Summary: Meditations on First Philosophy

Is there any truth that is absolutely certain?

It is to this question that Descartes seeks an answer in the Meditations on First Philosophy.

Descartes remarks that the senses deceive us, and that for this reason it is prudent not to trust those who have once deceived us.

He takes up the sceptical arguments: a square tower appears round from a distance, a stick dipped in water appears broken, etc.

Certainly, doubting the existence or truth of the outside world seems extravagant. However, we must not forget that when we dream, we firmly believe in the reality of what we see in our dreams, when it is really just an illusion. Would we be living in a dream, in which nothing really exists?

Descartes replies that imagination has its limits: it cannot create new things, merely combine them differently. So it probably could not have created our world on its own.

Descartes proposes a distinction between the science of compound things (physics, medicine) which would be doubtful, because working on things that the imagination could have forged by fanciful combinations, and the science of simple things (arithmetic, geometry, etc.) working on extent, figures, quantities, place, time, and which would themselves be certain. For whether I am awake or asleep, two and three joined together will always form the number five ¹.

However, the author of the Meditations on First Philosophy himself brushes aside this distinction: perhaps God deceives us even on this. Does not God's goodness exclude this hypothesis? How could he deceive us in this way?

In fact, the very existence of God is uncertain. We are therefore, once again, in deep uncertainty.

Descartes then imagines the most pessimistic hypothesis possible, that of the evil demon:

A certain evil demon, no less cunning and deceitful than powerful has employed all his industry in deceiving me ².

This hypothesis, which closes Book I, is taken up again at the beginning of Book II. Descartes is still searching for an indubitable truth, like Archimedes who demanded a fixed point to lift the earth.

In fact, at the very heart of the most pessimistic hypothesis, that of the evil demon, lies a certain truth: There is therefore no doubt that I am, if he deceives me ³.

So we see appearing here what is called the Cartesian cogito:

So that, having thought it through, we must conclude and hold it to be constant that this proposition: I am, I exist is necessarily true whenever I utter it or conceive it in my mind ⁴.

In the Discourse on Method, Descartes summed this up more elliptically: I think, therefore I am.

At the very heart of doubt, then, lies a certain truth. Does it conceal others?

Descartes attempts to discover other indubitable truths from it.

Can we, first of all, say anything certain about this thinking self? What is the " I" of the "I think"?

Am I a man? Am I a soul? All these vague terms cannot be retained: what is a man? A reasonable animal, as defined by Aristotle and the scholastics? What is a soul? Wouldn't I be more than just a soul, also a body?

In fact, we must return to the indubitable truth of "I think". All that can be said with certainty about myself is that I am, precisely speaking, only a thing that thinks ⁵.

We can therefore also admit a quantity of other truths about the self, starting from this essential attribute, thinking, which defines the self:

What is a thing that thinks? It is a thing that doubts, hears, conceives, affirms, denies, wills, does not will, also imagines, and feels ⁶.

Thus from the cogito, little by little, we deduce a quantity of certain truths.

¹ Méditations métaphysiques, GF Flammarion, Paris, 2009, p.85
² p.89
³ Ibid.
⁴ Ibid.
⁵ p.97
⁶ p.99