- The criterion which we use to test the genuineness of apparent statements of fact is the criterion of verifiability. We say that a sentence is factually significant to any given person, if, and only if, he knows how to verify the proposition which it purports to express - that is, if he knows what observations would lead him, under certain conditions, to accept the proposition as being true, or reject it as being false.
- If now I:say 'Stealing money is wrong,' I produce a sentence which has no factual meaning - that is, expresses no proposition which can be either true or false. It is as if I had written 'Stealing money!!' - where the shape and thickness of the exclamation marks show, by a suitable convention, that a special sort of moral disapproval is the feeling which is being expressed.
- No moral system can rest solely on authority.
- There never comes a point where a theory can be said to be true. The most that one can claim for any theory is that it has shared the successes of all its rivals and that it has passed at least one test which they have failed.
- It seems that I have spent my entire time trying to make life more rational and that it was all wasted effort.