“Having wandered some distance among gloomy rocks, I came to the entrance of a great cavern ... Two contrary emotions arose in me: fear and desire--fear of the threatening dark cavern, desire to see whether there were any marvelous things in it.”

“Learning is the only thing the mind never exhausts, never fears, and never regrets.”

“Study without desire spoils the memory, and it retains nothing that it takes in.”

“Experience is never at fault; it is only your judgment that is in error, in promising itself such results from experience as are not caused by our experiments. For having given a beginning, what follows from it must necessarily be a natural development of such a beginning, unless it has been subject to a contrary influence, while, if it is affected by any contrary influence, the result which ought to follow from the aforesaid beginning, will be found to partake of this contrary influence in a greater or lesser degree in proportion as the said influence is more or less powerful than the aforesaid beginning.”

“Every now and then go away, have a little relaxation, for when you come back to your work your judgment will be surer. Go some distance away because then the work appears smaller and more of it can be taken in at a glance and a lack of harmony and proportion is more readily seen.”

“We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.”

“A painter should begin every canvas with a wash of black, because all things in nature are dark except where exposed by the light.”