A little cooling down of animal excitability and instinct, a little loss of animal toughness, a little irritable weakness and descent of the pain-threshold, will bring the worm at the core of all our usual springs of delight into full view, and turn us into melancholy metaphysicians.

A metaphysician is one who, when you remark that twice two makes four, demands to know what you mean by twice, what by two, what by makes, and what by four. For asking such questions metaphysicians are supported in oriental luxury in the universities, and respected as educated and intelligent men.

That's metaphysics, my dear fellow. It's forbidden me by my doctor, my stomach won't take it.

Metaphysics is a restaurant where they give you a thirty thousand page menu, and no food.

When he to whom a person speaks does not understand, and he who speaks does not understand himself, that is metaphysics.