(La Haye, France, 1596 – Stockholm, Sweden, 1650) French philosopher and mathematician. After the splendour of ancient Greek philosophy and the apogee and crisis of scholasticism in medieval Europe, the new airs of the Renaissance and the scientific revolution that accompanied it would give rise, in the seventeenth century, to the birth of modern philosophy.
The first of the philosophical isms of modernity was rationalism; Descartes, its initiator, proposed to make a clean sweep of tradition and build a new building on the basis of reason and with the effective methodology of mathematics. His «methodical doubt» did not question God, quite the contrary; however, like Galileo, he had to suffer persecution because of his ideas.
René Descartes was educated at the Jesuit College of La Flèche (1604-1612), then one of the most prestigious in Europe, where he enjoyed a certain amount of favourable treatment for his delicate health. The studies that he carried out in such a centre had a decisive importance in his intellectual formation; known the turbulent youth of Descartes, undoubtedly in La Flèche the base of his culture had to be cemented. The traces of such education are manifested objectively and markedly in the whole philosophical ideology of the sage.
The curriculum of that school (according to various testimonies, including Descartes’ own) was very varied: it revolved essentially around the traditional teaching of the liberal arts, to which were added notions of theology and practical exercises useful for the life of future gentile men. Although the programme itself was to be rather light and essentially practical (it was not intended to train wise men, but men prepared for the high political missions to which their rank allowed them to aspire), the most active or curious students could supplement them on their own through personal readings.
Years later, Descartes would bitterly criticize the education received. It is perfectly possible, however, that his dissatisfaction in this respect comes not so much from philosophical considerations as from the natural reaction of an adolescent who for so many years was subjected to discipline, and from the feeling of uselessness of all that he learned in relation to his possible future occupations (bureaucracy or militia). After his time at La Flèche, Descartes obtained a bachelor’s degree and a law degree from the Faculty of Poitiers (1616), and at the age of twenty-two he left for the Netherlands, where he served as a soldier in the army of Maurice of Nassau. In 1619 he joined the ranks of Maximilian I of Bavaria.
According to Descartes himself in the Discourse on Method, during the harsh winter of that year he found himself blocked in a locality of the Upper Danube, possibly near Ulm; there he remained locked up next to a stove and far from any social relationship, with no other company than that of his thoughts. In such a place, and after a strong crisis of skepticism, the bases on which he would build his philosophical system were revealed to him: the mathematical method and the principle of cogito, ergo sum. Victim of a feverish excitement, during the night of November 10, 1619 he had three dreams, in the course of which he intuited his method and knew his deep vocation to devote his life to science.
After giving up his military life, Descartes travelled to Germany and the Netherlands and returned to France in 1622, to sell his possessions and thus secure an independent life; he spent some time in Italy (1623-1625) and then settled in Paris, where he became acquainted with most of the scientists of the time.
In 1628 he decided to settle in Holland, a country in which scientific research enjoyed great consideration and, moreover, was favoured by a relative freedom of thought. Descartes considered that it was the most favorable place to fulfill the philosophical and scientific objectives that he had set himself, and he resided there until 1649.
The first five years were devoted mainly to developing his own system of the world and his conception of man and the human body. In 1633, the writing of an extensive text of metaphysics and physics entitled Treatise on Light must have been well advanced; however, the news of Galileo’s condemnation frightened him, since Descartes also defended Copernicus’ heliocentrism in that work, an opinion that he did not believe to be censurable from the theological point of view. As he feared that such a text might contain condemnable theories, he renounced its publication, which would take place posthumously.
In 1637 his famous Discourse on Method appeared, presented as a prologue to three scientific essays. For the audacity and novelty of the concepts, the genius of the discoveries and the impetus of the ideas, the book was enough to give to its author an immediate and deserved fame, but also for this reason it provoked a flood of polemics, that from now on would make his life tiring and even dangerous.
which to base knowledge solidly. He found this principle in the existence of his own doubting conscience, in its famous formulation «I think, therefore I am». On the basis of this first evidence he was able in part to retrace the path of his skepticism, finding in God the ultimate guarantor of the truth of the evidences of reason, which manifest themselves as «clear and distinct» ideas.
