It must be remembered, that what we call exertion, in our bodily operations, is nothing more, as we have seen, than the subsequence of muscular motion to the feeling which we denominate desire or will; as magnetic action, in a process purely material, is the subsequence of the motion of iron to the approach of a loadstone.1818, Thomas Brown, Inquiry into the Relation of Cause and Effect, third edition, page 83: