Putting the shoe on the wrong foot.

The soul of him who has education is whole and perfect and escapes the worst disease, but, if a man's education be neglected, he walks lamely through life and returns good for nothing to the world below.

The ludicrous state of solid geometry made me pass over this branch.

There is a ... matter - much more valuable and divine than natural philosophy . ... On this matter I must speak to you in enigmas.

Love is a grave mental illness.

Wisdom alone is the science of others sciences.

When the mind is thinking it is talking to itself.