Suppose, for the sake of argument, that I say that to take away a poor man’s pot of beer is to take away a poor man’s personal liberty, it is very vital to note what is the usual or almost universal reply. People hardly ever do reply, for some reason or other, by saying that a man’s liberty consists of such and such things, but that beer is an exception that cannot be classed among them, for such and such reasons. What they almost in variably do say is something like this. “After all, what is liberty? Man must live as a member of a society, and must obey those laws which, etc., etc.” In other words, they collapse into a complete confession that they are attacking all liberty and any liberty; that they do deny the very existence or the very possibility of liberty. In the very form of the answer they admit the full scope of the accusation against them. In trying to rebut the smaller accusation, they plead guilty to the larger one.
This distinction is very important, as can be seen from any practical parallel. Suppose we wake up in the middle of the night and find that a neighbor has entered the house not by the front-door but by the skylight; we may suspect that he has come after the fine old family jewellery. We may be reassured if he can refer it to a really exceptional event; as that he fell on to the roof out of an aeroplane, or climbed on to the roof to escape from a mad dog. Short of the incredible, the stranger the story the better the excuse; for an extraordinary event requires an extraordinary excuse. But we shall hardly be reassured if he merely gazes at us in a dreamy and wistful fashion and says, “After all, what is property? Why should material objects be thus artificially attached, etc., etc.?” We shall merely realize that his attitude allows of his taking the jewellery and everything else. Or if the neighbour approaches us carrying a large knife dripping with blood, we may be convinced by his story that he killed another neighbour in self-defence, that the quiet gentleman next door was really a homicidal maniac. We shall know that homicidal mania is exceptional and that we ourselves are so happy as not to suffer from it, and being free from the disease may be free from the danger. But it will not soothe us for the man with the gory knife to say softly and pensively, “After all, what is human life? Why should we cling to it? Brief at the best, sad at the brightest, it is itself but a disease from which, etc., etc.” We shall perceive that the sceptic is in a mood not only to murder us but to massacre everybody in the street.
Exactly the same effect which would be produced by the questions of “What is property?” and “What is life?” is produced by the question of “What is liberty?” It leaves the questioner free to disregard any liberty, or in other words to take any liberties. The very thing he says is an anticipatory excuse for anything he may choose to do. If he gags a man to prevent him from indulging in profane swearing, or locks him in the coal cellar to guard against his going on the spree, he can still be satisfied with saying “After all, what is liberty? Man is a member of, etc., etc.”
— Eugenics and Other Evils (1922).