Descartes
(1596-1650)

Dr. Ess

[Taken from: W. T. Jones, Hobbes to Hume: A History of Western Philosophy, Vol. III, 2nd ed. (1969) Harcourt Brace Jovanovich, Inc. (pp. 154-189), with additional comments from Oldroyd, The Arch of Knowledge.]

- Descartes had a sense of novelty of the age in which he lived, and a contempt for all past learning, and a supreme confidence in the capacity of the human intellect to solve all human problems.

Overview:

Additional Philosophical Views:

THE METHOD - Some important rules from Descartes' Rules for the Direction of the Mind:

RULE III. In the subjects we propose to investigate, our inquiries should be directed, not to what others have thought, nor to what we ourselves conjecture, but to what we can clearly and perspicuously behold and with certainty deduce; for knowledge is not won in any other way....

- Two ways to "arrive at the knowledge of things":

(a) intuition - ...not the fluctuating testimony of the senses, nor the misleading judgment that proceeds from the blundering constructions of imagination, but the conception which an unclouded and attentive mind give us so readily and distinctly that we are wholly freed from doubt that which we understand...intuition...springs from the light of reason alone....

(b) deduction - ...we understand all necessary inference from other facts that are known with certainty. [For] many things are known with certainty, though not by themselves evident, but only deduced from true and known principles by the continuous and uninterrupted action of a mind that has a clear vision of each step in the process. It is in a similar way that we know that the last link in a long chain in connected with the first, even though we do not take in by means of one and the same act of vision all the intermediate links on which that connection depends, but only remember that we have taken them successively under review and that each single one is united to its neighbour, from the first even to the last....

RULE IV. There is need of a method for finding out the truth.

RULE V. Method consists entirely in the order and disposition of the objects towards which our mental vision must be directed if we would find out any truth. We shall comply with it exactly if we reduce involved and obscure propositions step by step to those that are simpler, and then starting with the intuitive apprehension of all those that are absolutely simple, attempt to ascend to the knowledge of all others by precisely similar steps. [in Oldroyd, 69]

[Oldroyd importantly points out, "Yet despite the seeming traditional character of the procedure, Descartes did have something new in mind. He supposed (in Rule 12) that the mind could form mental images of geometrical forms by the direct impression of ideas in the brain; and the vis cognoscens (cognitive awareness) could be aware of these `ideas' - either directly in direct sensation or subsequently in acts of memory. This epistemological thesis was supposed to provide the underpinning of the methodological directives of the Regulae For the mind could supposedly manipulate geometrical lines and figures in the brain (or the imagination), thereby solving certain algebraic problems geometrically. However, towards the end of the Regulae it would seem that Descartes came to realize that his project was untenable. One could not do general algebgra (for example, the solution of quadratic and higher-order equations) by the simple mental manipulation of lines and rectangles. So the program came unstuck, and the Regulae were left incomplete, only being published posthumously. (Oldroyd, 69)]

RULE VI. In order to separate out what is quite simple from what is complex, and to arrange these matters methodically, we ought, in the case of every series in which we have deduced certain facts the one from the other, to notice which fact is simple.... (1) We must note first that for the purpose of our procedure, which does not regard things as isolated realities, but compares them with one another in order to discover the dependence in knowledge of one upon the other, all things can be said to be either absolute or relative. (2) Secondly, we must note that there are but few pure and simple essences....These we say should be carefully noticed, for they are just those facts which we have called the simplest in any single series. All others can only be perceived as deductions from these, either immediate and proximate, or not to be attained save by two or three or more acts of inference....So pronounced is everywhere the inter-connection of ground and consequence, which gives rise, in the objects to be examined, to those series to which every inquiry must be reduced, that it can be investigated by a sure method....

RULE VIII. If the matters to be examined we come to a step in the series of which our understanding is not sufficently well able to have an intuitive cognition, we must stop short here. We must make no attempt to examine what follows; thus we shall spare ourselves superfluous labor.

