THE PHILOSOPHY OF DESCARTES Methodology.—Like Bacon, his older contemporary, and Spinoza, his younger contemporary, Descartes was deeply inter ested in the problem of method—the determination of the right method for obtaining real knowledge by the natural light of rea son. Like numerous thinkers before him Descartes was thoroughly dissatisfied with the method of scholasticism then still in vogue.
The scholastic method, on which Descartes had been nurtured at La Fleche, consisted mainly in attempting to solve problems by citing the views of more or less eminent writers or "authorities," instead of dealing with the problems themselves. It called for much book-learning, as well as much ingenuity in reconciling or harmonizing conflicting authorities, but it did not encourage in dependent research or thought. Now Descartes was not a book worm by nature, and his early acquired habit of spending much time in bed was also more conducive to thinking than to much reading. Moreover, his genius was essentially mathematical; and in mathematics the question of "authority" did not arise even at his Jesuit school, where it counted in most other studies. Ac cordingly, we find Descartes engaged in questions of method al ready at an early stage in his career, and returning to them again and again subsequently. They are dealt with in his unfinished Rules for the Direction of the Mind (1628), in his fragmentary dialogue The Search after Truth (probably written either in 1628 or in 1641), in his Discourse on the Method of Rightly Con ducting the Reason (published in 1637), in his Meditations on First Philosophy (published in 1641), and in The Principles of Philosophy (published in 2644).
In his autobiographical Discourse, Descartes relates how his dissatisfaction with book-learning came upon him. "I have been nourished on letters since my childhood, and since I was given to believe that by their means a clear and certain knowledge could be obtained of all that is useful in life, I had an extreme desire to acquire instruction. But so soon as I had achieved the entire course of study, at the close of which one is usually received into the ranks of the learned, I entirely changed my opinion. For I found myself embarrassed with so many doubts and errors that it seemed to me that the effort to instruct myself had no effect other than the increasing discovery of my own ignorance. And yet I was studying at one of the most celebrated schools in Europe. . . . I learned there all that others learned . . . and I did not feel that I was esteemed inferior to my fellow-students. . . . And this made me take the liberty of judging all others by myself and of coming to the conclusion that there was no learn ing in the world such as I was formerly led to believe it to be." And in his Rules he promptly demands that the investigation of any problem should not be dominated by what others have thought about, but by what we ourselves can see clearly or infer with certainty. "For" (he explains) "we shall not, for instance, become mathematicians, even if we know by heart all the proofs that others have elaborated, unless we have an intellectual talent that fits us to resolve difficulties of that kind. Neither, though we have mastered all the arguments of Plato and Aristotle, if we have not the capacity for forming a solid judgment on these mat ters, shall we become philosophers." The one study which gave him real satisfaction was mathe matics, "because of the certainty of its demonstrations and the evidence of its reasoning." He felt that there must be something about mathematics which made it a model for other studies. And he recalled with some satisfaction that "the earliest pioneers of philosophy in bygone ages refused to admit to the study of wisdom anyone who was not versed in mathematics, evidently believing that this was the easiest and most indispensable mental exercise and preparation for laying hold of other more important sciences." Now Descartes did not exaggerate the importance of mathematics after the manner of Pythagoras, as did even some of the most eminent astronomers of the 16th and 17th centuries. On the con trary, he speaks rather contemptuously of pure mathematics as such, remarking that "there is nothing more futile than to busy one's self with bare numbers and imaginary figures in such a way as to appear to rest content with such trifles." It was only the method of mathematics that appealed to him. And gradually the conviction grew on him that the method of mathematics could be extended to other sciences. Reference has already been made above to his experience on Nov. Io, 1619, for which he went on a pilgrimage to our Lady of Loretto. In course of time he formed the idea of "a species of mathematics," or a kind of "universal mathematics," that shall be applicable to all kinds of investiga tions. What he was thinking of was what may be called a Meth odology, or a study of scientific method, calling it a "species of mathematics" simply because "mathematics" literally means science. Methodical procedure in research was regarded by Des cartes as of first-rate importance. Random search for knowledge and trust in some chance luck he condemned as at once fruitless and intellectually demoralizing.
