is traced back exclusively to God and the other of which is traced back exclusively to the secondary agents. The first affirmative answer succumbs to the allurement of this easy way out--with disastrous results, as we have just discovered. Let us now see whether the second affirmative answer fares any better.

Recall these lines from Durandus's characterization of the first answer:

From this it follows that God ... acts immediately with respect to a thing's esse, whereas the creature ... acts immediately with respect to the thing's determinate  esse (§ 5).

The first answer in effect reduced the distinction between esse considered by itself without further determinations (esse commune) and determinate esse to the distinction between matter and form, and then made the mistake of treating these two intrinsic essential principles as two distinct per se effects. Despite this mistake, however, the idea that the distinction between esse commune and determinate esse holds the /146/ key to a proper characterization of God's general concurrence with secondary causes finds its inspiration in St. Thomas's own discussions of creation, conservation, and secondary causality, influenced as they are by various neo-Platonic sources. Consider these representative texts:

God Himself is properly the cause in all things of the esse itself, taken in general--which is more intimate to things than anything else; it follows that God operates intimately in all things. And it is because of this that in Sacred Scripture the operations of nature are attributed to God as operating in nature (Summa Theologiae 1, q. 105, a. 5, resp.).

The primary thing in all effects is the esse; for all other things are certain determinations of it. Therefore, esse is the proper effect of the primary agent, and all other agents effect it insofar as they act in the power of the primary agent. By contrast, secondary agents, which, as it were, particularize and determine the primary agent's action, produce as their own proper effects the further perfections that serve to determine the esse (Summa Contra Gentiles 3, chap. 66).

Instances of the causing of being-taken-absolutely [ens absolute] are traced back to the first universal cause, whereas the causing of the other things which are added to the esse, or by which the esse is made specific, pertains to the secondary causes, which act by informing--presupposing, as it were, the universal cause's effect. And from this it follows ... that nothing gives esse except insofar as there exists in it a participation in the divine power (De Potentia Dei, q. 3, a. 1, resp.).

Yet St. Thomas explicitly denies that an effect produced jointly by God and creatures is a conjunction of two independently produced per se effects:

It is not the case that the same effect is attributed to a natural cause and to the divine power in such a way that it is effected partly, as it were, by God and partly by the secondary cause. Rather, the whole is effected by both of them according to different modes--just as the same effect is attributed as a /147/ whole to the instrument and also as a whole to the principal agent (Summa Contra Gentiles 3, chap. 70).

With these texts in mind, we can now move on to Durandus's characterization of the second affirmative answer:

Others hold to the same conclusion, but in a different way ... They claim that [the effects of secondary causes] are as wholes from God immediately and yet not totally, i.e., not according to every mode. They explain this by appeal to the fact that, as they put it, God acts uniformly in all things as far as He Himself is concerned, so that all the diversity in the effects is from the diversity of the things receiving the divine influence, because of the diversity of their natures. And so the effects are differentiated because they are from the secondary causes and not because of God. Thus, things exist insofar as they are from God, since in this they are not differentiated; but insofar as they have distinctive esse they are from the secondary causes, through which they are differentiated. For example, in a living thing esse [to be] and vivere [to live] are altogether the same; and so the whole is immediately from God, and the whole is also immediately from the secondary agent--but not in the same mode. For on the part of esse itself there is no distinction among things, whereas through vivere one thing is differentiated from another. For this reason, God communicates both esse and vivere, but only under the concept [sub ratione] of esse itself, in which nothing is differentiated. The creature, by contrast, communicates the whole under the concept vivere, with respect to which there is a differentiation among things (§ 7).

So one and the same effect--say, our newly conceived armadillo--is from God insofar as it exists at all, i.e., insofar as it is something rather than nothing, and from its parents insofar as its being is determinate, i.e., insofar as it is an animal of the species armadillo. In short, the effect is undivided and yet such that both its universal or general cause (God) and its particular causes (the parents) contribute to its production in distinctive and non-redundant modes. By contrast, if God had brought about the effect on His own, then He would have acted as both a universal cause and a particular cause of the new armadillo. As it stands, however, His cooperative influence is merely general or universal in the sense that He allows the natures and powers of the relevant secondary agents to determine the specific nature of the very effect which His own influence plays an essential role in bringing about. So we have singled out a mode of divine action in nature--viz., God's acting as an immediate and universal, but not particular, cause--that enables us to formulate a middle position between occasionalism, which in /148/ essence holds that God is a particular cause of every effect produced in nature, and mere conservationism, which denies that God is an immediate cause of the effects produced by secondary agents. Or so, at least, the second answer affirms.

