Jacques Maritain Center : The First Principles of Knowledge

Chapter IX.
Cartesian Doubt.


  1. The methodic doubt of Descartes as distinguished from mere scepticism.
  2. The plausible part of Descartes.
  3. Passages in his works whence to gather the substance of his method.
  4. The destructive part of his work.
  5. It falls into the principles of universal scepticism, and makes the future work of construction logically impossible.
  6. The constructive part itself.
  7. General estimate of Descartes.


I. THE doubters with whom we have just been dealing make doubt their final goal, they doubt and rest there: but we have now to deal with a universal doubt which is supposed to be a means of helping on the mind towards well-assured knowledge. Hence it is called methodic doubt, as Being only a way, or rather part of a way, to an end, not an end in itself. Descartes who, it should be remembered, gives warning that his system is dangerous for all but the few, is the deviser of this method of doubt, which has won for him more credit with some people than close investigation of its merits will bear out. The fact is, Descartes says many things that are either quite true, or contain an obvious element of truth; and, in his replies to objections, he may seem to get over certain difficulties which, if reference were made back to his system, would be found to be insuperable. But of course few readers, go to the trouble of making such reference, and so, the author is the gainer. Even a well-informed writer like Hamilton{1}, speaks of the error of Descartes as accidental rather than substantial; whereas his error is substantial and the admixture of truth incidental. There are other critics who, to less attentive readers, may appear to approve, in the main, of Descartes, yet who, if read more carefully, will be found to disagree with him fundamentally. Instances are Balmez, Sanseverino, and Tongiorgi. However, our business is much more to refute the popular version of Cartesianism, than to score a victory over one long since dead and beyond the reach of our weapons; so that to us it is a matter of small consequence, whether a wide collation of passages might not do something to mitigate the crudeness of the system, when taken in outline.

2. What the snatch-and-away class of readers would seize upon in Descartes is just what is most plausible and insidious. The surface of his doctrine looks fair, and the prominent parts are easily grasped. He finds that his mind is like a basket containing apples, good and bad: and he proposes to empty the whole out, and put back only the good. Certainly a very natural thing to do, if the mind is a basket of apples. But so patently is the mind not a basket of apples, that a directly opposite course of, action has suggested itself to others. Thus Cardinal Newman has declarations to the effect that, if he were driven to choose between the two extreme alternatives, be would rather begin by holding all present beliefs, and gradually letting go the untenable, than start with the clean sweep made by universal doubt. And this process Wundt actually recommends, so far as he teaches, that instead of beginning from the idealist point of view, men should first hold their ideas to be real: then they should eliminate what can be shown to be merely subjective, and keep the residue as objective. Thus the analogy of the basket is catching indeed to an average reader; but catching in the way of that now forbidden article, the man-trap.

3. In three different places of his works, Descartes describes the successive steps of his system; yet to inquire what precisely this system is, seems hardly to enter seriously into the minds of ordinary retailers of philosophic opinions. Perhaps they are secretly led by the principle which we have seen Mr. Pollock avow, namely, that "systems" are nothing, but a few "vital ideas" everything. With regard to Descartes, any one who will carefully compare his threefold account of his system, will be quite convinced that the author had not steadily made up his mind how the several steps in the progress were to succeed each other. The Discourse on Method, Part IV., the Meditations, especially the first, and the Principia (Part I. in initio), would not quietly fuse together into a Summa, though they are meant to be three descriptions of one leading process. However, in the destructive part of this process, Desca es is pretty uniform: and it is this part chiefly which we must assail, destroying the destroyer.