The Cartesian method, which Descartes proposed for all sciences and disciplines, consists of breaking down complex problems into progressively simpler parts until we find their basic elements, the simple ideas, which are presented to reason in an evident way, and proceeding from them, by synthesis, to reconstruct the whole complex, demanding from each new relationship established between simple ideas the same evidence of them. The scientific essays that followed the Discourse offered a compendium of his physical theories, among which his formulation of the law of inertia and a specification of his method for mathematics stand out.
The foundations of his mechanistic physics, which made extension the main property of material bodies, were exposed by Descartes in the metaphysical Meditations (1641), where he developed his demonstration of the existence and perfection of God and of the immortality of the soul, already pointed out in the fourth part of the Discourse of the method. The radical mechanicism of Descartes’ physical theories, however, determined that they were later overcome.
As his fame and the spread of his philosophy grew, criticism and threats of religious persecution increased from some academic and ecclesiastical authorities, both in the Netherlands and in France. Born in the midst of discussions, the metaphysical Meditations had to be worth several accusations promoted by the theologians; something like that happened during the writing and publishing other works of his, such as The Principles of Philosophy (1644) and Passions of the Soul (1649).
Tired of these struggles, in 1649 Descartes accepted the invitation of Queen Christine of Sweden, who exhorted him to move to Stockholm as her preceptor of philosophy. Previously they had maintained an intense correspondence, and, in spite of the intellectual satisfactions that Cristina provided him, Descartes was not happy in «the country of the bears, where the thoughts of the men seem, like the water, to metamorphose in ice». He was accustomed to comforts and it was not easy for him to wake up every day at four in the morning, in full darkness and with the winter cold gnawing at his bones, in order to indoctrinate a queen who did not have more free time due to her obligations. The early Spartans and the cold could do more than the philosopher, who died of pneumonia in early 1650, five months after his arrival.
Descartes is considered the initiator of modern rationalist philosophy for his approach and resolution of the problem of finding a foundation of knowledge that guarantees its certainty, and as the philosopher who represents the definitive point of rupture with scholasticism. In the Discourse on Method (1637), Descartes stated that his project to develop a doctrine based on entirely new principles came from disenchantment with the philosophical teachings he had received.
Convinced that the whole reality responded to a rational order, his purpose was to create a method that would make it possible to reach in all the field of knowledge the same certainty that arithmetic and geometry provide in their field. His method, set forth in the Discourse, consists of four precepts or procedures: not to accept as true anything that is not absolutely certain to be true; to break down each problem into its minimum parts; to go from the most understandable to the most complex; and, finally, to completely revise the process in order to be sure that there is no omission.
The system used by Descartes to fulfill the first precept and achieve certainty is «methodical doubt». Following this system, Descartes questions all his acquired or inherited knowledge, the testimony of the senses and even his own existence and that of the world. However, there is something in every doubt that we cannot doubt: the same doubt. In other words, we cannot doubt that we are doubting. Thus we arrive at a first absolute and evident certainty that we can accept as true: we doubt.
I think, therefore I am
Doubt, Descartes reasoned, is a thought: to doubt is to think. Now, it is not possible to think without existing. The suspension of any concrete truth, the doubt itself, is an act of thought which immediately implies the existence of the thinking «I». Hence its famous formulation: I think, then I am (cogito, ergo sum). Therefore, we can be firmly sure of our thought and our existence. We exist and we are a thinking, spiritual substance.
It is from this that Descartes elaborates his entire philosophy. Since he cannot trust things, whose existence he has not yet been able to prove, Descartes tries to start from thought, whose existence has already been demonstrated. Although it may refer to the outside, thought is not composed of things, but of ideas about things. The question that arises is whether there is in our thinking any idea or representation that we can perceive with the same «clarity» and «distinction» (the two Cartesian criteria of certainty) with which we perceive ourselves as thinking subjects.
Types of ideas
Descartes then goes on to review all the knowledge he had previously discarded at the beginning of his search. And when he reconsiders them, he observes that the representations of our thought are of three kinds: «innate» ideas, such as those of beauty or justice; «adventitious» ideas, which come from external things, such as those of stars or horses; and «fictitious» ideas, which are mere creations of our fantasy, such as, for example, the monsters of mythology.
