The Philosophy of René Descartes

René Descartes (1596-1650)

I. General Observations

René Descartes (picture) is justly considered the father of modern philosophy and the founder of the rational method as applied to philosophical research. In fact, he is the first philosopher to begin with the impressions which are in our intellect (intellectual phenomenalism) and lay down the laws which reason must follow in order to arrive at reasonably certain philosophical data.

This phenomenalism does not find its full development in Descartes. Indeed, Descartes reaches metaphysical conclusions which are no different from those of Scholastic philosophy. He maintains the transcendency of God, upholds human liberty and Christian morality.

But pantheism is sown deep in every form of immanentism. The rationalism of Descartes was to be quickly and logically bent in this direction by Spinoza, while other Cartesians, such as Malebranche and Leibniz, tried -- with less logic -- middle-of-the-road solutions between pantheism and the transcendence of God.

II. Life and Works

Descartes was born in 1596 at La Haye in France of a noble family, and was educated in the celebrated Jesuit college of La Flèche, where he received a philosophical and scientific education according to the principles of the Scholasticism of his day. Not fully satisfied with this first education, and urged on by a desire to better himself, he went first to Paris, and then enlisted in the army during the Thirty Years' War.

On the ninth of November, 1619, while still in the service in winter quarters, he gave himself up to meditating on how to apply the mathematical method of the sciences to philosophy. During this time he conceived the four laws which he described in his work Discourse on Method. He then abandoned the army, but before dedicating himself completely to philosophical meditation he undertook long travels throughout Europe.

In 1629 he retired to Holland, which offered him tranquillity for meditation and writing. He remained there until 1649. During these twenty years he wrote nearly all his books. In 1649 he went to the court of Queen Christina of Sweden, being summoned there by the Queen, who wished to study philosophy under his direction. Unable to resist the rigors of winter, he died in Sweden during 1650.

Descartes was a scientist and a philosopher. As a scientist he is noted for his studies in mechanics, physics and mathematics. As a philosopher he opened the period of modern philosophy.

Not all the philosophical works written by Descartes were published during his lifetime. His Rule for the Direction of the Mind was published posthumously, as was his treatise on The World.

The philosophical works published by the author were four: Discourse on Method; Meditations on First Philosophy, in which he proves the existence of God and the immortality of the soul; Principles of Philosophy, in four books, a systematic work reviewing the entire thought of the author; The Passions of the Soul, treating of the problem of morality.

III. The Laws of the Cartesian Method

Descartes, in his work Discourse on Method, after giving a criticism of the education which he had received (a criticism which is indirectly an attack on the Scholasticism of his day), goes on to set up the new method, according to him, must be the basis of all scientific and philosophical research.

These laws are four:

To accept nothing as true that is not recognized by the reason as clear and distinct;
To analyze complex ideas by breaking them down into their simple constitutive elements, which reason can intuitively apprehend;
To reconstruct, beginning with simple ideas and working synthetically to the complex;
To make an accurate and complete enumeration of the data of the problem, using in this step both the methods of induction and deduction.
To better understand these laws, we must note that for Descartes the point of departure is the ideas, clearly and distinctly known by the intellect -- the subjective impressions on the intellect. Beyond these clear and distinct ideas one cannot go, and hence the ultimate principle of truth consists in the clearness of the idea. Clear and distinct intuitions of the intellect are true. For Descartes, such clear and distinct intuitions are thought itself ("cogito") and the idea of extension.

Having arrived at this starting point (clear and distinct ideas), the intellect begins its discursive and deductive operation (represented by the second and third rules). The second law (called analysis) directs that the elementary notions be reunited with the clear and distinct ideas (the minor of the Scholastic syllogism). The third law (synthesis) presents them as the conclusion flowing from the premises. The final law (complete enumeration) stresses that no link in the deductive chain should be omitted and that every step should be logically deduced from the starting point (i.e., from the clear and distinct ideas). Thus, working from one step to the next, there will be achieved a system of truths all of which are clear and distinct, because all participate in the same degree of truth enjoyed by the first idea, which was clear and distinct.

This, as we know, is the method adopted in mathematics. Descartes transferred it to philosophy with the intention of finding clear and distinct concrete ideas, and of deducing from these, through reason alone, an entire system of truths which would also be real or objective.

