What Plato was really asking was perhaps why a horse was a horse, and not, for example, a cross between a horse and a pig.
Jostein GaarderSocrates himself said, 'One thing only I know, and this is that I know nothing.' Remember this statement, because it is an admission that is rare, even among philosophers. Moreover, it can be so dangerous to say in public that it can cost you your life. The most subversive people are those who ask questions. Giving answers is not nearly as threatening. Any one question can be more explosive than a thousand answers.
Jostein GaarderAnd although I have seen nothing but black crows in my life, it doesn't mean that there's no such thing as a white crow. Both for a philosopher and for a scientist it can be important not to reject the possibility of finding a white crow. You might almost say that hunting for 'the white crow' is science's principal task.
Jostein Gaarder