I have never seen the slightest scientific proof of the religious ideas of heaven and hell, of future life for individuals, or of a personal God.

I am afraid of radium and polonium ... I don't want to monkey with them.

I have not failed. I've just found 10,000 foundations and individual donors whose priorities don't align with my organization's.

I have far more respect for the person with a single idea who gets there than for the person with a thousand ideas who does nothing.

Large portions of life's disappointments are individuals who did not understand that they were so near achievement when they surrendered.

The value of an idea lies in the using of it.

It is astonishing what an effort it seems to be for many people to put their brains definitely and systematically to work.