The Aristotelio-Scholastic method (as well as that of classical realism in general) is also deductive, but it is very different from that of Descartes. Scholastic deduction is connected with objective reality because ideas are abstractions of the forms of the objects which experience presents. Thus both the concreteness of the ideas and the concreteness of the deductions based on these ideas are justified.

In Descartes ideas do not come from experience, but the intellect finds them within itself. Descartes declares that only these ideas are valid in the field of reality. Thus the concreteness (or the objective validity) of an idea is dependent upon its own clearness and distinction.

IV. Metaphysics: From Methodical Doubt to "Cogito Ergo Sum"

Descartes, as a result of the principles already established in his method, had first of all to seek out a solid starting point (a clear and distinct concrete idea), and from this opens his deductive process. To arrive at this solid starting point, he begins with methodical doubt, that is, a doubt which will be the means of arriving at certitude. This differs from the systematic doubt of the Skeptics, who doubt in order to remain in doubt.

I can doubt all the impressions that exist within my knowing faculties, whether they be those impressions which come to me through the senses or through the intellect. Indeed, I may doubt even mathematical truths, in so far as it could be that the human intelligence is under the influence of a malignant genius which takes sport in making what is objectively irrational appear to me as rational.

Doubt is thus carried to its extreme form. But notwithstanding this fact, doubt causes to rise in me the most luminous and indisputable certainty. Even presupposing that the entire content of my thought is false, the incontestable truth is that I think: one cannot doubt without thinking; and if I think, I exist: "Cogito ergo sum."

It is to be observed that for Descartes the validity of "Cogito ergo sum" rests in this, that the doubt presents intuitively to the mind the subject who doubts, that is, the thinking substance. In this, Cartesian doubt differs from that of St. Augustine ("Si fallor, sum"), which embodies a truth sufficiently strong to overcome the position of Skepticism. In Descartes, "Cogito ergo sum" is assumed, not only in order to overcome the Skeptic position but as a foundation for the primary reality (the existence of the "res cogitans"), from which the way to further research is to be taken.

This is the point which distinguishes the classic realistic philosophy from Cartesian and modern philosophy. With Descartes, philosophy ceases to be the science of being, and becomes the science of thought (epistemology). Whereas, at first, being conditioned thought, now it is thought that conditions being. This principle, more or less realized by the philosophers immediately following Descartes, was to reach its full consciousness in Kant and modern Idealism. (See: Meditations on First Philosophy, I and II; Discourse on Method, IV.)

V. From "Cogito" to the Proof of the Existence of God

The "cogito" reveals the existence of the subject, limited and imperfect because liable to doubt. It is necessary to arrive at an objective and perfect reality, i.e., to prove the existence of God.

Descartes makes use of three arguments which can be summarized thus:

"Cogito" has given me a consciousness of my own limited and imperfect being. This proves that I have not given existence to myself, for in such a case I would have given myself a perfect nature and not the one I have, which is subject to doubt.
I have the idea of the perfect: If I did not possess it, I could never know that I am imperfect. Now, whence comes this idea of the perfect? Not from myself, for I am imperfect, and the perfect cannot arise from the imperfect. Hence it comes from a Perfect Being, that is, from God.
The very analysis of the idea of the perfect includes the existence of the perfect being, for just as the valley is included in the idea of a mountain, so also existence is included in the idea of the perfect. (the argument of St. Anselm). (See: Meditations on First Philosophy, V; Discourse on Method, IV.)
Regarding the nature of God, Descartes ascribes to it more or less the same attributes as does traditional Christian theistic thought. In Descartes, however, these attributes assume a different significance and value. God, above all, is absolute substance: the only substance, properly so-called (hence the way is open to the pantheism of Spinoza). An attribute which has great value for Descartes is the veracity of God.

God, the most perfect being, cannot be deceived and cannot deceive. Thus the veracity of God serves as a guarantee for the entire series of clear and distinct ideas. They are true because if they are not true, I, having proved the existence of God, would have to say that He is deceiving by creating a rational creature who is deceived even in the apprehension of clear and distinct ideas. Thus, with the proof of the existence of God, the hypothesis of a malignant genius falls of its own weight.