The «fictitious» ideas, mere addition or combination of other ideas, can obviously not serve as a handle. And with regard to «adventitious» ideas, originated by our experience of external things, it is necessary to act with caution, since we are not sure that external things exist. It could happen, says Descartes, that «adventitious» knowledge, which we consider to correspond to impressions of things that really exist outside of us, would have been provoked by a «malignant genius» who wanted to deceive us. Or that what seems to us to be reality is nothing more than an illusion, a dream from which we have not awakened.
From Me to God
But when we examine the «innate» ideas, with no sensible external correlate, we find in ourselves a very singular idea, because it is completely far from what we are: the idea of God, of an infinite, eternal, immutable, perfect supreme being. Human beings, finite and imperfect, can form ideas such as «triangle» or «justice». But the idea of an infinite and perfect God cannot be born of a finite and imperfect individual: it has necessarily been placed in the minds of men by Providence itself.
Therefore, God exists; and being as he is a most perfect being, he cannot deceive nor deceive us, nor allow the existence of an «evil genius» to deceive us, making us believe that a world that does not exist is real. The world, therefore, also exists. The existence of God thus guarantees the possibility of true knowledge.
This demonstration of the existence of God is a variant of the ontological argument already used in the twelfth century by St. Anselm of Canterbury, and was harshly attacked by Descartes’ adversaries, who accused him of falling into a vicious circle: in order to demonstrate the existence of God and thus guarantee knowledge of the outside world, the criteria of clarity and distinction are used, but the reliability of such criteria is in turn justified by the existence of God.
Such criticism points not only to the validity or invalidity of the argument, but also to the fact that Descartes does not seem to apply his own methodology at this point.
Res Cogitans and Res Extensa
Having admitted the existence of the outside world, Descartes goes on to examine what the essence of beings is. He introduces here his concept of substance, which he defines as that which «exists in such a way that it only needs itself to exist». Substances manifest themselves through their modes and attributes.
Attributes are essential properties or qualities that reveal the determination of the substance, that is to say, they are those properties without which a substance would cease to be such a substance. Modes, on the other hand, are not essential properties or qualities, but merely accidental.
The attribute of bodies is extension (a body cannot lack extension; if it lacks extension it is not a body), and all other determinations (colour, form, position, movement) are only modes. And the attribute of the spirit is thought, for the spirit «always thinks».
There is, therefore, a thinking substance (res cogitans), lacking in extension and whose attribute is thought, and a substance which composes physical bodies (res extensa), whose attribute is extension, or, if preferred, three-dimensionality, quantitatively measurable in a three-dimensional space. Both are irreducible to each other and totally separate. This is what is called Cartesian «dualism».
Inasmuch as the substance of matter and bodies is the extension, and inasmuch as this is observable and measurable, it must be possible to explain their movements and changes through mathematical laws.
This leads to a mechanistic view of nature: the universe is like an enormous machine whose functioning we can get to know through the study and discovery of the mathematical laws that govern it.
Communication of Substances
The radical separation between matter and spirit is applied rigorously, in principle, to all beings. Thus, animals are nothing more than very complex machines. However, Descartes makes an exception when it comes to man.
Since it is composed of body and soul, and being the material and extensive body (res extensa), and the spiritual and thinking soul (res cogitans), there should be absolute incommunication between them.
However, in the Cartesian system this does not happen, but the soul and the body communicate with each other, not in the classical way, but in a singular way. The soul is seated in the pineal gland, situated in the encephalon, and from there governs the body as «the nauta governs the ship», by means of animal spirits, intermediate substances between spirit and body as very fine particles of blood, which transmit to the body the orders of the soul.
Descartes’ solution was not satisfactory, and the so-called problem of the communication of substances would be discussed at length by later philosophers.
Descartes and Mathematics
We will briefly describe the brightest of his great contributions, omitting all the many beautiful things he did in Algebra and particularly in algebraic notation and equation theory.
It is something of a higher order, characterized by the kind simplicity of half a dozen of the greatest contributions made to Mathematics.
Descartes reworked Geometry and made modern Geometry possible. The basic idea; like all great things in Mathematics, is very simple and obvious.
