Cartesian epistemological method

Through the epistemological turn, Descartes’ philosophical framework – his foundationalism, methodology, and philosophical assumptions – continues to influence and shape the contemporary philosophy of science.

Cartesian epistemology is best known for its method of universal doubt. Dissatisfied with his own education, as well as with the state of academic and philosophical debate, Descartes rejected all beliefs that were capable of being doubted, no matter how slightly. He likened his methodical doubt to tearing down an old, unstable house in order to uncover a firm foundation upon which to erect a new, improved dwelling. In his “Discourse on the Method,” he described how it is possible to doubt the senses, syllogistic logic, and even mathematics, revealing that which Descartes took to be his solid foundation.

For a long time I had observed, as noted above, that in practical life it is sometimes necessary to act upon opinions which one knows to be quite uncertain just as if they were indubitable. But since I now wished to devote myself solely to the search for truth, I thought it necessary to do the very opposite and reject as if absolutely false everything in which I could imagine the least doubt, in order to see if I was left believing anything that was entirely indubitable. This, because our senses sometimes deceive us, I decided to suppose that nothing was such as they led us to imagine. And since there are men who make mistakes in reasoning, committing logical fallacies concerning the simplest questions in geometry, and because I judged that I was as prone to error as anyone else, I rejected as unsound all the arguments I had previously taken as demonstrative proofs. Lastly, considering that the very thoughts we have while awake may also occur while we sleep without any of them being at the that time true, I resolved to pretend that all the things that had ever entered my mind were no more true than the illusions of my dreams. But immediately I noticed that while I was trying thus to think everything false, it was necessary that I, who was thinking this, was something. And observing that this truth ‘I am thinking, therefore I exist’ was so firm and sure that all the most extravagant suppositions of the sceptics were incapable of shaking it, I decided that I could accept it without scruple as the first principle of the philosophy I was seeking. (1)

But why did he seek to refound philosophy in this manner? More specifically, what considerations lead him to construct a new philosophy, initiated through the universal doubt of all beliefs? Further, how did he envision resolving the radical doubt in order to provide him with the certitude he sought?

For Descartes the only knowledge worthy of the name scientia was certain, self-evident knowledge. This understanding of knowledge was precisely what was absent from the philosophy of his day. Moreover, no other discipline was secure as long as the foundations of philosophy remained shaky and unstable. In order to vouchsafe all human knowledge, the confusion at the root of philosophy must be clarified. Universal doubt would allow him uncover these indubitable beliefs that would serve as the new basis for his philosophy, which he supposed he found in the cogito. But how would he rebuild from here?

Having spent years studying logic, geometrical analysis, and algebra, Descartes modeled his epistemic method upon the certainty and clarity which resulted from the methods of mathematics. He had delighted in the simplicity and precision of the incremental steps that unfolded in each mathematical demonstration since his time at the Sorbonne. But while logic, geometrical analysis, and algebra each had their strengths, they also each had their own proper applications. This would require him to generalize each of those disciplines “to seek some other method comprising the advantages of these three subjects but free from their defects (2).”

In “Rules for the Direction of the Mind”, he called this ‘universal method’. His general mathematical method was composed of only two cognitive activities, intuition and deduction. By intuition, Descartes meant the immediate perception of clear ideas by an attentive mind. Moreover, he referred to intuition as “the indubitable conception of a clear and attentive mind which proceeds solely from the light of reason (3).” In his later writings, he would drop explicit reference to intuition as one of two cognitive activities and refer simply to his clear and distinct ideas.

By deduction, Descartes meant “the inference of something as following necessarily from some other propositions which are known with certainty (4).” The propositions “known with certainty” are those known by intuition, or known clearly and distinctly. However, deduction must be added to intuition “since very many facts which are not self-evident are known with certainty, provided they are inferred from true and known principles through a continuous and uninterrupted movement of thought in which each individual proposition is clearly intuited (5).” Deduction, then, is something like the awareness of the movement through successive and connected instances of intuition. An initial intuition that begins such a chain of reasoning might be considered a self-evident first principle and one might conclude that other clear and distinct propositions necessarily follow from this basic intuition, thereby inheriting the basic intuitions’ indubitability. The tracing of this necessity and the preservation of this indubitability from one proposition, or intuition, to the next is deduction for Descartes.

To sum up, Cartesian epistemological method first employs universal doubt to jettison all potentially dubious beliefs in order to uncover self-evident, indubitable ideas, which are perceived through intuition. Second, through a process of careful deduction, other ideas are derived from self-evident and indubitable ones. This amounts to a foundationalist strategy modeled upon the core principle of mathematical demonstrations, namely deduction.

Kim concludes, and I think rightly so, that the core of Cartesian epistemology, which instituted an entirely new tradition of epistemic and philosophical inquiry, has two central goals:

We can view Cartesian epistemology as consisting of the following two projects: to identify the criteria by which we ought to regulate acceptance and rejection of beliefs, and to determine what we may be said to know according to those criteria. Descartes’ epistemological agenda has been the agenda of Western epistemology to this day. The twin problems of identifying criteria of justified belief and coming to terms with the skeptical challenge to the possibility of knowledge have defined the central tasks of theory of knowledge since Descartes. This was as true of empiricists, of Locke and Hume and Mill, as of those who more closely followed Descartes in the rationalist path. (6)

Notes

1. Descartes, “Discourse on the Method,” p. 126 – 7.
2. ibid., p. 120.
3. Descartes, “Rules for the Direction of the Mind,” p. 14.
4. ibid., p. 15.
5. ibid., p. 15.
6. Kim, “What is ‘Naturalized Epistemology’?,” p. 381.