COMMENT ON DESCARTES' METHOD - The assumption that there is in all men a native power adequate to know a reality that is fundementally rational combined the best insights in the Greek and Christian traditions. The Greeks assumed that reason is an adequate power, but they held that is not equal in all men. The early Christians took little or no account of reason, but they assumed all men are morally equal before God. By making reason adequate and equal in all men, Descartes laid the intellectual basis for the social and political institutions of democracy.

[Warning! On some readings of Descartes, this apparent "egalitarianism" is alleged to be part of a rhetorical "cover" for a radical project - namely, the establishment of a uniquely modern metaphysics which includes simply human beings and the natural order (i.e., not God).]

DESCARTES' MATHEMATICAL MODEL - Descartes believed that there is an objective, rational order in the world, an order that the mind infallibly discerns in its clear and distinct intuitions. - For Descartes, mathematical knowledge was absolute; it was an insight into an objective and rational real. Mathematical reasoning was the basis on which a great metaphysical structure, including a system of values and a God, could be erected.

THE SELF and DOUBT - Descartes held that in geometry one starts from self-evident and independent truths and arranges the various theorems that depend on these truths in proper order. So, in philosophy, Descartes held that one must look first for some metaphysical "absolute" and then for the various theorems that, when arranged in proper order, will yield an absolutely certain science of reality. Science was an insight into the nature of an objective and rational reality. - One was to proceed in the search for a metaphysical absolute by challenging every belief, however widely accepted and plausible it might be, in order to see whether it in fact met the test of certainty. - Descartes' doubt was methodological: He undertook simply to suspend his beliefs until he could prove them conclusively. Given an absolute starting point, he would begin a reconstruction in the course of which his former beliefs would be reinstated as they were deduced in accordance with the new and infallible method that he had derived from his study of geometry.

COGITO ERGO SUM - Descartes found one thing that he certainly and infallibly knew - that he doubted. If you try to doubt your own existence, this doubt disproves itself. One must surely exist in order to doubt that one exists. - Here in his certainty of his own existence, Descartes had the "absolute," the indubitable truth, that he needed as a starting point for his science of reality. Accordingly, he proposed to follow his own rules - to arrange his thoughts in "due order" and to advance by a series of simple steps, each of which could be seen to be clearly and distinctly true. The road proved to lead from self to God, and from God to the physical world.

GOD: PROOF OF GOD'S EXISTENCE

(1) Everything, including our ideas, has a cause.

(2) We have an idea of God.

(3) Nothing less than God is adequate to be the cause of our idea of God.

Therefore, (4) God exists.

[Oldroyd's conception of the argument:

A1 (1) Descartes knew that he did not know everything with certainty. Therefore

(2) He acknowledged himself to be imperfect (and he had the concept of imperfection in his mind).

A2 (1) For Descartes to have the idea of imperfection, he also had to have the idea of perfection.

(2) The idea of perfection could not have been in his mind unless there were a perfect being.

Therefore, (3) Therefore a perfect being exists - God. (Oldroyd, 70)]

CRITICISM OF THIS PROOF - There are two stages in the Cartesian proof, and each of them may be challenged:

[1] Do we really have a clear and distinct idea of an infinite and perfect being?

[2] Supposing that we do have such an idea, is God its only possible cause?

DIFFERENCES BETWEEN DESCARTES' AND PLATO'S VIEWS OF KNOWLEDGE - Though he held reason to be independent, Descartes did not think of it as the completely secular and self-sustaining power that Plato and Aristotle had conceived it to be. Descartes was not willing to let reason remain utterly secular. According to him, the "more" that validates our finite reason is not merely more reason. There is more reason, it is true; but behind the more reason there lurks a personal and transcendent God. - Intuition, usually conceived by Descartes as an active power in us, sometimes became a passive state in which we are illumined from above; and reason, far from being a searchlight that focuses a clear beam on real entities out there in the world beyond us, became a superillumination that fills our souls with transcendent light and truth.

