Simultaneous discovery is utterly commonplace, and it was only the rarity of scientists, not the inherent improbability of the phenomenon, that made it remarkable in the past. Scientists on the same road may be expected to arrive at the same destination, often not far apart.

Twice in my life I have spent two weary and scientifically profitless years seeking evidence to corroborate dearly loved hypotheses that later proved to be groundless; times such as these are hard for scientists-days of leaden gray skies bringing with them a miserable sense of oppression and inadequacy.

If a scientist were to cut his ear off, no one would take it as evidence of a heightened sensibility.

The bells which toll for mankind are - most of them, anyway - like the bells of Alpine cattle; they are attached to our own necks, and it must be our fault if they do not make a cheerful and harmonious sound.

It goes with the passionate intensity and deep conviction of the truth of a religious belief, and of course of the importance of the superstitious observances that go with it, that we should want others to share it - and the only certain way to cause a religious belief to be held by everyone is to liquidate nonbelievers. The price in blood and tears that mankind generally has had to pay for the comfort and spiritual refreshment that religion has brought to a few has been too great to justify our entrusting moral accountancy to religious belief.

For a scientist must indeed be freely imaginative and yet skeptical, creative and yet a critic. There is a sense in which he must be free, but another in which his thought must be very preceisely regimented; there is poetry in science, but also a lot of bookkeeping.

It is a common failing-and one that I have myself suffered from-to fall in love with a hypothesis and to be unwilling to take no for an answer. A love affair with a pet hypothesis can waste years of precious time. There is very often no finally decisive yes, though quite often there can be a decisive no.