§ 34.
1. Plato dissociated intellectual knowledge from experience, and made the latter the occasion which gave rise to knowledge. Aristotle, on the other hand, makes experience the foundation of all intellectual knowledge, and lays it down as a principle that intellectual cognition has its source exclusively in experience. "Nihil in intellectu quod prius non fuerit in sensu" -- this is the fundamental principle of the Aristotelian Theory of Knowledge, as it is also the point at which the fundamental difference between the views of Plato and Aristotle begins. Without sense, intellectual knowledge is impossible. Experience is, therefore, the basis and source of all intellectual cognition, i.e., of all science.
2. In experience, however, we have to do only with individual objects. The world of sense, which is the world of experience, consists wholly of single objects or individuals (ex adiairetôn ara to pan, Eth. Nic. VI. c. 12.) It follows that the individual is that which comes first in our knowledge, and that it is only in a second stage we pass from the individual to the general. Intellectual knowledge, knowledge properly so called, is concerned only with the general, and this knowledge has its source in experience; experience, however, brings us into contact only with the individual; it follows that what in our knowledge is general, must be evolved from the individual, Of its nature, then, the universal takes precedence of the individual, and is more an object of knowledge; but for us the individual comes first, is more immediately the object of knowledge, and from it we must set out in order to reach the universal. Plato takes the universal, the Idea, as the point of departure in his attempt to explain by an a priori method the existence of individual things, and to form a philosophical conception of the world as a whole. Aristotle, on the contrary, begins with the individual, and endeavours by a posteriori methods to derive from this the universal, and thus to arrive at a philosophical comprehension of the universe. Herein we have a second fundamental difference between the systems of Plato and Aristotle.
3. It follows from the principles thus laid down by Aristotle that the universal is not something standing apart from the individual; in other words, the universal cannot be regarded as having being of its own really distinct from the being of the several individual objects. In such a supposition it would be impossible to derive the universal from the individual. The universal must be immanent in the individual; this is the only supposition on which a progress in thought from the individual to the universal becomes possible. Wbilst, then, Plato separates the universal from the individual, and establishes a real distinction between them, Aristotle emphatically asserts the doctrine that the universal is in the individual, not without it. This constitutes the third fundamental difference between Plato's Theory of Knowledge and that of Aristotle.
4. The universal existing in the individual, not apart from it, it follows, according to the reasoning of Aristotle, that, as invested with the formal character of universality which it possesses in our thought, it cannot be objectively real. The universal is that which is common to the several individual objects, viz., that which can be predicated of all alike. It is not a single entity in itself, it is merely a "predicabile de multis." What we find existing in a number of different objects, what these objects all alike possess, and what we can, in consequence, predicate of them all, is an universal. If, then, we wish to define the universal, we must describe it as that which of its nature is such that it can be predicated of many individual things. We see then that whereas Plato holds the universal, taken formally in its universality, to be objectively real, Aristotle will admit the material entity represented under this form of universality, to be objectively real, but will by no means admit this objective reality to be a single universal being. And here we have the fourth essential difference between the Platonic and Aristotelian Theory of Knowledge.
5. On the principles here set forth rest the whole Logic and Noetic of Aristotle. We proceed to the exposition of his logical and noetical system, as based upon these principles. It will be made clear to us as we advance, that Aristotle does not understand the principles quoted, in the sense of the empiricist or nominalist, though this might appear at first sight to be the case. It will be seen that his theory of knowledge avoids Empiricism and Ideallsm alike, and finds a middle course between the two extremes, which secures at once the rights of Reason and of Experience.
6. The psychological assumption underlying Aristotle's Theory of Knowledge is the essential difference between Sense and Intellect, between sensuous perception and thought (aisthêsis and noêsis.) Sense and Intellect, sensuous perception and thought, are not to be made one; they must be taken as essentially different functions; Sense is concerned with the sensible (to aisthêton), Intellect has to do with the supersensible (to noêton); Sense has for its object the individual, Intellect, the universal. The two classes of objects being essentially different, the corresponding faculties must be regarded as essentially different sources of knowledge.
7. This being premised, the question arises: In what way does the Intellect pass from the individual object which appears in the sensuous perception to the universal? To answer this question Aristotle has recourse to the distinction between the ousia prôtê and the ousia deutera, and with the help of this distinction he unfolds his theory as follows:
(a) First in order, says Aristotle, we have substance (ousia prôtê) -- that which does not exist in anything else, and which cannot be predicated of anything else, but in which all else exists, and of which all else can be predicated. This notion, it is clear, can be applied only to the individual object, for the individual is not a predicament, but is rather the subject in which the predicaments have existence; what does not exist in the individual has no existence at all. The individual must therefore be described as the ousia prôtê (substantia prima.)
