This is all taken from an essay entitled "Eugenics and Other Evils"
"Suppose we are all standing round a field and looking at a tree in the middle of it. It is perfectly true that we all see it in infinitely different aspects: that is not the point; the point is that we all say it is a tree. Suppose we are all poets... a conservative poet may wish to clip the tree; a revolutionary poet may wish to burn it. An optimist poet may want to make it a Christmas tree and hang candles on it. A pessimist poet may want to hang himself on it. None of these are mad, because they are all talking about the same thing. But there is another man who is talking horribly about something else. There is a monstrous exception to mankind. Why he is so we know not; a new theory says it is heredity; an older theory says it is devils. But in any case, the spirit of it is the spirit that denies, the spirit that really denies realities. This is the man who looks at the tree and...says it is a lamp-post...the difference between us and the maniac is not about how things look or how things ought to look, but about what they self-evidently are."
As G.K. is noting (Sartre, Nietzsche, Foucault... are you listening?) words mean things, reality is real.