Love should be a tree whose roots are deep in the earth, but whose branches extend into heaven.

Aristotle could have avoided the mistake of thinking that women have fewer teeth than men, by the simple device of asking Mrs. Aristotle to keep her mouth open while he counted.

I have found, for example, that if I have to write upon sum rather difficult topic, the best plan is to think about it with very great intensity-the greatest intensity of which I am capable-for a few hours or days, and at the end of that time give orders, so to speak (to my subconscious mind) that the work is to proceed underground. After some months I return consciously to the topic and find that the work has been done.

My doctor said to me afterwards, 'When you were ill you behaved like a true philosopher. Every time you came to yourself you made a joke.' I never had a compliment that pleased me more.

An educator should think of a child as a gardener thinks of a plant, as something to be made to grow by having the right soil and the right amount of water. If your roses fail to bloom, it does not occur to you to whip them, but you try to find out what has been amiss in your treatment of them. ... The important thing is what the children do, and not what they do not do. And what they do, if it is to have value, must be a spontaneous expression of their own vital energy.

Man is a rational animal – so at least I have been told. Throughout a long life, I have looked diligently for evidence in favour of this statement, but so far I have not had the good fortune to come across it, though I have searched in many countries spread over three continents.

It is not by delusion, however exalted, that mankind can prosper, but only by unswerving courage in the pursuit of truth.