Comprehension. This term is used in logic to denote the aggregate of qualities, the counter term extension denoting the number of objects, contained in a notion. Thought necessarily proceeds in these two directions. When I proceed in the latter I refer the perceived object to its species A, and that to its genus B, of each of which it is in that regard a part; but when I proceed in the former direction, that of comprehension, I view A and B as parts of the object. In respect of extension, B contains A, and A the object. In respect of comprehension, A contains B, and the object contains both.
The term comprehension labours under this disadvantage, that it would be quite natural to use it for extension, and Archbishop Whately actually does so. Accordingly it has been proposed to substitute for it the word intension. The two counter-wholes have likewise been denoted by the terms breadth and depth, the generic extension giving us the former, the qualities comprised in the object giving us the latter. In spite of all this, however, the names comprehension and extension hold their ground.
