What we makes of the world must be largely dependent on the sense-organs that we happen to possess. How the world must have changed since the man came to rely on his eyes rather than his nose.

Observation and theory get on best when they are mixed together, both helping one another in the pursuit of truth. It is a good rule not to put overmuch confidence in a theory until it has been confirmed by observation. I hope I shall not shock the experimental physicists too much if I add that it is also a good rule not to put overmuch confidence in the observational results that are put forward until they have been confirmed by theory.

If I let my fingers wander idly over the keys of a typewriter it might happen that my screed made an intelligible sentence. If an army of monkeys were strumming on typewriters they might write all the books in the British Museum. The chance of their doing so is decidedly more favourable than the chance of the molecules returning to one half of the vessel.

I don't believe any experiment until it is confirmed by theory. I find this is a witty inversion of "conventional" wisdom.

It is a primitive form of thought that things exist or do not exist.

If your theory is found to be against the second law of thermodynamics I give you no hope; there is nothing for it but to collapse in deepest humiliation.

The mathematics is not there till we put it there.