4.The philosopher soliloquises somewhat in this strain: I, being now in the maturity of my faculties, find that the formation of my opinions has hitherto been not at all critically conducted; and whereas it would be endless to test each of my beliefs separately, therefore I must aim at some comprehensive method. Recurring to my reasons for dissatisfaction, I find that my senses have often deceived me, and therefore as means of knowledge they are to be suspected: which suspicion is immediately extended to the rest of my knowledge, so far as it has its beginning in the senses. But my intellect itself is open to direct assault: it too has been deceived in matters when I felt quite sure, and I can doubt even about mathematical truths, which are considered as types of clearness. Next as to grounds of misgiving which are extrinsic to my own faculties, sensitive and intellectual; whence have I these faculties? I am told that I have them from an Omnipotent Creator: and if He is Omnipotent, He can do all things, and consequently He can make me essentially a creature of delusions. Or suppose I am the work of a maker less than omnipotent; then all the more likely is the less powerful maker to have made me ill. But perhaps this is irreverent: so let us suppose it is some spirit that is perpetually turning me to mockery. Thus on all sides I find my very faculties untrustworthy, and trying to doubt, I can doubt the existence of my body and its senses, of earth and heaven: "and finally I am driven to admit that there is nothing of what I previously believed which I cannot in some way doubt: and this not lightly and inconsiderately, but because of very strong and well-weighed reasons."

It is not extravagant to hope the reader will allow, that the way to criticize the above "method" is not simply to look out for some stray "vital ideas" which it may contain, but to look to the whole method of which a part has just been sketched, and ask, can the proposed whole admit of that part. Descartes is not arguing in behalf of permanent doubt: else he would be one of the dogmatic sceptics refuted in the last chapter: he is arguing for doubt as a preliminary to certitude, and this fact is vital to his system, whatever may be the "vitality of ideas" out of systematic connexion with each other. Now as a system Descartes' method fails, if his principles of destruction are inconsistent with any subsequently applied principles of reconstruction. He first doubts in order afterwards to be certain: he does not indeed try to draw certitude out of doubt itself; but he does try to start from a state of doubt on the way to certitude. Hume{2} and Reid agree that he has so buried himself beneath the ruins of the edifice he has pulled down, that rebuilding is beyond the power of the utterly crushed enterpriser.

5. If it were necessary, for purposes of refuting his "method," to follow Descartes into all the details of his arguments, we should require at once to enter upon such special subjects as the trustworthiness of the senses, the nature of mathematical truths, the nature of necessary truth, the regulation of Divine omnipotence by Divine wisdom and goodness, the permission of evil, the powers of wicked spirits in face of a Provident Ruler, and other large questions. But there is a shorter way: Descartes, falls into the inconsistencies of the universal sceptics, and is logically forced to abide with those in whose company he is unwilling to remain. He professes to be able, "seriously and for well-weighed reasons," to doubt the validity of his faculties, and truths which present themselves to his mind with the force of evidence. Out of such doubt there is no rescue. A man so circumstanced has no right even to his "I think, therefore I exist" (Cogito, ergo sum); and if he says that on this point doubt is impossible, he says so only by revoking what he had said before; for if his whole nature may be radically delusive, it may be delusive here. He says the doubter cannot doubt his own existence: but neither can the doubter doubt consistently the validity of his own faculties and of evident propositions. Some have so bemuddled themselves that they have felt alarmed as to their own existence; and a large system of pantheism denies the reality of the separate Ego. If this bemuddlement is a degree worse than that of Descartes, the question is only one of degree, not of kind. It is substantially the same kind of evidence which testifies that I exist, and that what I know, I know, or that my faculties are veracious. A man may and must start from ignorance, and by the experience of his intellectual life first discover, empirically, that he is an intelligent being: also a man may gradually test by experience that he is waking up from a dream or from a delirium. But no man, from the position of what Descartes styles the proved suspiciousness of his very power of knowing anything, can coolly go on to use his suspected faculties as witnesses in their own behalf, when they say Cogito, ergo sum. The only irrefragability of Descartes, at this point, is the convincing evidence of his maxim on other principles than the Cartesian, not on Cartesian principles.