Now the method of mathematics consists in beginning with the simplest notions and then proceeding cautiously to deduce infer ences from them. Similarly in all scientific investigations one should begin with the simplest and surest notions, and advance logically to more complex truths by a progressive synthesis of the simpler factors ; that is, by deduction. Descartes realized, of course, that knowledge is derived from experience as well as from deduction. But, in striking contrast with Bacon (whose Novum Organism he praised and commended to those who wished to fol low the empirical path), he put more faith in deduction than in experience. Experience begins with very complex objects, and so our inferences from it are frequently fallacious, whereas deduc tion, according to Descartes, cannot be erroneous if carried out with moderate understanding. "This" (he says) "furnishes us with an evident explanation of the great superiority in certitude of arithmetic and geometry to other sciences. The former alone deal with an object so pure and uncomplicated, that they need make no assumptions at all which experience renders uncertain, but wholly consist in the rational deduction of consequences." The moral he draws is that "in our search for the direct road towards truth, we should busy ourselves with no object about which we cannot attain a certitude equal to that of the demon strations of arithmetic and geometry." The first problem of method turns on the starting-point, the simple notions or principles which furnish the material for the subsequent deduction. If the initial premises are false even the soundest deduction cannot lead to knowledge. How then do we come by our simplest notions or principles? "The first principles," says Descartes, "are given by intuition alone." And by intuition he means "the undoubting conception of an unclouded and atten tive mind, which springs from the light of reason." Such intui tions are not uncommon. "Thus each individual can have intui tion of the fact that he exists, and that he thinks; that a triangle is bounded by three lines only; a sphere by a single superficies, and so on. Facts of such a kind are far more numerous than many people think who disdain to direct their attention to such simple matters." Intuition and deduction, then, "are the most certain routes to knowledge." If any complex problem presents itself, the proper course is to analyse it into its simplest elements or notions, enumerate these carefully (this enumeration Descartes calls induction), make sure of each of them by intuition, and reason from them by deduction.
In the Rules Descartes made no attempt to get behind intuition as described and exemplified above. The Discourse on Method, however, is much more sophisticated. It begins with a methodical doubt which is intended to serve as a severe test for whatever may claim to serve as the sure starting-point of knowledge. Everything must be questioned (de omnibus dubitandum) so that we may discover something that is beyond doubt. At first every thing seems to succumb to it—traditional beliefs, commonly accepted ideas, the very facts of direct observation may all be but illusions and dreams. Eventually, however, something is dis covered that is beyond cavil; namely, doubt itself. He who doubts cannot doubt the reality of his doubting. But what is doubt? It is an act of thinking. And thinking implies a thinker. And so, says Descartes triumphantly, Cogito, ergo sum—"I think, there fore, I am." This, then, is an ultimate certainty. But why is it accepted as certain? Because it is so clearly and distinctly real ized—it is an ultimate intuition that cannot be denied. This, however, implies that whatever is apprehended as clearly and dis tinctly is true. In this way Descartes found a philosophical basis for the acceptance of intuitions; and deduction from intuitions must at each step be as clearly and distinctly apprehended as the initial intuitions, though the connection between the final stage of a series of deductions and the initial intuitions may be a mat ter of memory rather than of immediate apprehension. Among the ultimate intuitions Descartes evidently included the principle of universal causation, otherwise he could never have passed from Cogito, ergo sum to the existence of God, and from the existence of God to the reality of things that are clearly and distinctly ap prehended. But these questions pertain to his metaphysics.
