Everything excellent is as difficult as it is rare.

Anyone who seeks for the true causes of miracles, and strives to understand natural phenomena as an intelligent being, and not to gaze at them like a fool, is set down and denounced as an impious heretic.

Those who wish to seek out the cause of miracles and to understand the things of nature as philosophers, and not to stare at them in astonishment like fools, are soon considered heretical and impious, and proclaimed as such by those whom the mob adores as the interpreters of nature and the gods.

I can control my passions and emotions if I can understand their nature

The more intelligible a thing is, the more easily it is retained in the memory, and counterwise, the less intelligible it is, the more easily we forget it.

Freedom is absolutely necessary for the progress in science and the liberal arts.

Things could not have been brought into being by God in any manner or in any order different from that which has in fact obtained.