“So my antagonist said, "Is it impossible that there are flying saucers? Can you prove that it's impossible?" "No", I said, "I can't prove it's impossible. It's just very unlikely". At that he said, "You are very unscientific. If you can't prove it impossible then how can you say that it's unlikely?" But that is the way that is scientific. It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible.”

“All things are possible until they are proved impossible and even the impossible may only be so, as of now.”

“Often-times it's madness, not genius that moves the world forward. Who else but the mad would reach so far, stretching for the impossible and, in so doing, prove the impossible possible!”

“It's not the cost (although that pinches), or the time (though that grinds). After a while, it's the sheer galling indignity of being asked to prove, pay, and prove all over again that you're a worthy parent. Any true parent will tell you that that is impossible to prove in advance.”

“Surrealism also refuses the representation of reality: reality can only be; its existence proves its reality. Fiction thereby becomes impossible or is, by definition, false.”

“What the hell does liberty mean anyhow? It's just a word like house or table or any other word. Only it's a special kind of word. A guy says house and he can point to a house to prove it. But a guy says come on let's fight for liberty and he can't show you liberty. He can't prove the thing he is talking about so how in the hell can he be telling you to fight for it?”