There is, however, one point stated in the last paragraph which ought not to be left without further notice; and it is that some defence may apparently be made for Descartes, inasmuch as he places the certainty of self above the certainty of ordinary truths which are immediately evident. A large number of philosophers have remarked that our own states of consciousness, and a knowledge of some kind of self, are matters beyond all question: whereas at least a question may be raised as to whether our thoughts in general stand for any objects beyond themselves. The absolute unquestionableness on the one side, and the possible questionableness on the other, seem at first sight to rest on a well-grounded distinction: but closer inspection will not bear out first impressions. For if we push scepticism concerning truths other than the truth of our consciously modified self to their logical conclusions, we shall find ourselves reduced to the inability of making any certain declaration whatever. We shall be as ill off as Mill{3} when he admitted the necessity of deductions from axiomatic truths, but denied the necessity of the axioms: as though the evidence for one were not as compelling.as the evidence for the other, and as though reasoning could have a prerogative over immediate intuition. If Hume{4} is any support, we have him as an ally in the present instance; for he denies to Descartes that there is "any original principle which has a prerogative over others," such as the Cogito ergo sum is asserted to have. Allow Descartes' principles to the full, and instead of your fixed certainty that you, the doubter, exist, you will find yourself muttering some verses of Byron, which one sees occasionally quoted:

So little do we know what we're about in
This world, that I doubt if doubt itself be doubting.
O doubt, if thou be'st doubt, for which some take thee,
But which I doubt extremely, &c.

These expressions are wild utterances, but Descartes has no right to complain of them, and he ought to have realized the startling fact.

Yet so easily do certain minds isolate "vital ideas," that some speak as though the whole onslaught against Descartes was because he stood up vigorously for the fact of self-existence, as revealed in thought and as a primary cognition! We all, stand up in defence of that piece of knowledge; our quarrel is with the previous scepticism. We would wipe out from Descartes' system other things besides, but first of all, that which most strongly characterizes it, its initial stage of universal doubt; ignoring which the "good easy reader" of reports at second hand, seems to be under the delusion, that Descartes merely said we had reasons for dissatisfaction with our early way of laying up mental stock, and that the stock in hand should, in mature years, be thoroughly overhauled. Descartes teaches a great deal more than that: he claims to have proved, by reasons, that mathematical evidence may be fallacious, and that so may be our very inmost nature. Do not overlook this essential part of the system, if you would be anything like a competent critic: and do not fail to notice how such a beginning is absolutely fatal to further progress.

On the principles involved in his "methodic doubt" alone, Descartes would find defence impossible; but he labours under the further disadvantage, that there are principles, in other parts of his philosophy, which serve to cripple him very much, and render it still more difficult for him ever to recover his certitudes. Truth, according to Descartes,{5} rests ultimately on the Divine free-will: and had God so chosen, our necessary truths might have been the reverse of what they are. This is a very different thing from saying, that God could have given to us, or to other beings having our place, a palate which enjoyed oil of vitriol, and a stomach which could digest aconite; in all which assertions there is no clear contradiction. But to assert that God could have reversed, not merely physical arrangements, but also metaphysical principles, is to strike at the root of all truth and of all knowledge, and to annihilate the difference between truth and falsehood. Truth is no longer a sacred thing; and that God should use His omnipotence to deceive us, no longer admits of disproof. In fact nothing admits of proof or disproof, for that which both aim at ceases to have a meaning.

6. As to the constructive part of the Cartesian system, we need only note its futility. In some accounts, next to his first great fact, Cogito ergo sum, he places a criterion of truth derived from the experience of this fundamental certitude. This last is accepted because it is contained in clear and distinct ideas: hence is derived the criterion: "That is true which is contained in clear and distinct ideas." But in other places Descartes pronounces the criterion, so obtained, to be invalid an invalidity which some might suppose him to limit to the external world until we have settled, that the faculty which has the clear and distinct ideas is from God, who cannot create lying powers of mind. Onward, therefore, to the proof of God's existence Descartes hastens: and argues in a circle, that God exists because our clear ideas affirm it, and our clear ideas validly make the affirmation because God is their voucher. Few who praise Descartes as the philosopher of "clear thought," care to look into his theory of "clear ideas:" and from that theory their own opinions. are utterly dissentient. Yet it is a fact that often a doctrine cannot be understood till its meaning is made to square with its context, and it is ridiculous to pretend to be in admiring agreement with an author, when really you and he are radically at disagreement, and when be does not decisively know his own mind. As a system Cartesianism is quite without supporters: and this is a fact -- a most important fact -- which a careful examination cannot fail to reveal to fancied adherents.

