As the biggest library if it is in disorder is not as useful as a small but well-arranged one, so you may accumulate a vast amount of knowledge but it will be of far less value to you than a much smaller amount if you have not thought it over for yourself; because only through ordering what you know by comparing every truth with every other truth can you take complete possession of your knowledge and get it into your power. You can think about only what you know, so you ought to learn something; on the other hand, you can know only what you have thought about.
As a general rule, the longer a man's fame is likely to last, the later it will be in coming; for all excellent products require time for their development.
Of all the intellectual faculties, judgment is the last to mature. A child under the age of fifteen should confine its attention either to subjects like mathematics, in which errors of judgment are impossible, or to subjects in which they are not very dangerous, like languages, natural science, history, etc.
It is most important to allow the brain the full measure of sleep which is required to restore it; for sleep is to a man's whole nature what winding up is to a clock.
Whoever wants his judgment to be believed, should express it coolly and dispassionately; for all vehemence springs from the will. And so the judgment might be attributed to the will and not to knowledge, which by its nature is cold.