The hardest thing to understand in the world is the income tax.

The only thing we can be certain of in this life is that we can be certain of nothing.

One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike -- and yet it is the most precious thing we have.

The last thing to collapse is the surface.

Few people are capable of expressing with equanimity opinions which differ from the prejudices of their social environment. Most people are even incapable of forming such opinions.

There is no logical way to the discovery of these elemental laws. There is only the way of intuition, which is helped by a feeling for the order lying behind the appearance.

The heart says yes, but the mind says no.