Durandus, however, takes this answer to involve a perversion of Aristotle's distinction between universal and particular causes. This distinction, he contends, is wholly a distinction among the various descriptions that are truly predicable of one and the same cause of a given effect--and not a distinction among really distinct causes of the same effect:

[In Aristotle's example] one who makes a statue is a cause of a statue, while this man is a cause of this statue--so that, just as a statue and this statue differ not in reality but only conceptually, so too they are traced back to causes that are diverse not in reality but only conceptually, as are a sculptor and this sculptor. And similarly in the case under discussion, since within one and the same thing esse and vivere differ only conceptually, they should be traced back to causes that differ only conceptually, so that there is in reality just one cause that gives esse and vivere immediately, but under diverse concepts. That is, it gives esse insofar as it itself is an actual being and the other thing exists only potentially; and it gives vivere insofar as it is actually living and the other thing has life [only] potentially ... And so it is not necessary that esse and vivere, which differ conceptually within the same entity, should be traced back immediately to causes that are really diverse, viz.,vivere to the secondary cause and esse to the First Cause, i.e., God (§ 10).

It is here, however, that Durandus's argument fails to convince--and this independently of questions about how Aristotle should be interpreted. For it is not difficult to think of examples in which various truths about the unitary effect of a cooperative action might plausibly be thought to derive primarily from one of the agents rather than another. In presenting these examples, I do not mean to suggest that by themselves they provide wholly adequate models for God's concurrence with secondary agents or even that they are flawless on their own terms. My purpose is merely to open up some of the conceptual space that Durandus is trying to close off preemptively.

The most obvious examples trade on St. Thomas's claim that God's relation to secondary agents is in relevant respects similar to a principal agent's relation to its instruments. Suppose that in lecturing on Socrates's conversation with Meno's slave, I use a piece of blue chalk to draw a square on the blackboard. It seems clear that both the chalk and I count as joint immediate causes of a single effect, viz., the blue square-shaped line that appears on the surface of the blackboard. Yet the fact /149/ that the line is blue, rather than some other color, is traced back primarily to the causal properties of the chalk as an immediate instrumental cause of the blue square rather than to any of my properties as an immediate principal cause of the blue square.26 By the same token, the fact that there is a square-shaped effect--rather than, say, a circular effect or no effect at all--is traced back primarily to my influence as an immediate principal cause and not to the chalk's as an instrumental cause.

Still, we need not invoke either the distinction between universal and particular causes or the distinction between principal and instrumental causes in order to illustrate that cooperative effects sometimes have features that can be traced back primarily to one or another of the cooperating agents without destroying the unity of the effect. Suppose that the temperature is -20° F and you ask a friend to help you lift the rear end of your stalled car over a ridge of ice that has formed in your driveway, so that you can then push the car into the relative safety of your garage. And suppose that you take hold of the left rear bumper and that your equally strong friend takes hold of the right rear bumper, and that together you lift the car the required ten inches off the ground, so that as a whole it acquires a new accidental determination, viz., a new spatial location. In that case each of you is a particular cause of this unitary effect, since neither of you can be said to channel or determine the power of the other. Yet even if neither of you could have lifted the car so much as an inch off the ground on your own, it still seems natural enough to say that the fact that the left rear part of the car now stands ten inches off the ground--instead of, say, six inches or none at all--is traceable primarily to you as an efficient cause rather than to your friend, and this in virtue of the fact that you are lifting from the left side. (After all, if you had both been lifting from the right side, the left rear part of the car would not have been raised.)

