Although this may seem a paradox, all exact science is dominated by the idea of approximation. When a man tells you that he knows the exact truth about anything, you are safe in inferring that he is an inexact man. Every careful measurement in science is always given with the probable error ... every observer admits that he is likely wrong, and knows about how much wrong he is likely to be.

When one admits that nothing is certain one must, I think, also admit that some things are much more nearly certain than others.

Right conduct can never, except by some rare accident, be promoted by ignorance or hindered by knowledge.

Change is scientific; progress is ethical; change is indubitable, whereas progress is a matter of controversy.

The theoretical understanding of the world, which is the aim of philosophy, is not a matter of great practical importance to animals, or to savages, or even to most civilised men.

What's the difference between a bright, inquisitive five-year-old, and a dull, stupid nineteen-year-old? Fourteen years of the British educational system.

The psychology of adultery has been falsified by conventional morals, which assume, in monogamous countries, that attraction to one person cannot coexist with affection for another. Everybody knows that this is untrue.