Je pense donc je suis - René Descartes

But as soon as I had finished my course of study, at which time it is usual to be admitted to the ranks of the well educated, I completely changed my opinion, for I found myself bogged down in so many doubts and errors, that it seemed to me that having set out to become learned, I had derived no benefit from my studies, other than that of progressively revealing to myself how ignorant I was.

But in my opinion, all things in nature occur mathematically.

while I wanted thus to think that everything was false, it necessarily had to be the case that I, who was thinking this, was something. And noticing that this truth — I think, therefore I am — was so firm and so assured that all the most extravagant suppositions of the skeptics were incapable of shaking it, I judged that I could accept it without scruple as the first principle of the philosophy I was seeking.