There are also interesting cases in which the 'cooperating' agents exercise contrary powers. To borrow an example from Peter Geach, suppose that heating unit A and cooling unit B act together to raise the temperature of a room by 15° F--to, say, 75° F--in one hour, whereas A by itself would have raised the temperature by 25° F in the same time, and B by itself would have lowered temperature by 10°. In this case it seems plausible to say that even though the joint effect is produced as a whole by both A and B together, the fact that the temperature after one hour is 75° F rather than 85° F is traceable primarily to B, whereas the /150/ fact that the temperature after one hour is 75° F rather than 50° F is traceable primarily to A.

So Durandus's objection to the second affirmative answer is not compelling as it stands. Given the force of the above examples, it is not obviously implausible to claim that in any given instance of secondary causality, the fact that the unitary effect is something rather than nothing is traceable primarily to God as a universal cause, whereas the fact that the unitary effect is of one determinate kind rather than another is traceable primarily to the secondary causes. Admittedly, these claims need to be articulated with more philosophical rigor. What is it, exactly, for a given feature of a joint effect to be traced back primarily to just one of the cooperating causes rather than to another? More fundamentally, what exactly is a 'feature', and how is it that we seem able to invoke such features without splitting the effect and thus succumbing to the first pitfall? As is only appropriate when one does not have the answers, I will leave these questions for further reflection. Nonetheless, the prospects are not at all bleak. Perhaps features are best thought of as facts or states of affairs that involve (variously) the effect, the circumstances of the effect's production, and the causal properties of the relevant agents and patients. And perhaps we can say that even though the cooperating causes communicate the very same esse to a unitary effect, each is nonetheless primarily responsible for different facts or states of affairs involving that effect. I hope to pursue this line of thought more deeply in the future.27

Durandus's discussion, then, has served to focus our attention on a possible pitfall for concurrentist theories, but has failed to show that no such theory can succeed. What remains is to find a philosophically rigorous characterization of the idea that features of a unitary joint effect can be traced back primarily to one or another of the cooperating /151/ causes without destroying the unity of the effect. And the prospects for success are fairly bright.


The first pitfall had to do with the effect produced jointly by God and the secondary agents. The second concerns the agency by which that effect is produced. Durandus poses the pertinent issue as a dilemma for the concurrentist: "If God acted immediately in the production of the effect of a secondary cause, then He would act either by the same action as that by which the creature acts or by a different action" (§ 11). Predictably enough, Durandus contends that both alternatives lead the concurrentist to ruin. My strategy here will be, first, to show that concurrentists must embrace the thesis that when God and creatures cooperate, they act by means of one and the same action, and, second, to argue that Durandus's objection to this thesis is not compelling. As the discussion proceeds, it will also become clear, I hope, why this relatively esoteric ontological issue is important not only for the treatment of God's general concurrence but, more broadly, for the philosophical analysis of cooperative action in general.

Notice, to begin with, that any concurrentist who has already succumbed to the first pitfall by splitting the joint effect into two more basic effects is thereby committed to the claim that when they cooperate with one another, God and creatures act by distinct actions. For, as noted above, distinctness among per se effects is a sufficient condition for the distinctness of the actions that produce those effects.

Still, it is not yet clear why a concurrentist who holds that God and secondary agents immediately produce a unitary effect should reject the idea that God's action is distinct from the action of the secondary causes. I will now argue, however, that the only general models of cooperative action that can, on the surface at least, be plausibly thought to combine sameness of per se effect with a plurality of actions are unsuitable as models for God's concurrence with secondary causes. I will briefly examine four such models.

The first is a species of causal overdetermination that is sometimes called causal redundancy. On this model, (a) a unitary effect is produced by two distinct actions and (b) each of the actions is such that it would have produced that very same effect in the absence of the other action. Philosophers--both medieval and contemporary--have disagreed about whether causal redundancy as so defined is even possible,28 but however /152/ one might decide that question, it is obvious at any rate that this first model is incompatible with concurrentism. For, first of all, concurrentism holds that secondary agents are incapable of producing any effects at all without God's general concurrence. And, second, as we saw above, concurrentists also assert that when God acts as a general concurring cause, His influence is not by itself--independently of the influence of the secondary agents--sufficient to produce the effect. Or, to put it more accurately, God's actual influence in the mode of concurring simply does not exist in the absence of the secondary cause's influence. In short, the two are necessarily complementary.