(b) Examining more closely this ousia prôtê we distinguish in each individual two constituent elements -- a real substratum (hupokeimenon) of being, and another element by which it is made to be that individual which is actually presented to us (eidos). The former is the determined element, the latter the determining. The former is the substratum of the Idea, the latter is the Idea itself as realized in the individual. The former is Matter (hulê), the latter is Form (morphê). United they form the constituent principles of individual being, of the ousia prôtê. Without these two principles the ousia prôtê is unthinkable.{1}
(c) Keeping in view the distinction here laid down, we are led at once to the notion of the ousia deutera. The Form, being that by which the individual is made to be what it is, is the thing which we call the Essence of the individual. This essence is something more than the permanent unchanging element in the being of the individual; it is, at the same time, the basis of all its attributes; it is of the essence that all the properties or attributes which in any way belong to the individual are predicated. It thus becomes identified with the Substance of the Individual. This Substance of individual being, which is identical with its Essence, is the ousia deutera.
(d) The notions ousia prôtê and ousia deutera being thus defined, the question next arises: What are the relations of the one to the other? If the ousia deutera be no more than the determining principle in the individual being, it follows that the question what the individual is can be answered only by assigning its ousia deutera. The latter, in the words of Aristotle, is therefore the to ti ên einai of the former, or its quiddity (quid est). Hence the notions morphê, eidos, ousia deutero, to ti ên einai, as applied to the individual, represent, according to Aristotle, one and the same thing.
(e) Comparing several individuals, in point of quiddity or to ti ên einai, we find several individuals to have the same quiddity -- to be such that the same to ti ên einai must be asserted of all of them. Thus, for example, all human individuals, when compared together, are found to have the same quiddity, the same to ti ên einai, the same ousia deutera, for each man stands on the same level of nature with all other men, possesses a being determined by the same essential ebaracteristics. From this it follows that the same quiddity or ousia deutera can be common to several individuals in this sense that each of these individuals has a like quiddity or ousia deutera with the rest.
(f) On the other hand, the second constituent principle of the ousia prôtê, Matter, is of such a nature that it can never, in any way, be common to several individuals. Matter, as the substratum of the quiddity or determinate being of a given individual, belongs exclusively to the individual in question; it can in no wise be shared with another, and precisely for the reason that the Matter belonging to the individual is exclusively its own, is the individual distinct from all other individuals, and possessed of completed being in itself.
(g) From this it follows that in the individual Form (the ousia protera or to ti ên einai) is the principle of Specification; Matter, or the hupokeimenon, the principle of Individuation. The Form or quiddity being the same in several individuals, unites these individuals into one species: Matter being different in each individual, determines the individuality of each to the exclusion of all the others. On the Form or quiddity -- the principle of specification, depends the unity of several individuals in one species; on the Matter -- the principle of individuation, depends the plurality of individuals within the same species.
(h) We are now in a position to give an answer to the question: How does thought rise from the particular to the Universal? The faculty of sense puts before us the individual object as it appears individually in the world of phenomena; thought penetrates to the Form, ousia or quiddity, underlying the individual, abstracts this from the individual, and makes it the object of its thinking activity. The ousia thus apprehended as an abstraction, we again predicate of the individual, attributing it to the individual as its proper quiddity. We next come to perceive that this quiddity belongs not to one individual merely -- that a number of individuals possess a quiddity like the first; this quiddity, which our thought thus represents as common to many individuals, we naturally conceive of as predicable of many individuals, i.e., we conceive of it as universal, and we unite under this common concept all the individuals of which the ousia in question is predicable. By this perfectly natural process are we led from the individual to the universal.
8. In this process three further points are worthy of note:
(a) In the first place it is clear that according to the mind of Aristotle the universal is not merely an ens rationis, a purely notional entity; the thing represented in the concept is objectively real in the several individuals, for it is nothing else than the ousia or quiddity of these individuals. It is only in so far as this ousia is thought as universal, that it can be called a product of thought, and even in this respect the procedure of thought cannot be said to be arbitrary, for it rests upon that likeness of the ousia in the several individuals which exists as an objective fact.
(b) In the second place it becomes evident how and in what sense Aristotle was led to assert that the universal is inseparable from the individual; that it is indwelling (immanent) (enuparchon) in the individual. For the ousia deutera has not independent existence, it exists in the individual or ousia prôtê as the quiddity of the latter; and this ousia deutera is the thing represented in the universal notion.
(c) In the third place it becomes apparent why and in what sense Aristotle asserted that the universal, taken objectively, is not one single being, that in the objective order it manifests itself only in different individuals. For every individual, owing to the material element included in it, is a being completed in itself, and the common possession of the ousia by several individuals, is not to be regarded as constituting oneness in being, but only as implying a likeness of ousia between many individuals.
