Rene Descartes

Selections from the Principles of Philosophy Rene Descartes

I. THAT in order to seek truth, it is necessary once in the course of our life, to doubt, as far as possible, of all things. As we were at one time children, and as we formed various judgments regarding the objects presented to our senses, when as yet we had not the entire use of our reason, numerous prejudices stand in the way of our arriving at the knowledge of truth; and of these it seems impossible for us to rid ourselves, unless we undertake, once in our lifetime, to doubt of all those things in which we may discover even the smallest suspicion of uncertainty.