These very same considerations also serve to undermine the usefulness of the second and third general models of cooperative action that might initially be thought of as involving two distinct actions. On the second model, (a) a unitary effect is produced by two distinct actions, but (b) just one of those actions, and not the other, would have been sufficient by itself to produce the very same effect. Once again, according to concurrentism, when God concurs with secondary agents to produce an effect, neither God's action nor the secondary cause's action can even exist in the absence of the other, and so neither can be sufficient to produce the effect in the absence of the other. (This is not, of course, to deny that God could have produced the very same effect on His own; but in that case He would have acted as a particular cause and not as a general concurring cause.)

The third model, on the other hand, is such that (a) a unitary effect is produced by two distinct actions, (b) neither of these actions would by itself have produced that same effect, but (c) each of the agents, by exercising the very same power that it in fact exercised in the actual case, would have produced some alternative effect in the absence of the other agent's action. There are two interestingly different cases here. In the first, each agent, acting without the other, would have produced a less intense effect of the same species. For instance, two light sources have actually produced an illumination of degree n, but each, in the absence of the other, would have produced an illumination of some degree less than n. In the second case, each agent, acting without the other, would have produced an effect opposed to the effect that would have been produced by the other agent acting by itself. The example, introduced above, of heating unit A and cooling unit B is a case of this type.

Obviously, neither sort of case can model divine concurrence, since according to concurrentism neither God's influence nor the secondary agent's influence so much as exists in the absence of the other. Still, we might usefully probe a bit deeper by asking just how plausible it is, upon /153/ reflection, to assert that in cases that seem initially to fall under the third model there are two distinct actions rather than just a single action. Remember that an action just is (or at least necessarily results in) an effect's dependence on its cause. Now recall the case of heating agent A and cooling agent B and assume for the purposes of argument that B's action is distinct from A's even though they produce a unitary effect--viz., a room temperature of 75° F, which constitutes a 15° F increase over one hour. Since the effect is unitary, each of the two allegedly distinct actions, viz., A's action and B's action, must terminate in that same effect. But from this it follows that cooling agent B's action, taken in itself as distinct from A's action, is a per se cause of the room's temperature increasing by 15° F to 75° F--an implication that, to put it mildly, is incredible, since the effect is wholly disproportionate to the agent's power. It is much more plausible to say instead that A and B together constitute a single total agent which, by a single action, raises the temperature by 15° F--an effect that is indeed proportionate to the power of this single total agent. In short, our initial assumption that there are two distinct actions has been completely undermined. In cases of this sort there is just a single dependence of the effect on a single total cause (even if that cause includes several agents), and so too there is just a single action terminating in an effect proportionate to the power of that total cause. A similar, though less striking, analysis can be given of the example involving the two light-sources.29

The same conclusions will hold, a fortiori, for a fourth model of cooperative action on which neither of the two actions would effect anything--or, better, even exist--in the absence of the other. To revert to an earlier example, suppose that neither you nor your friend can lift the rear end of the car at all, but that the two of you together can lift it ten inches off the ground. If your actions were distinct in this case, then each of those actions would terminate in an effect that neither of them is capable of producing. Once again, then, the effect would be wholly disproportionate to the allegedly distinct actions, and so it is more reasonable to hold that when you act together to lift the car, the two of you act by the same action.

This fourth model is, of course, a fitting one for the concurrentist, since according to concurrentism neither God's concurrence nor the secondary cause's influence can effect anything, or even exist, in the absence of the other. So the concurrentist must hold that in their cooperative actions God and the secondary cause constitute a single total /154/ cause that produces the relevant unitary effect by means of a single, undivided, action.30

This position dovetails quite nicely with an ontological account of action, like that propounded above, according to which an action is the effect's dependence on the agent during the time when it is being produced. For this dependence can be unitary even if the cooperating agents are distinct from one another, as long as those agents together constitute a total immediate cause of the effect. For in that case, the cooperating agents act as a unitary agent with a single, combined, power that is proportionate to the effect.31