Regarding the origin of ideas, Descartes holds that the idea of God, all primitive notions, all logical, mathematical, moral principles, and so forth, are innate. God is the guarantee of the truth of these innate ideas. Alongside these innate ideas Descartes distinguishes two other groups of ideas:

the adventitious, which are derived from the senses; and
the fictitious, which are fashioned by the thinking subject out of the former.
Both groups are considered of little worth by Descartes because they do not enjoy the guarantee of the divine veracity, and hence are fonts of error. Only innate ideas and the rational deduction made from them have the value of truth. (See: Meditations on First Philosophy, III.)

VI. The "Res Extensa" and the Mechanism of the Universe

Descartes proves the existence of the world, not from the testimony of our experience of this fact but from the innate idea of the "res extensa." We have a certain idea that is clear (presenting but one quality, extension), and it is distinct from the "res cogitans." This idea, granted the veracity of God, cannot be false; hence the world exists, and its principal attribute is extension.

Concerning the nature of this corporeal world, Descartes distinguishes between what is presented to us through the senses (colors, odors, tastes, tactile sensations) and that which comes by way of the intellect, i.e., dimension, figure, weight, position, motion. The first, not guaranteed by the veracity of God, do not have objective value; they are secondary qualities, modes with which the subject represents reality. The second which, according to Descartes, must be innate ideas, are primary qualities and are guaranteed by the veracity of God; hence they are real and objective.

The Cartesian World is characterized by the essential attribute of extension ("res extensa"), which is infinite. In this extension the power of God has placed force and movement, which are determined by the principle of absolute causality. Not purpose (finalism), but mechanical determination (matter and mathematical laws of motion) governs the succession of phenomena in the physical world, in the "res extensa." The world is a machine. The inorganic world, plants and animals, and even man, as far as his body is concerned, are machines governed by the laws of causality of motion.

VII. The Dualism of Substances

The entire Cartesian system rests upon a metaphysical dualism: "res cogitans" (God and the human soul) and "res extensa" (the corporeal world). These two realities are irreducible, in so far as thought, liberty and activity are essential to the world of the thinking being, and extension, mechanical determinism and passivity are essential to the world of the "res extensa." All reciprocal action between the two substances is excluded because it is impossible. Thus there is opened up the problem which was later to be taken up by rationalism: the determination of the relationship between spirit and matter; between God (the infinite spirit) and the world (finite matter).

This problem presented even graver difficulties in connection with the Cartesian concept of substance -- that which exists without need of the concursus of any other to exist. Such a definition of substance is applicable only to God, who because He is causa sui, is a substance that has no need of the concursus of another in order to exist. But finite beings also are substances; and although Descartes had added that finite beings need the concursus of God in order to exist, the passage to the monistic concept of single substance appears quite open; this was to be the point of departure for Spinoza.

To this we must add the fact that Descartes considers thought not as an act, but as the thinking substance ("res cogitans"), that is, as a soul, whose essence is thought. Now such an identification belongs only to God; hence it is easy to see in this teaching of Descartes the danger of unifying the concepts of man and God ("homo -- Deus") and hence the latent danger of pantheism.

In the world of Cartesian matter, there exist no qualities, but only quantity, matter and motion, which act fatally, necessarily and mechanically. The mechanistic concept was to be inherited by Rationalism and Empiricism, which considered the world as a huge machine acting through mechanical forces, without purpose.

VIII. Ethics

Cartesian Rationalism finds its application even in ethics. For Descartes, ethics is the science of the end of man, and this end must be determined by reason. Before reason can arrive at the knowledge of such an end, and of the means of reaching it, the philosopher and only the philosopher must construct a provisory morality, a model of life capable of assuring him tranquillity, a standard which he will follow until such time as definitive and rational morality appears to his reason. Provisory morality is made up of a few precepts: Live according to the politico-religious opinions and customs of the country; follow mean (i.e., moderate) and not extreme opinions; govern yourself with constancy, without letting yourself be distracted by opportunistic considerations. In a word, live in such a manner as to assure yourself the greatest tranquillity.

Regarding definitive morality, Descartes holds to the full liberty of God, so that all depends on the divine liberty. God, if He so wished, could have created a world governed by moral principles opposed to those which hold today. Such an idea brings ethics to the brink of disaster, for a morality like this would not find its justification in the absolute essence of God but in the arbitrary act of His will.