9. Having now set forth the fundamental principles of Aristotle's theory of Knowledge, we pass on to his Logic. What we have first to notice here is the place assigned to the Concept. The Concept (logos), according to Aristotle, has to do with the Essence (ousia) of things. When our thought represents the Essence of things in abstracto, it represents it in the form of a Concept. It follows that the universal, as such, exists only as an universal Concept in the thinking mind. The determination and exposition of the Concept (horismos) is effected by Definition. Definition is, therefore, nothing more than the exposition of the Essence of a thing.
10. If we consider closely any concept which represents the Essence of certain things to the exclusion of all others, we shall distinguish in it two elements, a general and a special. The general is possessed by the individuals included under the given concept in common with certain other individuals, the special element is peculiar to the former individuals and serves to distinguish them from the latter. The general element is the common element, the special is the differentiating element (Difference). The general is the indeterminate, the special is the determining element; and they may, therefore, be regarded as standing to one another in the relation of Matter and Form.
11. It is owing to this distinction between the elements of our concepts that our conceptual knowledge does not stop at the first specific differences of things; we are led to subordinate particular concepts to more general concepts. For the characteristics which are common to several concepts can be conceived, per abstractionem, only as themselves forming a concept7 and thus we have a higher concept under which the first are subsumed. In this way we proceed from the Specific to the Generic concept, from the Species to the Genus. If we push this process of abstraction to the utmost limit permitted by our concepts, we arrive at ultimate generic notions which cannot be subordinated to (subsumed under) any others: i.e., we arrive at the so-called Categories.
12. Aristotle enumerates ten categories, or ultimate generic notions (suprema genera): Substance (ousia), Quantity (poson), Quality (poion), Relation (pros ti), Place (pou), Time (pote), Position (keisthai), Possession (echein), Action (poiein), and Passion (paschein). Everything that can be predicated of the objects of cognition falls under one or other of these concepts, and for this reason Aristotle regards them as the most universal or highest generic notions, and describes them as the Categories of things. It is, however, only in the book "On the Categories" (Katêgoriai) that they are distinctly set forth to the number of ten. In other places Aristotle reduces the Categories to a smaller number. For example, in the Analyt. Post. I. 22, we find the ousia contrasted with the remaining Categories as with so many accidents, sumbebêkota (accidentia). And in Met. XIV. 2 only three are mentioned: ta men gar ousiai, ta de pathê, ta de pros ti (substances, attributes, relations).
13. From the Concept our thought proceeds to the Judgment. In a judgment we effect the union or the separation of two concepts by affirming or denying the one or the other (kataphasis and apophasis). It is in judgment that truth or falsity in our knowledge first appears; we can predicate neither truth nor falsity of the unconnected concepts. The truth of our knowledge consists in the accord of our judgment with the objective order of things, in the fact that things are in objective reality as we judge them to be. The falsity of our knowledge consists in the contradiction between our judgment and the objective order, in our judging things to be what in reality they are not.
14. When a judgment has once been formed, another judgment may be derived from it -- this is the process of Inference. From judgment, then, we proceed to inference. Inference is defined by Aristotle (Top. I. 1) as logos en ho tethentôn tinôn heteron ti tôn keimenôn ex anagkês sumbainei dia ton keimenôn -- a discourse in which from certain premises, and by means of these premises, something different from the premises necessarily follows. We must, however, distinguish between Syllogistic and Inductive Inference.
(a) The Syllogism draws a particular conclusion from an universal major premise by means of a third proposition (minor premise), evolving in this process a proposition which was already virtually contained in the universal. In other words, by means of the Middle Term it connects the Major Term as predicate, with the Minor as subject. In his teaching regarding the syllogism, Aristotle has in view only the categorical syllogism. He distinguishes three syllogistic Figures (schêmata) according as the Middle Term (horos mesos) is subject in one premise and predicate in the other, or as it is predicate in both premises, or as it is subject in both premises. (The Fourth Figure was introduced at a much later period.)
(b) Inductive inference, on the other hand, follows an opposite direction; it proceeds from particular to general propositions; it concludes from the fact that a certain concept belongs to all those members of a class of which we have experience that it belongs to the entire class, and is an essential attribute of the class. In other words, Induction (epagôgê, ho epagôgês, sullagismos) concludes "that a concept of greater extension is predicate of a concept of smaller extension, from the fact that it is predicated of several or of all of the objects included under the latter." (Anal. Prior. III. 23.)
(c) The syllogism is, of its nature, antecedent to the Inductive process, for it proceeds from that which is first in order of nature (the Universal) to that which is subsequent in nature (the particular). But for us the Inductive Inference comes first, since it proceeds from what is first in our experience (the individual) to that which we attain to subsequently (the universal). In itself the syllogism is a more rigorous and a clearer form of inference; for us Induction is the form more immediately within reach, and it is therefore the clearer and more convincing.