Indeed, the temptation to divide all cooperative actions into a plurality of distinct actions stems almost entirely--or so it seems to me--from the initial seductiveness of certain ontological accounts of action which turn out to be inadequate precisely because they are formulated without due reflection on cooperative action in general and, more specifically, on the third and fourth models of cooperative action just described. Take, for instance, those accounts according to which actions are intrinsic determinations or accidents of the agents whose actions they are. On such accounts it follows straightforwardly that if A and B are distinct substances, then no action of A's can be identical with any action of B's, since A's actions, but not B's actions, have  A as their ontological subject. Again, suppose that, in a more contemporary idiom, one takes as the primitive causal locution something like 'Agent  A causally contributes to state of affairs S at time t', and suppose further that one identifies A's actions with states of affairs of the form A's causally contributing to S at t. Then, since for any two distinct substances X and Y the state of affairs X's causally contributing to S at t is admittedly distinct from the corresponding state of affairs Y's causally contributing to S at t, they must be two distinct actions even if they involve the very same effect. /155/ By now we have seen enough to be wary of any such account of the ontology of action.

It remains only to deal with Durandus's objection to the claim that God and secondary agents immediately cause a given effect by means of the same action. The objection trades on an ambiguity in the Latin term perfectum, with the result that the concurrentist is accused of holding a thesis which, to invoke one of the traditional terms of theological censure, is at the very least ill-sounding, viz., that God's concurrence is in some way imperfect:

It is possible for numerically the same action to be immediately from two agents but from neither perfectly (perfecte), as when two people are dragging a boat or when two candles are causing one light; for the movement of the boat is not completely from either one, and the illumination of the air is not from either candle by itself and perfectly. In such cases two imperfect agents (agentia imperfecta) take the place of one perfect agent. But there appears to be no possible way for the action to be immediately and perfectly from each without its being the case that numerically the same principle or numerically the same power is in both of them (§ 12).

Here is Suarez's somewhat more lucid restatement of the objection: It is impossible that two agents should immediately concur with respect to the same action unless each of them is an imperfect (imperfectum) and only partial agent--which should not be said of God. Therefore, God does not immediately concur with a creature with respect to its action (Disputationes Metaphysicae 22, sect. 1, § 4).

The problem is that the term perfectum can mean 'complete' as well as 'perfect', and we have already noted that the concurrentist holds that when God acts in the mode of general concurrence, His own contribution to the effect complements that of the secondary cause and is not of itself sufficient to bring about the effect. So it is only together that God and the secondary agent constitute a complete or 'perfect' cause of the effect. It follows that each is, in its own right, only a partial or incomplete--and in that sense 'imperfect'--cause of the effect. However, it seems obvious that to call God an imperfect agent in this sense hardly derogates the divine nature.

My own inclination is therefore simply to dismiss the objection as a terminological ploy. Nonetheless, many scholastic thinkers were reluctant to call God a merely partial or imperfect cause of the effects that He brings about with secondary causes. Suarez's own response to the /156/ objection makes allowance for this reluctance and is hence more sagacious than the one I am inclined toward:

The other [alleged] difficulty is that [God and the secondary cause] would be partial agents ... Some concede this inference, since if one simply considers the entire effective causality that is necessary for the effect, then neither of of both causes ... By contrast, others think that the inference should be denied because, given that the two causes belong to diverse orders, they are not properly said to compose a single total cause; rather, each is an entire cause within its own order. This way of speaking seems more acceptable, both because it is more common and also because it is more apt to indicate the inequality and ordering between these causes (Disputationes Metaphysicae 22, sect. 1, § 22).

But whichever side one comes down on here, Durandus's objection has once again fallen far short of being compelling, even though, as before, his discussion has served to heighten our awareness of a possible pitfall for concurrentism.


