Descartes' Methodical Doubt: Path to Certainty

Descartes' Quest for Absolute Certainty

In the seventeenth century, rationalists and empiricists thus formulated a transcendental philosophical question: What are the limits of knowledge? From the rationalist point of view, deductive scientific developments that took place since the sixteenth century were especially important. René Descartes thus sought to achieve absolute certainty in the metaphysical field, just as mathematics offers irrefutable truths, such as "2 + 2 = 4" or "the square of the hypotenuse equals the sum of the squares of the other two sides."

To this end, Descartes undertook the path of methodical doubt. To achieve absolute certainty, one must begin by doubting. This doubt is universal, as it questions all previously held certainties, including philosophical ones (a clear allusion to medieval scholasticism). The doubt is not skeptical or stationary, as Descartes aimed to achieve absolute certainty. Its purpose is constructive: it is an instrument to reach the truth. Moreover, the doubt is purely theoretical, meaning it does not extend to matters of conduct and moral behavior.

The Procedure of Methodical Doubt

The procedure, then, consists of exposing the truths we trust and then examining if there is any reason to doubt them:

• Doubt of the Testimony of the Senses

  In principle, we rely on the senses, but we all know they can be misleading. We have no criterion by which to know when the senses deceive us and when not. Although it is unlikely that they are always deceiving, it is better not to trust those who deceive us even once. Therefore, the truth of empirical evidence is bracketed, as it cannot serve as unquestionable axioms.

• Doubt of Reality: Distinction of Wakefulness and Sleep

  Who says we are not dreaming when we think that what we hold is reality? Sometimes, says Descartes, it happens that in dreams we seem to be in a certain place and certain things happen to us; then, when we wake, we know them to be false. There seems to be no clear reason to distinguish between the state of sleep and waking. The consequence is that the existence of the external world and ourselves within it is questioned; perhaps all is merely the product of our dreams.

• Doubt of Mathematical Principles

  It is known that our reasoning can go wrong, even in mathematical elaborations. Could it be that an evil demon created us in such a way that we believe falsehoods to be true, without the possibility of realizing our error? Therefore, if even rational truths are questionable, we cannot rely on reason as a source of reliable knowledge for the foundational principles of philosophy.

The Certainty of the Thinking Subject

When it seems we are left with skepticism, having annihilated the two sources of knowledge—sense and reason—we can, however, affirm one great certainty: the act of thought and consciousness. I can doubt everything, but I cannot doubt that I am doubting. Thought and existence are perceived simultaneously.

In conclusion, we arrive at the absolute certainty of the existence of the thinking subject (Cogito, ergo sum), a truth clearly and distinctly manifested, without darkness or confusion.