In God there is an infinitude of things which I cannot comprehend, nor possibly even reach in any way by thought; for it is the nature of the infinite that my nature, which is finite and limited, should not comprehend it.

...it is certain that I am really distinct from my body, and can exist without it.

This result could have been achieved either by his [God] endowing my intellect with a clear and distinct perception of everything about which I would ever deliberate, or simply by impressing the following rule so firmly upon my memory that I could never forget it: I should never judge anything that I do not clearly and distinctly understand.

I suppose therefore that all things I see are illusions; I believe that nothing has ever existed of everything my lying memory tells me. I think I have no senses. I believe that body, shape, extension, motion, location are functions. What is there then that can be taken as true? Perhaps only this one thing, that nothing at all is certain.

Give me extension and motion and I will construct the universe.

How can you be certain that your whole life is not a dream?

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.