Our examination of Durandus's treatment of concurrentism has been fruitful in at least two ways. First and most obviously, it has enabled us to identify the two pitfalls of the conjunctive effect and the divided action. Second, it has served to put into relief some of the difficult ontological issues in the theory of action that any attempt to construct an adequate version of concurrentism will have to come to terms with. Despite the current revival of interest in philosophical theology among Anglo-American philosophers, and despite the fact that a viable account of how God acts in nature is a crucial component of any metaphysical system that would comport with Christian doctrine, the recent work on this topic has, to my mind, not been sufficiently sensitive to the historical origins of the debate over secondary causality or sufficiently cognizant of the depths of the scholastic contributions to it. My hope is that the present paper will serve as a partial remedy for these deficiencies and that it will provide some semblance of a foundation for future attempts to articulate a coherent version of concurrentism that will have some purchase on contemporary Christian philosophers.


1. Here is how St. Thomas explains God's threefold existence in things: "[God] is in all things through His power, insofar as all things are subject to His power. He is in all things through His presence, insofar as all things are uncovered and exposed to His sight. He is in all things through His essence, insofar as He comes to all things as the cause of their being" (Summa Theologiae 1, q. 8, a. 3, resp.).

2. Eduardo Iglesias, S.J., De Deo in Operatione Naturae vel Voluntatis Operante (Mexico City: Buena Prensa, 1946), p. 102. I am indebted to James Sadowsky, S.J., for calling this book to my attention.

3. On this score Aristotelianism differs from the view held by many contemporary metaphysicians who, like Aristotelians, wish to propound a robust account of human freedom. For the metaphysicians in question tend to distinguish sharply between agent causality, which is found only among rational beings, and event causality, which is ubiquitous. Such a framework generates the artificial and (to my mind) intractable problem of how the two types of causality are related to one another in the case of free human action.

4. For more on occasional causality, see my "Medieval Aristotelianism and the Case against Secondary Causation in Nature," pp. 74-118 in Thomas V. Morris, ed., Divine and Human Action: Essays in the Metaphysics of Theism (Ithaca, NY: Cornell University Press, 1988), esp. section 3. Inspired in part by Malebranche's occasionalism, Hume propounded a secular version of this reduction of causal dependence to counterfactual dependence. Interestingly, such a position has become extremely influential in contemporary analytical metaphysics, mainly through the work of David Lewis. See especially "Causation" and "Postscripts to 'Causation'," pp. 159-269 in David Lewis, Philosophical Papers, vol. 2, (Oxford: Oxford University Press, 1986).

5. For more on this, see "Medieval Aristotelianism and the Case against Secondary Causation in Nature." The anti-realism I have in mind is evident, for example, in Lewis's counterfactual analysis of causality, as well as in Bas van Fraassen's scientific anti-realism, which agrees with occasionalism in denying that the purpose of natural science is to discover the "real causes" operative in nature. See van Fraassen, The Scientific Image (Oxford: Oxford University Press, 1980).

6. See my "God's General Concurrence with Secondary Causes: Why Conservation is Not Enough," Philosophical Perspectives 5 (1991): 553-585.

7. Eduardo Iglesias, S.J., is the only twentieth-century neo-scholastic I have found who is willing to defend mere conservationism explicitly and in detail. See his De Deo in Operatione Naturae vel Voluntatis Operante. Iglesias goes so far as to attribute this position to St. Thomas--an attribution that seems utterly wrong-headed to me. Still, in fairness to Fr. Iglesias, I plan to examine his arguments carefully in my future work on divine action.

8. The term 'general concurrence' signifies God's influence on the effect itself rather than on the agent. Within the scholastic debate over secondary causality one hotly disputed question is whether God acts on the secondary agent itself in contributing to its effect. Many Thomists answer affirmatively, positing variously that God moves the secondary cause to act, or that He applies it to acting, or that he excites or stirs up its power, or that He uses it as an instrument. Each of these locutions seems to imply that God acts on the secondary cause prior to--at least naturally prior to--the secondary cause's own action on its patient. By contrast, the Jesuits deny that there is any such antecedent divine action on the secondary cause itself. (For an illuminating (For an illuminating discussion, see Francisco Suarez, Disputationes Metaphysicae, disp. 22, sect. 2.) Here I wish to avoid this issue, focussing instead on the claim that God is an immediate cause of the effects of secondary agents--a claim that all the Thomists accept under some interpretation. It is this immediate causal influence on the effect that I am calling God's general concurrence.

