I have already said that a thing which 'exists in a person's head' and nowhere else is alternatively called an imaginary thing. The actual making of … - R. G. Collingwood

a) The definition of history?' Every historian would agree, I think, that history is a kind of research or inquiry. What kind of inquiry it is I do not yet ask. The point is that generically it belongs to what we call the sciences: that is, the forms of thought whereby we ask questions and try to answer them. Science in general, it is important to realize, does not consist in collecting what we already know and arranging it in this or that kind of pattern. It consists in fastening upon something we do not know, and trying to discover it. Playing patience with things we already know may be a useful means towards this end, but it is not the end itself. It is at best only the means. It is scientifically valuable only in so far as the new arrangement gives us the answer to a question we have already decided to ask. That is why all science begins from the knowledge of our own ignorance: not our ignorance of everything, but our ignorance of some definite thing-the origin of parliament, the cause of cancer, the chemical composition of the sun, the way to make a pump work without muscular exertion on the part of a man or a horse or some other docile animal. Science is finding things out: and in that sense history is a science.

We can now return to the distinction between language and symbolism. A symbol is language and yet not language. A mathematical or logical or any other kind of symbol is invented to serve a purpose purely scientific; it is supposed to have no emotional expressiveness whatever. But when once a particular symbolism has been taken into use and mastered, it reacquires the emotional expressiveness of language proper. Every mathematician knows this. At the same time, the emotions which mathematicians find expressed in their symbols are not emotions in general, they are the peculiar emotions belonging to mathematical thinking.

Rational truth — and all truth is rational — is essentially that which can justify itself under criticism and in discussion.