15. The syllogism, in its turn, is the means of Proof. Proof consists in the demonstration of the truth of one proposition from the truth of another; and as this can be effected only by deducing the one from the other, it follows that Proof is not possible without this syllogism. The syllogism, regarded as the means of Proof, is of different kinds:
(a) The Apodictical (Demonstrative) Syllogism, when our conclusion is drawn from true, certain, and indisputable premises.
(b) The Dialectical Syllogism, which draws its conclusion from merely probable premises, ex endoxon; ex probabilibus.
(c) The Eristic Syllogism draws its conclusion from premises which have only an alleged or apparent probability (ek phainomenôn endoxôn). (Top. I. 1.){2}
16. Proof, as obtained by the syllogism, cannot be carried back indefinitely. It must ultimately arrive at the undemonstrable, and here come to an end. For if proof were to continue indefinitely, it could never be completed -- the endless can never be traversed -- and we should thus have no proof at all. In such a supposition proof would become wholly an impossibility. The undemonstrable, which fixes the limit of the process of proof, must, therefore, consist of certain propositions which do not admit of proof, and which, moreover, do not need it, their truth being self-evident to the intellect. These propositions are, in the first place, the truths of Immediate Experience; and, in the second, the First Principles of Reason (archai). Without these no proof is possible, they are the basis of all demonstration.
17. The First Principles of Reason belong to the nous. The mind arrives immediately at the knowledge of them on comparing together the highest or most general concepts, which it obtains by the process of abstraction, from the individual objects presented to it. They differ in kind, just as the ultimate concepts from which they are formed differ in kind. The highest of these principles is the Principle of Contradiction: to auto hama huparchein te kai me huparchein adunaton to auto kai kata to auto (Met. IV. 3): at the same time, and under the same respect, a thing cannot at once be and not be. Next in order comes the principle of Excluded Middle. These principles are not only the first or highest in the order of thought, they are also the highest in the order of Real Being. Thought follows Being, and what is first in order of thought must be first also in the order of Being. These principles, then, control not only the whole domain of Logic, but also the whole domain of Metaphysics.
18. The syllogism being the means of proof is also the instrument or operative element in science. Knowledge is acquaintance with the causes from which phenomena necessarily result; we have knowledge of an object only when we understand why it is thus, and not otherwise. It is the task of science to penetrate to the ultimate causes and reasons of phenomena, to deduce and explain phenomena from these causes. This task can be accomplished only by the use of the rational syllogism, which reasons from the result to the cause, or from the cause to the result. The syllogism is, therefore, the indispensable instrument of science. Hence three important consequences: --
(a) In the first place, science, considered in its subjective aspect, holds a middle place between immediate experience and the first principles of Reason -- these being the opposite extremes in human knowledge. Neither mere experience, nor a knowledge of first principles, can be called science. Scientific knowledge is intermediary between both, it is established by the rational syllogism, on the basis furnished, to which Experience and the principles of Reason alike contribute.
(b) Scientific knowledge, properly so called, is attainable only in the case of those phenomena which are of constant, or at least usual occurrence, not in the case of those which appear only occasionally or accidentally; for the former permit us to argue the existence of a cause uniformly effective; the latter warrant no such conclusion.
(c) Lastly, since the truths reached by the scientific syllogism are necessary truths, it follows that not only has science to deal with the unchangeable and necessary elements of things, but further that its aim is to obtain knowledge of that which is necessary. Hence the general maxim: Scientia est de necessariis.
19. We may sum up our exposition of this part of Aristotle's philosophy in the words of the philosopher himself (Anal. post. I. 18): There are two means to intellectual knowledge -- Induction, or rather the abstraction obtained through Induction, and the rational Syllogism. Everything that we know scientifically we know by the one means or by the other. Induction -- which enables us to reach general notions by a process of abstraction -- conducts us immediately to the concepts of widest universality, and mediately to the First Principles which result from comparing these concepts together The rational Syllogism, on the other hand, adopting as its basis both Experience and the First Principles of Reason, conducts us to the causes of phenomena, and aiding us to reach the ultimate and highest causes of all Being, lifts us at last to Philosophy -- the crown of intellectual knowledge, the queen of all the sciences.
{1} It is clear that Aristotle understands by morphê or eidos when he uses the term to signify constituent principles of individual objects, not the outward form or species of the individual which manifests itself to the senses, but the inner form or species which the intellect alone can perceive. Aristotle is, however, careful to make his meaning unmistakable, for when he uses eidos and morphê in the sense of their inner forms or species, he adds the epithet "Kata logon."
{2} The Sophistical Syllogism is a fallacy, a conclusion obtained from false premises, or by means of an illegitimate combination of the members cf. the syllogism.