It must not be thought that it is ever possible to reach the interior earth by any perseverance in mining: both because the exterior earth is too thick, in comparison with human strength; and especially because of the intermediate waters, which would gush forth with greater impetus, the deeper the place in which their veins were first opened; and which would drown all miners.

You just keep pushing. You just keep pushing. I made every mistake that could be made. But I just kept pushing.

Even if I were to suppose that I was dreaming and whatever I saw or imagined was false, yet I could not deny that ideas were truly in my mind.

I am thinking, therefore I exist. (...) I was a substance whose whole essence or nature is solely to think, and which does not require any place, or depend on any material thing, in order to exist. Accordingly this 'I' - that is, the soul by which I am what I am - is entirely distinct from the body, and indeed is easier to know than the body, and would not fail to be whatever it is, even if the body did not exist.

The first precept was never to accept a thing as true until I knew it as such without a single doubt.

I am indeed amazed when I consider how weak my mind is and how prone to error.

All is to be doubted.