René Descartes is a bold spirit who re-commenced the whole subject from the very beginning and constituted afresh the ground-work on which Philosophy is based, and to which, after a thousand years had passed, it once more returned. The extent of the influence which this man exercised upon his times and the culture of Philosophy generally, cannot be sufficiently expressed; it rests mainly in his setting aside all former presuppositions and beginning in a free, simple, and likewise popular way, with popular modes of thought and quite simple propositions, in his leading the content to thought and extension or Being, and so to speak setting up this before thought as its opposite. This simple thought appeared in the form of the determinate, clear understanding, and it cannot thus be called speculative thought or speculative reason. There are fixed determinations from which Descartes proceeds, but only of thought; this is the method of his time. What the French called exact science, science of the determinate understanding, made its appearance at this time. Philosophy and exact science were not yet separated, and it was only later on that this separation first took place.
To come to the life of Descartes—he was born in 1596, at La Haye in Touraine, of an ancient and noble race. He received an education of the usual kind in a Jesuit school, and made great progress; his disposition was lively and restless; he extended his insatiable zeal in all directions, pursued his researches into all systems and forms; his studies, in addition to ancient literature, embraced such subjects as philosophy, mathematics, chemistry, physics, and astronomy. But the studies of his youth in the Jesuit school, and those studies which he afterwards prosecuted with the same diligence and strenuous zeal, resulted in giving him a strong disinclination for learning derived from books; he quitted the school where he had been educated, and yet his eagerness for learning was only made the keener through this perplexity and unsatisfied yearning. He went as a young man of eighteen to Paris, and there lived in the great world. But as he here found no satisfaction, he soon left society and returned to his studies. He retired to a suburb of Paris and there occupied himself principally with mathematics, remaining quite concealed from all his former friends. At last, after the lapse of two years, he was discovered by them, drawn forth from his retirement, and again introduced to the great world. He now once more renounced the study of books and threw himself into the affairs of actual life. Thereafter he went to Holland and entered the military service; soon afterwards, in 1619, and in the first year of the Thirty Years’ War, he went as a volunteer with the Bavarian troops, and took part in several campaigns under Tilly. Many have found learning unsatisfying; Descartes became a soldier—not because he found in the sciences too little, but because they were too much, too high for him. Here in his winter quarters he studied diligently, and in Ulm, for instance, he made acquaintance with a citizen who was deeply versed in mathematics. He was able to carry out his studies even better in winter quarters at Neuberg on the Danube, where once more, and now most profoundly, the desire awoke in him to strike out a new departure in Philosophy and entirely reconstruct it; he solemnly promised the Mother of God to make a pilgrimage to Loretto if she would prosper him in this design, and if he should now at last come to himself and attain to peace. He was also in the battle at Prague in which Frederick the Elector-Palatine lost the Bohemian crown. Yet since the sight of these wild scenes could not satisfy him, he gave up military service in 1621. He made several other journeys through the rest of Germany, and then proceeded to Poland, Prussia, Switzerland, Italy and France. On account of its greater freedom he withdrew to Holland, in order there to pursue his projects; here he lived in peace from 1629 to 1644—a period in which he composed and issued most of his works, and also defended them against the manifold attacks from which they suffered, and which more especially proceeded from the clergy. Queen Christina of Sweden finally called him to her court at Stockholm, which was the rendezvous for all the most celebrated men of learning of the time, and there he died in 1650.[154]
As regards his philosophic works, those which contain his first principles have in particular something very popular about their method of presentation, which makes them highly to be recommended to those commencing the study of philosophy. Descartes sets to work in a quite simple and childlike manner, with a narration of his reflections as they came to him. Professor Cousin of Paris has brought out a new edition of Descartes in eleven octavo volumes; the greater part consists of letters on natural phenomena. Descartes gave a new impetus to mathematics as well as to philosophy. Several important methods were discovered by him, upon which the most brilliant results in higher mathematics were afterwards built. His method is even now an essential in mathematics, for Descartes is the inventor of analytic geometry, and consequently the first to point out the way in this field of science to modern mathematics. He likewise cultivated physics, optics, and astronomy, and made the most important discoveries in these; we have not, however, to deal with such matters. The application of metaphysics to ecclesiastical affairs, investigations, etc., has likewise no special interest for us.