7. The general estimate of Descartes is by some put very high, by others much lower. Buckle, not a great authority on abstract sciences, is quite in the characteristic vein of the History of Civilization, when he calls Descartes "the Luther of Philosophy," who "believed, not only that the mind by its own effort could root out its most ancient opinions, but that it could, without fresh aid, build up a new and solid system. It is this extraordinary confidence in the power of the human intellect which gives this philosophy that sublimity which distinguishes it from all other systems." If Buckle had known more of what he was talking about, be would have been checked by the reflexion, that Descartes, in places where he brings forward his half- hearted theory of innate ideas, goes very near, at times, to denying the intellect's power of forming its own conceptions, and to declaring it wholly dependent upon infused ideas; that he takes away from us any natural means of passing from sensations to thoughts; that he makes all our certitude rest on the knowledge of God as the Author of life faculties, whilst this idea of God he makes necessarily dependent on a Divine communication.

The real position of Descartes seems to be, that he brought into prominence some useful doubts and some useful conceptions, which others carried to better issue than he did, and in this respect he not a little resembles Bacon; also that he started some dangerous ideas, which again others carried to worse issue than he did. It is of the latter that Bossuet, himself a sort of Cartesian, wrote: "To conceal nothing from you, I see that a tremendous conflict threatens the Church, under the name of Cartesian philosophy. I see that more than one heresy will spring from its principles, though, as I believe, from, their wrong interpretation."{6}

The mathematical services of Descartes were admittedly great, especially his share in the invention of analytical geometry; and in the physical sciences he is quite welcome to whatever honours his friends can vindicate for him; it is only his,"methodic doubt" that is here expressly condemned. Yet in regard to science as distinguished from philosophy, it may be noted that Whewell, in his History of the Inductive Sciences, lodges against him such charges as, that he misstated the third. law of motion; that he claimed to himself discoveries of Galileo and others, which cannot be allowed to one who "did not understand, or would not apply, the laws of motion which he had before him;" that "if we compare Descartes with Galileo, then of the mechanical truths which were easily obtainable in the beginning of the seventeenth century, Galileo took hold of as many, and Descartes of as few, as was possible for a man of genius;" that "in his physical speculations Descartes was often very presumptuous, though not more than half right," that he would not question nature, being ambitious of showing not simply what is, but what must be. These accusations may, or may not be justified, as far as we are concerned; our one great accusation is, that Descartes attempted the impossible, in trying to build up a system after giving positive reasons for the conclusion, that his faculties might be radically incompetent.


(1) As an additional example of the mischief which comes of not viewing Descartes' words in their context, and every philosopher's words in their context, it is instructive to observe how falsely St. Augustine has been quoted as a precursor of Descartes. St. Augustine does indeed use the very valid argument, that the existence of self is invincibly brought home to the conscious individual, and that it is asserted even in the act of doubting. But St. Augustine does not preface the argument by a suicidal declaration of scepticism, nor does he fall into the vicious circle of proving reason from God, and God from reason. Without first taking himself the fatal cathartic of universal doubt, but arguing against the possibility of universal doubt, he has passages like these: "If a man doubts, he lives; if he doubts that he doubts, he understands. If he doubts, it is because he wants to be certain. If he doubts, he thinks. If he doubts, he is conscious of his ignorance. If he doubts, he deems that he ought not to assent, save on reasonable grounds."{a} "You who wish for a knowledge of yourself, do you know your own existence? Yes, I do." "How do you know it?" "That I don't know." "Do you know whether you are simple or complex?" "No." "Do you know that you have the power of motion?" "No." Do you know that you are capable of thought ? " "Yes."{b} Finally, "Without any delusive phantasm of the imagination, I am certain that I am, that I know and love. As regards these truths, I have no fear of the arguments of the Academics who may object: but what if you are deceived? If I am deceived, I am." {c}

Not one of the quotations sanctions universal scepticism as a prelude to philosophic certainty.