Metaphysics.—Descartes once compared himself to Archi medes. This Greek founder of mechanics had said that if he could only find a fixed point in space to serve as a fulcrum for a suitable lever, he could lift the whole earth. Similarly, Descartes, in his stage of methodical doubt, said that if he could only dis cover something indubitable he would rear on it a whole system of real science. And, as was explained above, Descartes f ound the required bedrock in the activity of doubt itself, in thought Cogito, ergo sum. By "thought" he meant not only what is com monly meant by that term (the reflective solution of difficulties), but almost every kind of mental experience. "By the word thought I understand all that of which we are conscious as operating in us. And that is why not only understanding, willing, imagining, but also feeling are here the same thing as thought." But, even if we substitute the term "consciousness" for Descartes' "thought," what exactly is the extent of the knowledge furnished by the certainty that "I think"? It seems to be extremely limited, and to amount to no more than "I think" or "I am a thinking (or conscious) being," or "I experience certain mental processes or ideas." It does not warrant the reality of the apparently material objects of our perceptions ; it does not prove the reality even of the body of the thinker. For in dreams such experiences occur although admittedly there are no such material objects corre sponding to them. And, adds Descartes, "the same thing, perhaps, might occur if I had not a body at all." If so, thought might be a purely subjective matter, and throw no light at all on the ques tion of the reality of an external world. There would be little comfort in the certainty that "I think, therefore I am" if the world of which I am conscious is but my dream-world, and "I" am but a solitary dreamer. It seems evident that Descartes' line of thought might end in so-called subjective idealism, or even in solipsism. It would be no great exaggeration to say that modern idealism and solipsism are the direct offspring of Descartes' thought. This, no doubt, may be regarded as a measure of his influence on modern philosophy; it may also be regarded as a measure of the mischief which he has wrought. Descartes did not consider sufficiently the claims of our waking consciousness to a direct apprehension of real external objects; his argument about dreams is not convincing, for, after all, it is easy enough to distin guish between dreaming and waking consciousness, and people are sometimes mistaken about what they think that they really think. He was probably betrayed partly by a bias common among mathe maticians from the days of Pythagoras and Plato onwards, and partly by the early Christian tendency (under Platonic and Neo Platonic influence) to belittle the material world. The former was probably the more important influence. Mathematicians as a class are so preoccupied with ideal or mental constructions that they are apt to exaggerate the powers of pure thought. Descartes clearly betrays this tendency already at the very beginning of his Rules for the Direction of the Mind, where he speaks of knowl edge as though it were a kind of illumination which streams forth from the mind in the same way, without regard to differences in the objects studied. "The sciences," he says, "are identical with human wisdom, which always remains one and the same, however applied to different subjects, and suffers no more differentiation proceeding from them than the light of the sun experiences from the variety of the things which it illumines." Descartes himself, however, was not a solipsist or even an ideal ist ; his religion and his science saved him from that. He had, therefore, to bridge the gulf between the mere cogito and the ex ternal world. This he endeavoured to do by making his "I think, therefore I am" an argument for the existence of God, and then making God's being the ground for his belief in the existence of an external world. Descartes offers three proofs for the existence of God, one of them is a priori, based on the implication of the very notion of God, the others are a posteriori and argue from effect to cause. The a priori, or ontological proof, adapted more or less from St. Anselm, and most in accordance with Descartes' mathematical method, runs as follows: "When the mind con siders the diverse conceptions which it has, it discovers the idea of a Being who is omniscient, omnipotent and absolutely perfect, which is far the most important of all ; and in this idea it recog nizes not merely a possible and contingent existence, as in all the other ideas it has of things which it clearly perceives, but one which is absolutely necessary and eternal. For just as when it perceives that it is necessarily involved in the idea of a triangle that it should have three angles equal to two right angles, it is absolutely persuaded that a triangle really has three angles equal to two right angles, so from the fact it perceives that necessary and eternal existence is comprised in the idea of an absolutely perfect Being, it must clearly conclude that this absolutely per fect Being exists." Of the a posteriori proofs the more important one is the so-called anthropological one based, not on the mere implication of the concept God, but on the existence of the idea in an existing but imperfect mind or minds. Descartes formulates it as follows. "As we find in ourselves the idea of a God, or a supremely perfect Being, we can investigate the cause which pro duces this idea in us. But considering the immensity of the per fection it possesses, we are constrained to admit that it can only emanate from an all-perfect Being, that is, from God who really exists. For it is not only made manifest by the natural light that nothing cannot be the cause of anything whatever, and that the more perfect cannot proceed from the less perfect as its efficient and total cause, but also that it is impossible for us to have any idea of anything whatever, if there is not within us or outside us an original which actually possesses all the perfections. But as we do not in any way possess all these absolute perfections of which we have the idea, we must conclude that they reside in some other nature different from ours, that is, in God." The other a posteriori argument infers the existence of God from the think er's own existence, and his continued existence. These imply a Creator who has not only created the thinker, but maintains him in existence. For existence at one moment is itself no reason for existence at a subsequent moment, so that the conservation of whatever exists is really a continued creation.
The combined effect of all these arguments, taken in conjunc tion with his doctrine of innate ideas, of which the idea of God is one, may have been to give Descartes the conviction that he had in some way a direct intuition of God revealing Himself to Des cartes through his innate idea of Him. But Descartes does not make himself clear on this point.
