A History of Philosophy in Epitome

by Albert Schwegler

Rene Descartes (Renatus Cartesius) was born in 1596, at La Haye in Torraine. Possessing an independent property, he volunteered as a soldier in his twenty-first year, and served in the wars with the Dutch, the Bavarians, and the Imperialists. After this he travelled a good deal, and then abode a considerable time in Paris. In 1629 he left his native land, and betook himself to Holland, that he might there, undisturbed and unknown, devote himself to philosophy, and elaborate his scientific ideas. He spent twenty years in Holland, enduring much vexatious treatment from fanatical theologians, till in 1649 he accepted an invitation from Queen Christina of Sweden, to visit Stockholm, where he died in the following year.

The chief content of the Cartesian system may be seen condensed in the following epitome.

1. If science would have any thing fixed and abiding, it must begin with the primal ground of things; every presupposition which we may have cherished from infancy must be abandoned; in a word, we must doubt at every point to which the least uncertainty is attached. We must therefore doubt not only the existence of the objects of sense, since the senses so frequently deceive, but also the truths of mathematics and geometry—for, however evident the proposition may appear that two and three make five, or that the square has four sides, yet we cannot know but what God may have designedly formed us for erroneous judgments. It is therefore advisable to doubt every thing, in fact to deny every thing, to posit every thing as false.

2. But though we posit every thing as false to which the slightest doubt may be attached, yet we cannot deny one thing, viz., the truth that we, who so think, do exist. But rather from the very fact that I posit every thing as false, that I doubt every thing, is it manifest that I, the doubter, exist. Hence the proposition: I think, therefore I am (cogito ergo sum), is the first and most certain position which offers itself to every one attempting to philosophize. Upon this the most certain of all propositions, the certainty of all other knowledge depends. The objection of Gassendi that the truth of existence follows from any other activity of man as well as from thinking, that I might just as well say: I go to walk, therefore I exist,—has no weight; for, of all my actions, I can be absolutely certain only of my thinking.

3. From the proposition I think, therefore, I am, the whole nature of the mind may be determined. When we examine who we are who hold every thing to be false that is distinct from ourselves, we see clearly that neither extension nor figure, nor any thing which can be predicated of body, but only thought, belongs to our nature. I am therefore only a thinking being, i. e. mind, soul, intelligence, reason. Thought is my substance. Mind can therefore be apprehended clearly and completely for itself alone, without any of those attributes which belong to body. Its conception contains nothing of that which belongs to the conception of body. It is therefore impossible to apprehend it through any sensuous representation, or to make an image of it: it apprehends itself only through the pure intelligence.

4. From the proposition cogito ergo sum, follows still farther the universal rule of all certainty. I am certain that I am a thinking being, what now is involved in the fact that I am certain of any thing? Whence comes this certainty? From no other source than the knowledge that this first proposition contains a clear conception of that which I affirm. I know of a certainty that I am, and I know any thing else only when I know it as certainly as I know that I am. Hence I may regard it as a universal rule, that every thing is true which I know clearly and determinately.