(2) By the side of Descartes' theory it is interesting to place the view of Cousin,{d} that the possible forms of philosophy are four, sensism and idealism, each leading to scepticism, which in turn has for its reaction mysticism. He denies that scepticism can come first, being necessarily preceded by dogmatism, either sensistic or idealistic. "Negation is not the starting-point of the human mind, as it pre-supposes that there is something to be denied, hence something that has previously been affirmed. Affirmation is the first act of thought. Man, therefore, begins with belief, belief in this or that; and so the first system is dogmatic. Its dogmatism is either sensist, or idealistic according as the thinker trusts respectively thought or the experience of the senses. Mysticism marks the despair of the human mind, when after having naturally believed in itself, and started with dogmatism, it takes refuge from scepticism in pure contemplation, and the immediate intuition of God.

Such is the necessary sequence of systems of thought in the human mind."{e}

(3) Descartes is a warning against over-confidence in self for the working out of a new system. He complained that philosophy presented the appearance of a city built by many hands at different times; and he argued that a symmetrical whole required unity of workmanship. He tried himself to be the single workman, who should build up the whole of an enormous city, after first pulling down the old structures; but in both respects his efforts were failures, monumental failures for the warning of posterity. In a matter so open to human thought as the nature of its own certitude, no man of proper modesty should venture upon the boast; Heretofore the world has gone wrong, but at last ecce ego! Even the gentle Ferrier ventures to claim a few of these downright new discoveries; but they are, of course, all delusions: and of Comte, who cased to read other philosophers in order to develop his own thought, Mill says that he developed "a colossal self-conceit."

{1} Logic, Vol. IV. Lecture xxix. p. 91.

{2} Inquiry, Parti 1. sec. xii. in initio.

{3} Logic, Bk. II c. vi. §1.

{4} Inquiry, Parti 1. sec. xii. in initio.

{5} Meditations, Réponses aux Sixièmes Objections, n. 8.

{6} Pour ne vous rien dissimuler, je vois un grand combat se preparer contre l'église, sous le nom de philosophie Cartesienne; je vois naître de son sein, à mon avis mal entendu, plus d'une hérésie."

{a} "Si dubitat, vivit. Si dubitat, dubitare se intelligit. Si dubitat, certus esse vult. Si dubitat, cogitat. Si dubitat, scit se nescire. Si dubitat, judicat se non temere consentire oportere." (De Trinitate, 14.)

{b} "Tu, qui vis te nosse, scis esse te? Scio. Unde scis? Nescio. Simplicem te scis, an multiplicem? Nescio. Movere te scis? Nescio. Cogitare te scis? Scio." (Soliloq., Lib. II. cap. i.)

{c} "Sine ulla phantasiarum et phantasmatum imaginatione ludificatoria, mihi esse me, idque nosse et amare certissimum est. Nulla in his vereor. Academicorum argumenta formido, dicentium, quid si falleris? Si fallor sum." (De Civ., Lib. XI. c. 26.)

{d} Histoire de la Philosophie, Leçon 13me.

{e} "L'esprit humain ne débute pas par la négation; car, pour nier, il faut avoir quelque chose à nier, il aut avoir affirmé, et l'affirmation, c'est le premier acte de la pensée. L'homme commence donc par croire: il croit soit à ceci, soit à cela, et le premier système est le dogmatisme. Ce dogmatisme est sensualiste ou idéaliste, selon que l'homme se fie davantage ou à la pensée ou a la sensibilité. Le mysticisme, c'est le coup de désespoir de la raison humaine, qui après avoir cru naturellement à elle-même et débuté par le dogmatisme, effrayée par le scepticisme, se réfugie dans la pure contemplation et l'intuition immediate de Dieu. Tel est l'ordre nécessaire du développement des systèmes dans l'esprit humain." (Ib.)

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