1. In Philosophy Descartes struck out quite original lines; with him the new epoch in Philosophy begins, whereby it was permitted to culture to grasp in the form of universality the principle of its higher spirit in thought, just as Boehme grasped it in sensuous perceptions and forms. Descartes started by saying that thought must necessarily commence from itself; all the philosophy which came before this, and specially what proceeded from the authority of the Church, was for ever after set aside. But since here thought has properly speaking grasped itself as abstract understanding only, in relation to which the more concrete content still stands over on the other side, the determinate conceptions were not yet deduced from the understanding, but taken up only empirically. In Descartes’ philosophy we have thus to distinguish what has, and what has not universal interest for us: the former is the process of his thoughts themselves, and the latter the mode in which these thoughts are presented and deduced. Yet we must not consider the process as a method of consistent proof; it is indeed a deep and inward progress, but it comes to us in an ingenuous and naïve form. In order to do justice to Descartes’ thoughts it is necessary for us to be assured of the necessity for his appearance; the spirit of his philosophy is simply knowledge as the unity of Thought and Being. And yet on the whole there is little to say about his philosophy.
a. Descartes expresses the fact that we must begin from thought as such alone, by saying that we must doubt everything (De omnibus dubitandum est); and that is an absolute beginning. He thus makes the abolition of all determinations the first condition of Philosophy. This first proposition has not, however, the same signification as Scepticism, which sets before it no other aim than doubt itself, and requires that we should remain in this indecision of mind, an indecision wherein mind finds its freedom. It rather signifies that we should renounce all prepossessions—that is, all hypotheses which are accepted as true in their immediacy—and commence from thought, so that from it we should in the first place attain to some fixed and settled basis, and make a true beginning. In Scepticism this is not the case, for with the sceptics doubt is the end at which they rest.[155] But the doubting of Descartes, his making no hypotheses, because nothing is fixed or secure, does not occur in the interests of freedom as such, in order that nothing should have value except freedom itself, and nothing exist in the quality of an external objective. To him everything is unstable indeed, in so far as the Ego can abstract from it or can think, for pure thought is abstraction from everything. But in consciousness the end is predominant, and it is to arrive at something fixed and objective—and not the moment of subjectivity, or the fact of being set forth, known and proved by me. Yet this last comes along with the other, for it is from the starting point of my thought that I would attain my object; the impulse of freedom is thus likewise fundamental.
In the propositions in which Descartes gives in his own way the ground of this great and most important principle, there is found a naïve and empirical system of reasoning. This is an example: “Because we were born as children, and formed all manner of judgments respecting sensuous things before we had the perfect use of our reason, we are through many preconceived ideas hindered from the knowledge of the truth. From these we appear not to be able to free ourselves in any other way but by once in our lives striving to doubt that respecting which we have the very slightest suspicion of an uncertainty. Indeed it is really desirable to hold as false everything in respect to which we have any doubt, so that we may find more clearly what is most certain and most knowable. Yet this doubt has to be limited to the contemplation of the truth, for in the conduct of our life we are compelled to choose the probable, since there the opportunity for action would often pass away before we could solve our doubts. But here, where we have only to deal with the search for truth, we may very reasonably doubt whether any thing sensuous and perceptible exists—in the first place because we find that the senses often deceive us and it is prudent not to trust in what has even once deceived us, and then because every day in dreaming we think we feel or see before ourselves innumerable things which never were, and to the doubter no signs are given by which he can safely distinguish sleeping from waking. We shall hereby likewise doubt everything else, even mathematical propositions, partly because we have seen that some err even in what we hold most certain, and ascribe value to what to us seems false, and partly because we have heard that a God exists who has created us, and who can do everything, so that He may have created us liable to err. But if we conceive ourselves not to derive our existence from God, but from some other source, perhaps from ourselves, we are all the more liable, in that we are thus imperfect, to err. But we have so far the experience of freedom within us that we can always refrain from what is not perfectly certain and well founded.”[156] The demand which rests at the basis of Descartes’ reasonings thus is that what is recognized as true should be able to maintain the position of having the thought therein at home with itself. The so-called immediate intuition and inward revelation, which in modern times is so highly regarded, has its place here. But because in the Cartesian form the principle of freedom as such is not brought into view, the grounds which are here advanced are for the most part popular.
