There are in fact two things, science and opinion; the former begets knowledge, the latter ignorance.

It is always advisable to perceive clearly our ignorance.

When you know a thing, to hold that you know it; and when you do not know a thing. To allow that you do not know it—this is knowledge.

Knowledge rests not upon truth alone, but upon error also.

The possession of knowledge does not kill the sense of wonder and mystery. There is always more mystery.

There is nothing so absurd or ridiculous that has not at some time been said by some philosopher.

There is a wisdom in this beyond the rules of physic. A man’s own observation, what he finds good of and what he finds hurt of, is the best physic to preserve health.

No one can draw more out of things, books included, than he already knows. A man has no ears for that to which experience has given him no access.

The opinion of 10,000 men is of no value if none of them know anything about the subject.