The interaction of knowledge and skills with experience is key to learning.

A book or a letter may institute a more intimate association between human beings separated thousands of miles from each other than exists between dwellers under the same roof.

In general, every stimulus directs activity. It does not simply excite it or stir it up, but directs it toward an object.

Intelligence is in constant process of forming, and its retention requires constant alertness in observing consequences, an open-minded will to learn, and courage in readjustment.

If we learn not humility, we learn nothing.

Man is merely a frequent effect, a monstrosity is a rare one, but both are equally natural, equally inevitable, equally part of the universal and general order. And what is strange about that? All creatures are involved in the life of all others, consequently every species... all nature is in a perpetual state of flux. Every animal is more or less a human being, every mineral more or less a plant, every plant more or less an animal... There is nothing clearly defined in nature.

It has been petrified into a slavery of thought and sentiment, as intolerant superiority on the part of the few and an intolerable burden on the part of the many.