RENÉ DESCARTES
(1596 to 1650)

Descartes: An Overview

His Major Ideas

His Legacy

Descartes' Writing

Galileo's and Kepler's work coincided in its timing almost exactly with the work of another early 17th century figure: René Descartes.  In some ways Descartes was a medieval rationalist--who believed (in keeping with Plato) that all things in the world around us are merely "extensions" of some variety of mathematical or geometric abstractions. The underlying truth about our world "out there" was discoverable really only through careful mathematical meditations on that world--which could be done at home or in one's closet. But in any case, what he came up with in his musings was the idea that the world "out there" was essentially a mechanical device that worked according to fixed rules of motion. Events occurred as the result of impacts among the various bodies that are in constant motion within this "machine."  The machine itself is devoid of soul or vitality of its own. It simply responds to the "laws" of motion in a mathematical way. But that left the question of the human soul and will--and the divine soul and will. Where do we fit in? Are we merely elements of this mechanical world? Is God merely an element of the mechanical world? To Descartes the answer was clearly a "no" to both questions. But in affirming our own vitality--and God's--Descartes was forced to separate the human soul (and God's) from that soul-less mechanical creation "out there." Fine. But how then were we connected to that world--except as removed observers? Where was our ancient sense of unity with all creation? Where in fact did that leave us in relation to God--and to each other? Those questions were never adequately answered. The human soul seemed to be left cut adrift by what was considered a very compelling philosophical statement--one which swept powerfully through the philosophical circles of Europe in those days.

The Search for Mathematical Formulations for Earthly Life Descartes is remembered as the true father of modern European Rationalism.  Impressed by the recent discoveries of Galileo and Kepler concerning the mathematical formulations that described simply and elegantly the movements of the heavens (permitting the world to set aside the horribly cumbersome formulations of the Ptolemaic tradition) Descartes jumped easily to the belief that all of life was undergirded by such pure or clear mathematical formulations.  Just as pure reason had discovered those celestial formulas, pure reason would surely also unlock the formulations for life here on earth. Believing this to be so, Descartes set about to begin just that task--to start to lay out the fundamental or foundational truths on which a mathematical edifice of formulas describing earthly life could subsequently be built, his Discourse on Method (1637). This Method was to go to the most fundamental of propositions that could be demonstrated through logic to be absolutely true--which for him had to be the reality of his own consciousness, the mind that posed the question in the first place.  It was also a natural starting point for him, given his underlying faith in the human mind's ability to embrace the mathematical undegirding of the universe. The Cogito Put another way, the Method was supposedly very rigorous in that it was willing to doubt to all propositions until it got to a point where there could be no further doubt.  And that point to him was his own thinking itself:  it could not be doubted that he was indeed thinking, even as he doubted!.  He could not certainly doubt that he was doubting!  Thus he was thinking.  That was an absolute certainty.  And for Descartes the inescapable conclusion was that if he were thinking, then he also had to exist:  cogito ergo sum.  I think therefore I am. To Descartes, this then was self-evident before the natural light of human reason.  He had not depended in any manner at all on mere philosophical tradition on which to ground his argument.  His methodology had set knowledge free from the dictates of dogma or convention--to be based on "fact" that was absolutely true.  Or so he claimed.  And the world basically agreed. From the cogito he then jumped to the idea that even though he cannot say with any certainty that things outside him exist--he can be certain that he is having thoughts about them.  Furthermore, these thoughts can easily embrace the idea of the existence of things in their perfect form--as for instance a perfect circle.  Here he is acknowledging the correctness of the Idealism of Pythagoras and Plato.  Along this line, his thoughts can embrace the idea of the existence of a perfect God. His Demonstration of God's Existence Where do such ideas come from?  He concludes that there has to be something beyond himself, "out there," that sets such thoughts into motion.  And that reality out there can not be less perfect than what his own thoughts can formulate--for how could he conceive of something as being more perfect than it actually is?  It could not come from his own mind--for his own mind is itself imperfect, given to doubt.  No--the Perfect then must exist beyond himself, giving rise to his present thoughts about such Perfection. From this he jumps (and it is a jump indeed) to the idea that the very Perfection of God is such that God could not deceive him.  Therefore the thoughts he was having about a Perfect God had to be true.  [Ingenius, but not very compelling logic!]  Further, being God by nature, God would not allow deceptive thoughts to come among us--that God would allow only real or true thoughts to come to Descartes' mind [Descartes does not allow for the existence of a Deceiver--other than his own flawed doubts]. Probing the Question of Physical Existence or "Physics" Now he moves in his thoughts (outlined in particular in his book Passions of the Soul) to the existence of the substance of his own body--which he treats as a physical  extension beyond his conscious mind or soul.  But the two, body and soul (or mind) are closely linked so that they affect each other directly (through the pineal gland, located at the base of the brain).  Nonetheless, it is only the body, as an extension, that is guided by the mathematical laws of physics.  [The soul, not being an extension of any kind, does not exist on the basis of these same laws.  It is of a different order of being.] Qualities such as color, sound, smell, temperature, flavor, etc.  related to extended substances are not extensions themselves but are "secondary" qualities--as opposed to the primary qualities such as mass and velocity or movement.  Only these primary qualities point to real existence.  Only these primary qualities respond to the laws of physics--mathematical laws describing the physical machinery called reality.  Descartes was very unclear in his thinking about how then these secondary qualities existed. Also, Descartes believed that all physical reality was a continuous substance--of varying concentrations of mass and of varying motions here and there throughout the cosmos.  The idea of a vacuum was inadmissible to him.

It was Descartes' thinking on this matter of substance, its physical "extension" as the only true base of existence, that got Newton to thinking--ultimately to refute Descartes' notions of mass and motion.  Locke also would reflect on Descartes' theories--and adopt some of his thinking about the differences between primary and secondary qualities of being. Of course physics has developed in such a way that many of Descartes ideas have been put aside.  But overall he was very persuasive in his effort to apply rational theories to the existence of physical matter here on earth.  He was very influential in getting "natural philosophers" (scientists) to begin to probe the nature of material being here on earth--as a matter now open to human enquiry. The purpose was no longer to apply human inquiry to physical life in order to discover magical formula for turning base elements into gold--but to explore physical reality simply for knowledge of such reality in and of itself.

Descartes' major works or writings: Discourse on the Method (1637) Meditations on the First Philosophy (1641) Principia Philosophiae (Principles of Philosophy) (1644) The Passions of the Soul (1649)

Go to the history section: Europe During of the First Half of the 1600s

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  Miles H. Hodges