René Descartes
Except our own thoughts, there is nothing absolutely in our power. ~ René Descartes
French mathematician and philosopher René Descartes (1596–1650) was born into wealth, affording him the best education. His inquisitive mind put it to vigorous use.
In fusing geometry with algebra, Descartes founded analytic geometry, which laid the foundation for infinitesimal calculus and mathematical analysis. Unsurprisingly, Descartes agreed with Galileo before him, and anticipated Newton in concluding that knowledge is ultimately, inexorably, mathematical.
In his search for philosophical truth Descartes decided that introspection was the path to knowledge: the same conclusion drawn a millennium earlier by Augustine. Descartes found some concepts so cogent that their truth was undeniable, even though they were outside personal experience.
Descartes mused that, despite his imperfection, he could entertain perfect abstractions (Platonic forms again). Because perfection could not arise from something imperfect, he concluded that he could not be the author of such concepts. Descartes thought these ideas innate.
The only hypothesis left was that this idea was put in my mind by a Nature that was really more perfect than I was, which had all the perfections that I could imagine, and which was, in a word, God. (The idea of a perfect God is an echo of Augustine.) ~ René Descartes
Supposing that a perfect God exists that does not deceive humans, Descartes consider the senses trustworthy as long as the sensory information is lucid. With this Descartes restored the dignity of subjective experience that had dimmed in Galileo’s wake. Descartes’ conjuring of objectivity paved the way for the scientific study of the mind.
With his mathematical bent (orientation to formula), Descartes considered physiology and behaviors as mechanistic. Sense receptors were like pressure plates that starting water flowing, activating nerves, which Descartes imagined as delicate hollow threads.
Perpetuated by the influential, 2nd-century Greek physician Galen, the idea of animal spirits (vitalism) was popular among the ancient Greeks, including Aristotle. The presence of animal spirits distinguished the living from the inert. Descartes incorporated vitalism into a fanciful conception of behavior: when animal spirits flowed to certain muscles, they invoked behavior.
Descartes considered behaviors reflexive: a stance which presaged behaviorism. In doing so, Descartes legitimized the destructive examination of animals to learn more about the apex animal: man. He himself did a great deal of dissecting.
Descartes concluded that all manner of ecological interactions, internal processes, and behaviors could be explained mechanically. Dreams were caused by a wash of animal spirits while asleep.
Even during his lifetime, Descartes’ fabrications of reflex were shown to be incorrect; but stubborn pride left Descartes unmoved.
Though the behaviors of humans and other animals obeyed the same mechanics, Descartes discriminated between the two, in that only humans had a mind. This made humans unique in possessing consciousness, rationality, free will, and a soul. (Descartes presumed the mind and the soul more or less the same substrate.)
For Descartes, the body is physical, but the mind is not. This bifurcation of mind-body cast Descartes as a promoter of dualism.
There is a great difference between mind and body. ~ René Descartes
Dualism posits 2 entangled facets of existence for life forms: the physical and the mental/spiritual. Dualism necessarily introduces the mind-body problem: how to explain the interface between the body and the mind.
Descartes believed that the mind permeated the whole body yet felt compelled to identify its physical axis: finally settling on the pineal gland as the organ through which the mind exerted its effects on the body. It helped that the pineal gland was surrounded by animal spirits (now known as cerebrospinal fluid).
As to how the ethereal mind influenced the physical body, Descartes offered several stories until, dissatisfied, he confessed himself flummoxed for a logical explanation. This supposedly supreme rationalist philosopher was reduced to pleading common sense.
Despite his extensive sophistry Descartes had lasting influence. Most significantly, by rendering subjective experience respectable (again) he opened the door to the study of mind.
Descartes’ work on animal-versus-human and rational-versus-irrational behavior sparked abiding interest. These were the same subjects that Freud later studied.
Some philosophers after Descartes were drawn to his mechanistic paradigm. Others stressed the cognitive side of Descartes’ philosophy, proclaiming the mind as the most important aspect of being human (it being axiomatic that humans are uniquely superior). In either instance, what followed Descartes was a reaction to him. For this reason, Descartes is often considered the father of modern philosophy in general, and of modern psychology particularly.
