G.K. Chesterton on Defining Terms
Charles Dickens: A Critical Study (Dodd, Mead & Company: 1906) p. 1.
Much of our modern difficulty, in religion and other things, arises merely from this, that we confuse the word "indefinable" with the word "vague." If some one speaks of a spiritual fact as "indefinable" we promptly picture something misty, a cloud with indeterminate edges. But this is an error even in common-place logic. The thing that cannot be defined is the first thing; the primary fact. It is our arms and legs, our pots and pans, that are indefinable. The indefinable is the indisputable. The man next door is indefinable, because he is too actual to be defined. And there are some to whom spiritual things have the same fierce and practical proximity; some to whom God is too actual to be defined.