b. Descartes sought something in itself certain and true, which should neither be only true like the object of faith without knowledge, nor the sensuous and also sceptical certainty which is without truth. The whole of Philosophy as it had been carried on up to this time was vitiated by the constant presupposition of something as true, and in some measure, as in the Neo-Platonic philosophy, by not giving the form of scientific knowledge to its matter, or by not separating its moments. But to Descartes nothing is true which does not possess an inward evidence in consciousness, or which reason does not recognize so clearly and conclusively that any doubt regarding it is absolutely impossible. “Because we thus reject or declare to be false everything regarding which we can have any doubt at all, it is easy for us to suppose that there is no God, no heaven, no body—but we cannot therefore say that we do not exist, who think this. For it is contradictory to say that what thinks does not exist. Hence the knowledge that ‘I think, therefore I am,’ is what we arrive at first of all, and it is the most certain fact that offers itself to everyone who follows after philosophy in an orderly fashion. This is the best way of becoming acquainted with the nature of spirit and its diversity from body. For if we inquire who we are who can set forth as untrue everything which is different from ourselves, we clearly see that no extension, figure, change of position, nor any such thing which can be ascribed to body, constitutes our nature, but only thought alone; which is thus known earlier and more certainly than any corporeal thing.”[157] ‘I’ has thus significance here as thought, and not as individuality of self-consciousness. The second proposition of the Cartesian philosophy is hence the immediate certainty of thought. Certainty is only knowledge as such in its pure form as self-relating, and this is thought; thus then the unwieldy understanding makes its way on to the necessity of thought.
Descartes begins, just as Fichte did later on, with the ‘I’ as indubitably certain; I know that something is presented in me. By this Philosophy is at one stroke transplanted to quite another field and to quite another standpoint, namely to the sphere of subjectivity. Presuppositions in religion are given up; proof alone is sought for, and not the absolute content which disappears before abstract infinite subjectivity. There is in Descartes likewise a seething desire to speak from strong feeling, from the ordinary sensuous point of view, just as Bruno and so many others, each in his own fashion, express as individualities their particular conceptions of the world. To consider the content in itself is not the first matter; for I can abstract from all my conceptions, but not from the ‘I.’ We think this and that, and hence it is—is to give the common would-be-wise argument of those incapable of grasping the matter in point; that a determinate content exists is exactly what we are forced to doubt—there is nothing absolutely fixed. Thought is the entirely universal, but not merely because I can abstract, but because ‘I’ is thus simple, self-identical. Thought consequently comes first; the next determination arrived at, in direct connection with it, is the determination of Being. The ‘I think’ directly involves my Being; this, says Descartes, is the absolute basis of all Philosophy.[158] The determination of Being is in my ‘I’; this connection is itself the first matter. Thought as Being and Being as thought—that is my certainty, ‘I’; in the celebrated Cogito, ergo sum we thus have Thought and Being inseparably bound together.
On the one hand this proposition is regarded as a syllogism: from thought Being is deduced. Kant more especially has objected to this that Being is not contained in thinking, that it is different from thinking. This is true, but they are still inseparable, or constitute an identity; their difference is not to the prejudice of their unity. Yet this maxim of pure abstract certainty, the universal totality in which everything implicitly exists, is not proved;[159] we must therefore not try to convert this proposition into a syllogism. Descartes himself says: “There is no syllogism present at all. For in order that there should be such, the major premise must have been ‘all that thinks exists’”—from which the subsumption would have followed in the minor premise, ‘now I am.’ By this the immediacy which rests in the proposition, would be removed. “But that major premise” is not set forth at all, being “really in the first instance derived from the original ‘I think, therefore, I am.’”[160] For arriving at a conclusion three links are required—in this case we ought to have a third through which thought and Being should have been mediated, and it is not to be found here. The ‘Therefore’ which binds the two sides together is not the ‘Therefore’ of a syllogism; the connection between Being and Thought is only immediately posited. This certainty is thus the prius; all other propositions come later. The thinking subject as the simple immediacy of being-at-home-with-me is the very same thing as what is called Being; and it is quite easy to perceive this identity. As universal, thought is contained in all that is particular, and thus is pure relation to itself, pure oneness with itself. We must not make the mistake of representing Being to ourselves as a concrete content, and hence it is the same immediate identity which thought likewise is. Immediacy is, however, a one-sided determination; thought does not contain it alone, but also the determination to mediate itself with itself, and thereby—by the mediation being at the same time the abrogation of the mediation—it is immediacy. In thought we thus have Being; Being is, however, a poor determination, it is the abstraction from the concrete of thought. This identity of Being and Thought, which constitutes the most interesting idea of modern times, has not been further worked out by Descartes; he has relied on consciousness alone, and for the time being placed it in the fore-front. For with Descartes the necessity to develop the differences from the ‘I think’ is not yet present; Fichte first applied himself to the deduction of all determinations from this culminating point of absolute certainty.