All is to be doubted.

There is a great difference between mind and body insomuch as body is by nature always divisible, and the mind is entirely indivisible.

De omnibus dubitandum

I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake.

If ... it is not in my power to arrive at the knowledge of any truth, I may at least do what is in my power, namely, suspend judgement.

So blind is the curiosity by which mortals are possessed, that they often conduct their minds along unexplored routes, having no reason to hope for success, but merely being willing to risk the experiment of finding whether the truth they seek lies there.

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