9. Relevant works include Domingo Bañez, O.P., Scholastica Commentaria in Primam Partem Angelici Doctoris Divi Thomas Aquinatis (Salamanca, 1584 and 1588), modern edition edited by Luis Urbano, S.J. (Madrid, 1934); Luis de Molina, S.J., Liberi Arbitrii cum Gratiae Donis, Divina Praescientia, Providentia, Praedestinatione et Reprobatione Concordia (2nd edition: Antwerp, 1595), modern edition edited by Johann Rabeneck, S.J. (Oña and Madrid, 1953); and Francisco Suarez, Disputationes Metaphysicae (Salamanca, 1597), modern edition edited by Carolo Berton as vols. 25 and 26 of Suarez, Opera Omnia: Nova Editio (Paris, 1866; reprinted in two volumes at Hildesheim, 1965).

10. When my exposition of transeunt action strays into controversial matters, I will be following Suarez, Disputationes Metaphysicae, disp. 18, sect. 10; disp. 48; and disp. 49.

11. For the sake of simplicity, in what follows I will speak simply of production, since production, rather than conservation, is the focus of the disputes over God's concurrence.

12. One reason St. Thomas uses 'esse' here instead of 'form' is to accommodate the possibility of the creation ex nihilo of material substances, where the matter perfected by the relevant form is itself brought into existence. According to St. Thomas, when a material substance is created ex nihilo, its matter is 'co-created' along with it. So even though the matter cannot exist on its own without any formal determinations and so cannot be the per se terminus of God's creative act, it nonetheless "pertains to being" and so must itself be thought of as something that is communicated or bestowed when a material substance is created ex nihilo. See Summa Theologiae 1, q. 44, a. 2, resp.

13. St. Thomas's distinction between esse and essence is not a distinction between entities, since the essence is not a limiting principle except insofar as it is 'already' actual. Rather, the ground for the distinction lies in the fact that (a) there is nothing about the actualized essence that requires that it or any of its parts should be something rather than nothing, and that thus (b) a finite essence, with all its parts, must owe its existence to causes outside itself. I take this interpretation to be consonant with that proposed by Charles Hart in Thomistic Metaphysics: An Inquiry into the Act of Existing (Englewood Cliffs, NJ: Prentice-Hall, 1959), pp. 86-92.

14. Among the scholastics there are numerous disagreements about the ontological status of accidents. The accounts range from the highly inflationary, according to which all (or almost all) accidental terms designate distinct dependent entities that could, at least by God's power, exist without inhering in any substance, to the highly deflationary, according to which all (or almost all) accidental terms designate modes or states that cannot exist, even by God's power, without inhering in some substance. I will ignore this dispute here and assume that even on the most deflationary accounts we can still think of modes of substances as themselves instances of esse and thus appropriate termini for exercises of efficient causality. On accidents (or accidental esse) as the termini of efficient causality, see Barry Brown, Accidental Being: A Study in the Metaphysics of St. Thomas Aquinas (New York: University Press of America, 1985), esp. pp. 224-227.

15. Scholastica Commentaria in Primam Partem Angelic Doctoris Divi Thomas Aquinatis, q. 104, a. 2, column 1974, C and E.

16. This is not, of course, to deny that certain agents, viz., material substances, undergo internal changes when they act--e.g., loss of energy. It is, however, to deny that such internal changes in the agent belong to the very nature of a transe action as such.

17. The term 'proper effect' is meant to distinguish the per se effects of actions from accidental conjunctions of effects, where the conjunction itself has no per se cause as such.

18. I ignore for now the complications raised by human actions that are omissions, since such "actions" presuppose cognitive powers that are lacking in non-rational creatures.

