The rainbow is such a remarkable phenomenon of nature, and its cause has been so meticulously sought after by inquiring minds throughout the ages, that I could not choose a more appropriate subject for demonstrating how, with the method I am using, we can arrive at knowledge not possessed at all by those whose writings are available to us.

Instead I ought to be grateful to Him who never owed me anything for having been so generous to me, rather than think that He deprived me of those things or has taken away from me whatever He did not give me.

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.

And as it is the most generous souls who have most gratitude, it is those who have most pride, and who are most base and infirm, who most allow themselves to be carried away by anger and hatred.

Doubt is the origin of wisdom

It is not enough to have a good mind. The main thing is to use it well.

Science is practical philosophy.