 La Forge argued that, in addition to understanding and willing, the human mind must have an intellectual memory; since it can reason about purely spiritual realities, and since reasoning involves moving from one step to another and remembering those on which one relies for progress, the human mind must be capable of remembering purely spiritual concepts of which it has had no corresponding corporeal species (T 291; THM 187). La Forge concludes in Chapter xxv that the human mind is immortal; since its essence is to think, the mind continues to think constantly for eternity and may also remember things that do not presuppose the presence of a body.