19. See, e.g., the following selections from G.W. Leibniz, Philosophical Essays, edited and translated by Roger Ariew and Daniel Garber (Indianapolis, IN: Hackett Publishing Co., 1989): "Primary Truths," pp. 30-34; "Discourse of Metaphysics", pp. 35-68, esp. pp. 46-49; and "To Arnauld (April 30, 1687)", pp. 81-90. Notice that Leibniz's objection applies equally well to local motion. The fact that we talk glibly about the "transfer of energy" from mover to thing moved should not obscure the fact that variations in energy levels that result from the collision of physical bodies are metaphysically on a par with other qualitative and quantitative modifications. Indeed, such "transfers" can be accepted with equanimity by occasionalists without any admission that real action has occurred in nature.

20. For more on the 'ordinary' concept of causality, see Elizabeth Anscombe's "Causality and Determination," in Ernest Sosa, ed., Causation and Conditionals (Oxford: Oxford University Press, 1975), pp. 63-81.

21. Molina, Concordia, Part II, disp. 25, § 5.

22. See Suarez, Disputationes Metaphysicae, disp. 49, sect. 1, § 8. There he alludes to the following passage from St. Thomas, In XII Libros Metaphysicorum Expositio XI, lect. 9: "Action and passion are the same in substance ... Motion constitutes the category of passion insofar as it is predicated of the subject in which it exists, whereas it constitutes the category of action insofar as it is predicated of that from which it exists."

23. Summa Theologiae 1, q. 104, a. 1, resp.

24. See, e.g., De Potentia Dei, q. 3, a. 8, resp., and Summa Theologiae 1, q. 44, a. 2.

25. God could produce the effects by Himself in either one of two modes, viz., by creating them ex nihilo along with their material causes, or by miraculously educing the relevant forms by Himself from preexisting material causes.

26. True, I could have chosen a different color of chalk. But this is incidental to the specific nature of the effect that is in fact produced when I use the blue chalk.

27. It is worth noting that an Aristotelian account of efficient causality, according to which the esse of an entity (substance or accident) is the terminus of the causal relation, has a decided advantage here over a popular contemporary account according to which the terminus of the causal relation is a state of affairs. For if, as I am inclined to think, any coherent version of concurrentism will acknowledge that God and secondary agents are primarily responsible for different facts or states of affairs involving the termini of causal relations, then it will be enormously difficult to state the concurrentist thesis in terms of the contemporary account without immediately splitting the effect--as one would by claiming that whereas God brings it about that entity x exists at time t, the secondary agent brings it about that x has property P at t. I believe that this problem is apparent in the account of divine causality worked out by my colleague Philip Quinn in "Divine Conservation, Secondary Causes, and Occasionalism," pp. 50-73 in Divine and Human Action: Essays in the Metaphysics of Theism.

28. Medieval philosophers debate this issue in their discussions of whether one effect can have two 'total' causes. See Suarez, Disputationes Metaphysicae, disp. 26, sect. 4. The possibility of this sort of simultaneous overdetermination poses a special problem for theories of causality which, like David Lewis's, reduce causal dependence to a form of counterfactual dependence. See Lewis, "Postscripts to 'Causation'," esp. pp. 193-212.

29. Here the surprising conclusion would be that a light-source which itself has the power to illuminate the room only to a degree less than n is such that its action, distinct from that of the other light-source, terminates in an illumination of degree n.

30. Other considerations lead to the same conclusion. The most obvious is that, as Suarez points out in arguing against mere conservationism (Disputationes Metaphysicae, disp. 22, sect. 1, § 9), the secondary cause's action is itself a finite or participated entity and hence must depend immediately on God for its being. However, it is difficult to see how this dependence can hold if God's action is distinct from the secondary cause's action. For, as all our authors agree, an action cannot itself be the per se terminus of another action; otherwise, an infinite regress of actions would be generated whenever any agent acted. There are also theological reasons for insisting that when God and creatures cooperate to produce a joint effect, they do so by the same action. First, many of the sacred texts cited by occasionalists straightforwardly attribute to God the actions of causes in nature. Second, the doctrine of habitual (or sanctifying) grace seems to require that meritorious actions be attributed directly to God as well as to the relevant free creatures.

31. This is at least part of what St. Thomas has in mind when he claims that lower agents act not only by their own power but also by the power of all the superior agents to which they are subordinated. See, e.g., Summa Contra Gentiles 3, chap. 70.