The present King of France is bald.

Is this statement true or false? Well, it’s not true — France has no king presently. But if it’s false then its negation ought to seem true: The present King of France is not bald. That’s no better. Yet it’s not gibberish — the sentence seems to have a clear meaning that we can understand.

Bertrand Russell and Alfred North Whitehead spent much of their time at Cambridge debating this point. “It is astonishing what intricate and remote considerations can be brought to bear on this interesting question,” Russell wrote to his wife. “We finally decided that he isn’t, altho’ he has no hair of his own. Experienced people will infer that he wears a wig, but this would be a mistake.”