If two straight lines that are cut are drawn on a plane, we can accept that the lines form right angles or any other type of angles. Imagine now a city built according to the American plan, whose avenues run from North to South and the streets from East to West.
The whole plan is traced with respect to an avenue and a street called axes, which are cut into what is called the origin, from which streets and avenues are numbered consecutively. Thus it is clearly appreciated, without the need for a diagram, where 126th Street is: 1002 to the West taking into account that 10 avenues add up to 1002, and then it is necessary to go west, that is, on the map to the left of the origin.
This is so familiar that it is easy for us to instantly fix the position of any direction. The number of avenues and the number of streets with the necessary supplements of smaller numbers (such as «2» or «1002») enables us to definitively and unequivocally establish the position of any point with respect to the axes, since the pair of numbers that measure its East-West and its North-South from the axes is known.
This pair of numbers is called the coordinates of the point (with respect to the axes). Suppose now a point that moves on the map. The coordinates (x, y) of all the points on the curve over which it moves will be bound by an equation (this must be accepted by the reader who has never plotted a graph), which is called the equation of the curve. Let us now assume for simplicity that our curve is a circumference.
We have its equation. What can we do with it? Instead of this particular equation, we can write a more general one of the same type (for example, the second degree whose coefficients of the variables multiplied from each other give the independent term and then proceed to treat this equation algebraically.
Finally we will refer to the results of all our algebraic manipulations in their equivalents as a function of the coordinates of points in the diagram, which all this time we had deliberately forgotten.
Algebra is easier to see than a spider web of lines in the Greek form of elementary Geometry. What we have done is to use our Algebra for the discovery and investigation of geometric theorems referring to circumferences.
«It is a completely different thing to consider (as in the use of coordinates) a general method and follow to the end the idea it represents. It is exactly this merit, whose importance all mathematicians know, that must be attributed to Descartes’ Geometry».
This is how he arrived at what… is a true great discovery in matter: the application of the method of coordinates, not only to make the transformation of equations of curves already defined geometrically, but contemplating the question from a point of view exactly opposite, for an a priori definition of curves increasingly complicated and, therefore, more and more general.
«Directly, with Descartes himself, later indirectly, on returning in the next century in the opposite direction, the whole concept of the object of mathematical science has been revolutionized.
Descartes understood the significance of what he had done and rightly said, when he wanted to boast, that he had surpassed Geometry before him to the same degree that Cicero’s rhetoric surpassed ABC.
As much for not having satisfactorily defined the notion of substance as for the frank dualism established between the two substances, Descartes raised the fundamental problems of the European speculative philosophy of the seventeenth century.
Understood as a strict and closed system, Cartesianism did not have excessive followers and lost its validity in a few decades. However, Cartesian philosophy became a point of reference for a large number of thinkers, sometimes to try to resolve the contradictions it contained, as did rationalist thinkers, and other times to refute it head-on, as did empiricists.
Thus, Nicholas Malebranche tried, with his occasionalist doctrine, to reconcile Cartesianism with the philosophy of Saint Augustine. The German philosopher Gottfried Wilhelm Leibniz and the Dutch Baruch Spinoza established forms of psychophysical parallelism to explain the communication between body and soul. Spinoza, in fact, went even further, and affirmed that there was only one substance, which encompassed in itself the order of things and ideas, and of which the res cogitans and the res extensa were nothing but attributes, which led to pantheism.
From a completely opposite point of view, the British empiricists Thomas Hobbes, John Locke and David Hume denied that the idea of a spiritual substance was demonstrable; they affirmed that there were no innate ideas and that philosophy should be reduced to the realm of experience.
The Cartesian conception of a mechanistic universe, in short, decisively influenced the genesis of classical physics, whose foundational milestone would be the publication of the Mathematical Principles of Natural Philosophy (1687), a work in which Newton established the three fundamental principles of dynamics, also called Newton’s laws.
It is no exaggeration to assert, in short, that while Descartes failed to solve many of the problems he raised, those problems became central questions of Western philosophy.
In this sense, modern philosophy (rationalism, empiricism, idealism, materialism, phenomenology) can be considered as a development or a reaction to Cartesianism.
Source: Biographies and lives