Granted the present order of creation, Descartes recognizes that the end of man is virtue and happiness. The actuation of this end is brought about through reason -- through the knowledge of God, of the soul, and of the world. It is attained through knowledge of God because God is the creator and unifier of the universe; of the soul, because the soul makes clear to us our superiority over material nature; of the physical world, because, governed by causal necessity, it teaches man the virtue of resignation and indifference in the face of the evils of life.

As is evident, Cartesian morality does not greatly differ from Stoic ethics in which the wise man appeals to reason in order to assure himself of tranquillity and felicity.

IX. The Development of Cartesian Rationalism

Descartes left two questions unsolved:

the determination of the relationship between the infinite substance (God) and finite substance (the world), and
the relationship between the spirit-substance (the soul) and the extended substance (body).
To fill the gap which he left between the infinite and finite, between spirit and matter, there were three possible solutions to be had through recourse to earlier philosophers. All three solutions were tried and developed by later philosophers: Spinoza, Malebranche and Leibniz, whose systems can justly be considered as developments of the rationalistic premises of Cartesian principles.

The first possible solution lay in uniting Cartesianism with Platonism and conceiving of the two Cartesian substances (thought-substance and extended substance) as attributes deriving from a single divine substance. This was the solution of Spinoza, the strongest and most coherent of the Cartesian thinkers. He abolished the distinction between finite and infinite, and explained monistically and pantheistically the procession of the finite from the infinite. Spinoza answered the first of the unsolved questions, that of the relationship between God and creatures. But he maintained the second distinction and determined the relationship between soul and body by a psycho-physical law: That which is produced in thought by its very nature finds determination in extension (body).

The second possible solution came from Augustinianism. Augustinianism, faced with the impossibility of deriving concepts from experience, had recourse to God, to a divine illumination in which God actually implants ideas in the human intellect. This supernatural intervention or influence could be extended to all finite reality in such a manner as to fill in the gap between the infinite and the finite, between spirit and matter, through the intervention of God Himself. This was the solution taken by Malebranche, according to whom creatures are the simple occasions; a direct intervention of God is the direct cause of all effects (Occasionalism).

As a Christian Malebranche maintains the distinction between God and the world, two forces which were unified in Spinoza. But in determining the relationship between God and the world, Malebranche also has recourse to God. This he achieves in such a manner that the immanentism latent in Cartesian Rationalism is not revealed in the concept of substance but in the relationship between the two substances.

The third possible solution was sought in bringing Cartesian Rationalism into harmony with Aristotelian Scholasticism, and attempting to fill in the relationship between spirit and matter with the concept of potency flowing spontaneously into act according to a law pre-established by God. This law would also explain the relationship between the finite and the infinite. The monad of Leibniz is developed according to a pre-established harmony; its development is a passage or transition from a potential state to a state of representation.

Despite these intrinsic deficiencies and notwithstanding the opposition which Cartesianism caused from its first appearance both in the field of philosophy (Gassendi, Hobbes) and in that of religion (both Catholic and Protestant), Cartesianism spread rapidly throughout Europe and represented the dominant thought of the period. It influenced all branches of culture. Catholic thinkers for example, those at noted centers like the Paris Oratory and the Benedictine abbey of Port-Royal, favored the supereminent position it gave to God and the soul. The Jansenist polemics which Cartesianism instigated are a proof of this; scientists liked the geometric spirit of the system; philosophers and litterateurs were pleased with the clear and distinct ideas and the spirit of criticism carried out according to rational methods. The classic land of Cartesianism, naturally, is France during its golden age of literature, the age of Louis XIV.

Empiricism also developed along with Cartesian Rationalism, and felt its influence. Certainly Empiricism is opposed to Rationalism as sensitive and intellective knowledge are in opposition. Nevertheless, it felt the influence of Cartesianism, first in a negative sense, in so far as Empiricism now rose to reaffirm its premises in its debates with Rationalism (Hobbes, Locke); in a positive way it was also influenced in so far as the principle of immanence in common to both Empiricism and Rationalism. We may conclude that Cartesianism, directly or indirectly, is that predominating tendency in the philosophy of this period; it prepares the way for Illuminism, and through Illuminism it reaches Kant.

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