Having proved the existence of God as the supremely perfect Being, Descartes argues in the next place that God would not deceive the thinking beings He has created. So our sense-percep tions cannot be mere illusions, and there must exist an external world of Beings which we apprehend in perception. In this way, whereas his predecessors were wont to prove the existence of God from the existence of the world, Descartes inferred the existence of the world from the existence of God. But now he seems to have proved too much. Undoubtedly there are such experiences as illusions and errors. How shall we distinguish the real from the illusory? Descartes meets the difficulty by reverting to one of the main points in his methodology—we can only be sure of what we apprehend clearly and distinctly. Error is the result of the neglect of this precaution. It arises when our will goes beyond our under standing, as it often does. For our will has no limits, whereas our understanding is severely limited. And judgment, according to Descartes, is a decision of the will.
Clear and distinct apprehension must also be our guide in deter mining what these external material things essentially are. The sense-qualities, the so-called secondary qualities of things, such as colour, smell, etc., are not clearly and distinctly thinkable. Extension in three dimensions, and motion are the only features of material bodies that are clear and distinct to thought, and so they alone are the real essential features of material things, the so-called secondary qualities being but the subjective experiences of the percipient. In this way Descartes helped to lay the founda tions of a mechanical interpretation of physical Nature. On the other hand the essential feature of minds is thought or conscious ness. Minds are essentially thinking substances, just as bodies are essentially extended substances. For Descartes, accordingly, Reality consists of God, the perfect Being and Creator, and His Creations, namely, thinking substances, or minds, and extended substances, or bodies. And, prompted by his religious training, Descartes endeavours to set bodies and minds in extreme opposi tion to one another—whatever mind is, body is not. One result of this is that because mind is active, body is not, and so he con ceives of motion, not as a property of bodies, but as something put into them by God. Another result is that there can be no inter connection between body and soul. Lower animals are conse quently conceived by Descartes as mere automata, cleverly con structed mechanisms without soul. And the undeniable conjunc tion and apparent interaction of mind and body in human beings is in the last resort explained by the constant intervention of God.
The philosophy of Descartes has undoubtedly exercised a potent influence on modern thought, and to that extent the usual desig nation of Descartes as the father of modern philosophy is justified. But the intrinsic merits of his philosophy have been grossly exag gerated; and the exaggeration is itself due to a misinterpretation of Descartes' mentality. Descartes was a dual personality. Two tendencies struggled within him. On the one hand, there was the mathematical genius with a passion for clear and distinct ideas, and for logical deduction. On the other hand, there was the loyal Catholic, genuinely attached to a certain traditional theology. So long as he pursued problems of a purely scientific character, especially problems pertaining to pure or applied mathematics, he was in his element and showed his master mind. But the moment he attacked problems of general philosophic orientation, he was the traditional theologian rather than the revolutionary philosopher. Historians of philosophy have tried to save the philosophic reputation of Descartes by treating his theology as mere camouflage. But that is a mistake. Mersenne had a keen scent for heresy, yet he defended Descartes' orthodoxy; and Mersenne was well informed about Descartes. It is not very un usual even in the nth century, it was certainly not unusual in the i 7 th century, for the same person to be a detached scientist when dealing with one set of problems, and a conservative theologian when dealing with another set of problems. And Descartes was of that type. In the same breath with which he asserted that the mind should admit no other methods than intuition and deduction, he also asserted "but this does not prevent us from believing mat ters that have been divinely revealed as being more certain than our surest knowledge, since belief in these things . . . is an act, not of our intelligence, but of our will." His abandonment of the idea of the earth's motion and his substitution of the vortex theory was probably due to his genuine regard for the authority of the Catholic Church, not to fear. Saumaise, who visited Des cartes at Leyden in 1637, reports that he was a Catholic "des plus zeles." His whole orientation was essentially that of popular Christian theology, with its supernatural God, who created souls and bodies. And when he went the length of regarding distinctions between good and evil, between truth and falsehood as depending on the arbitrary decisions of the Divine Will, he really abandoned altogether the realm of rational philosophy for that of a particu larly narrow mediaeval theology. Descartes' methodical doubt has misled people into supposing that he was a revolutionary philosopher. But in the history of human thought real "believers" have posed as sceptics almost as often as real sceptics have posed as believers.