THE PHYSICAL WORLD - The proof of the existence of the physical world rests on God's goodness and His power - on His will, not His reason. The fact that this proof depends on God's will, instead of on His reason, is a sign that Descartes recognized that there is a distinction between "corporeal nature in so far as it is the object of pure mathematics" and corporeal nature as extended magnitude. - If his proof of the existence of matter is valid, the physical world is God's creature, an expression of His providence; yet it runs according to mechanical law and can be completely understood without any further reference to purposes or final causes.

DESCARTES' CONCEPTION OF SUBSTANCE - That substances exist seemed so obvious to Descartes that he held we must "conclude" that a substance is "neccessarily present" wherever we encounter a property, even though the substance in question is "not observed by us." Hence it never occurred to him to subject the concept of substance to criticism in accordance with his program of systematic doubt, even though he was prepared to doubt the existence of things that are "observed by us."

THE CARTESIAN COMPROMISE - If mind and body are completely different kinds of things, and if the truths about each follow from the distinct nature of each, it is impossible for the science of minds and the science of bodies to contradict each other. Theologians, therefore, have no reason to interfere with the study of physics, and physicists have no reason to claim any special competence regarding spiritual truths. Further, men need never fear, for instance, that minds, as well as bodies, are determined by antecedent events in time; nor is there any danger that free will, moral responsibility, and God will prove to be merely subjective illusions in a materialistic universe. There can be no conflict between science and religion, for each is sovereign in its own sphere and neither has any standing in the sphere of the other.

NATURE OF MATERIAL THINGS - The physical world, Descartes held, is a material plenum; all change is local motion of various parts of this plenum; since this motion conforms to simple, mathematically statable laws, it is capable of being predicted with complete certainty. - The net result of Descartes' identification of material substance with extension and of extension with space was to make physics an absolutely certain science. For by means of this double identification, geometry, which is the absolutely valid science of the properties of space, becomes the instrument by which the nature of material things is to be investigated.

NATURE OF MIND - Everything in the created universe that is not a body is a mind, or self. Since each of us is a self, we know the nature of mind much better than we know the nature of body, and we "observe many more qualities in our mind than in any other thing."

VOLITION - Religious and moral considerations made it seem essential to Descartes to establish the freedom of the will.

UNDERSTANDING - Distinction between:

(1) thinking - which is cognition of the world as it is, namely, a universe of unextended minds and of material substances possessing only "length, breadth, and depth."

(2) sensing - which is perception of a world of colored, sounding, and odorous bodies. - If a mind and its objects are different substances, how does a mind come to know its objects? It cannot go out in the world to study it in situ, nor can the world, concieved of as matter in motion, come into the mind. A cognitive link between mind and world was thus needed. This link, which Descartes called an "idea," is a state of the mind, and a true idea represents in the mind the object out there that is its cause.

DOCTRINE OF INNATE IDEAS - As long as ideas are regarded as the mental links between minds and their world, it is necessary to distinguish between:

Descartes' whole position depends on the assertion that our ideas of simple natures are adequate; and he could make sure of their adequacy only by claiming that our ideas of simple natures have been implanted in us by God, that is, that they are innate.

PERCEPTION - The main trouble with perception is simply that men tend to take it at face value. They ignore the distinction just pointed out, and, "perverting the order of nature," they assume that the senses yield information about "the essence of the bodies which are outside" them. If, however, men learn not to expect more of perception than it can give, they will find that, for the purposes of ordinary life, it is not a bad guide.

INTERACTION - If mind and body are the two distinct substances that the Cartesian compromise required them to be, how can they interact in sense perception and emotion? According to Descartes, interaction occurs in the pineal gland, which is located between the two hemispheres of the brain. - The major problem that Descartes faced was how to save the Cartesian compromise. Unfortunately the mind and the body meet at least at one point - in man. A man's mind acts on his body and his body acts on his mind. But the assertion that a completely free mind produces changes in its body is ultimately fatal for the Cartesian compromise.

[Oldroyd sees Descartes' metascience as structured like the `arch' with his emphasis chiefly on the `downward', deductive limb - i.e., deductions drawn from the first principles of a science, following the model of drawing conclusions from the first axioms of a mathematical system.