5. This rule, however, is only a principle of certainty, not of knowledge and of truth. We apply it therefore to our thoughts or ideas, in order to discover what is objectively true. But our ideas are partly innate, partly acquired, and partly self-originated. Among those of the first class we find the idea of a God. The question arises, whence have we this idea? Manifestly not from ourselves; this idea could only be implanted within us by a being who has the fulness of all perfection in himself, i. e. only by an actually existing God. If I ask now the question, whence have I the faculty to conceive of a nature more perfect than my own? the answer must ever come, that I have it only from him whose nature is actually more perfect. All the attributes of God, the more I contemplate them, show that their idea could not have originated with myself alone. For though there might be in me the idea of substance because I am a substance, yet I could not of myself have the idea of an infinite substance, since I am finite; such an idea could only be given me through a substance actually infinite. Moreover, we must not think that the conception of the infinite is to be gained through abstraction and negation, as we might gain darkness through the negation of light; but I perceive, rather, that the infinite contains more reality than the finite, and that, therefore, the conception of the infinite must be correspondingly antecedent in me to that of the finite. Since then I have a clear and determined idea of the infinite substance, and since this has a greater objective reality than every other, so is there no other which I have so little reason to doubt. But now since I am certain that the idea of God has come to me from God himself, it only remains for me to examine the way in which I have received it from God. I have never derived it directly nor indirectly from the sense, for ideas through the sense arise only by affecting the external organs of sense; neither have I devised it, for I can neither add to it nor diminish it in any respect,—it must, therefore, be innate as the idea of myself is innate. Hence the first proof we can assign for the being of a God is the fact that we find the idea of a God within us, and that we must have a cause for its being. Again, the being of a God may be concluded from my own imperfection, and especially from the knowledge of my imperfection. For since I know that there is a perfection which is wanting in me, it follows that there must exist a being who is more perfect than I, on whom I depend and from whom I receive all I possess.—But the best and most evident proof for the being of a God is, in fine, that which is gained from the conception of a God. The mind among all its different ideas singles out the chiefest of all, that of the most perfect being, and perceives that this has not only the possibility of existence, i. e. accidental existence like all other ideas, but that it possesses necessary existence in itself. And as the mind knows that in every triangle its three angles are equal to two right angles, because this is involved in the very idea of a triangle, so does the mind necessarily infer that necessary existence belongs to the conception of the most perfect being, and that, therefore, the most perfect being actually exists. No other idea which the mind finds within itself contains necessary existence, but from the idea of the highest being existence cannot be separated without contradiction. It is only our prejudices which keep us from seeing this. Since we are accustomed in every thing to separate its conception from its existence, and since we often make ideas arbitrarily, it readily happens, that when we contemplate the highest being we are in doubt whether its idea may not be one also arbitrarily devised, or at least one in whose conception existence does not lie.—This proof is essentially different from that of Thomas (Anselm of Canterbury). His argument was as follows: “If we understand what is indicated by the word God, it is all that can be conceived of greatness; but now there is actually and in thought more belonging to him than the word represents, and therefore God exists not only in word (or representation), but in fact.” Here the defect in the syllogism is manifest, for from the premise it could only be concluded that God must therefore be represented as existing in fact, while his actual existence would not follow. My proof on the other hand is this,—we may predicate of a thing what we clearly see belongs to its true and changeless nature, or to its essence, or to its form. But now after we had examined what God is, we found existence to belong to his true and changeless nature, and therefore may we properly predicate existence of God. Necessary existence is contained in the idea of the most perfect being, not by a fiction of our understanding but because existence belongs to his eternal and changeless nature.

6. The result just found—the existence of God—is of the highest consequence. Before attaining this we were obliged to doubt every thing, and give up even every certainty, for we did not know but that it belonged to the nature of the human mind to err, but that God had created us for error. But so soon as we look at the necessary attributes of God in the innate idea of him, so soon as we know that he is true, it would be a contradiction to suppose that he would deceive us, or that he could have made us to err; for though an ability to deceive might prove his skill, a willingness to deceive would only demonstrate his frailty. Our reason, therefore, can never apprehend an object which would not be true so far as the reason apprehended it, i. e. so far as it is clearly known. For God might justly be styled a deceiver if he had given us a reason so perverted as to hold the false for the true. And thus every absolute doubt with which we began is dispelled. From the being of God we derive every certainty. For every sure knowledge it is only necessary that we have clearly known a thing, and are also certain of the existence of a God, who would not deceive.

7. From the true idea of God follow the principles of a philosophy of nature or the doctrine of the two substances. Substance is that which so exists that it needs nothing else for its existence. In this (highest) sense God is the only substance. God, as the infinite substance, has his ground in himself, is the cause of himself. The two created substances, on the other hand, the thinking and the corporeal substance, mind and matter, are substances only in a broader sense of the word; they may be apprehended under the common conception that they are things which need only the co-operation of God for their existence. Each of these two substances has an attribute which constitutes its nature and its essence, and to which all its other determinations may be referred. The attribute and essence of matter is extension, that of mind, thought. For every thing else which can be predicated of body presupposes extension, and is only a mode of extension, as every thing we can find in mind is only a modification of thought. A substance to which thought immediately belongs is called mind, and a substance, whose immediate substratum is extension, is called body. Since thought and extension are distinct from each other, and since mind cannot only be known without the attributes of the body, but is in itself the negation of those attributes, we may say that the essence of these substances is in their reciprocal negation. Mind and body are wholly distinct, and have nothing in common.