It is sufficient for our present purpose to state, that whatever occupies a distinct portion of space, however arbitrarily distinguished, is an individual object of external intuition; and whatever occupies a distinct moment of time, without extension in space, is an individual object of internal intuition. On the other hand, general notions or concepts, as such, have no definite position in time or space; though, when realised in an individual act of thought, they must have a relation to the former, and may have to the latter.
The mental development of the deaf and dumb is effected by the substitution of a system of signs addressed to the eye or the hand, in the place of one addressed to the ear; and this system performs precisely the same office in relation to them that speech performs in relation to others: it constitutes, in fact, their language. Language in this sense appears, as far as experience can inform us, to be necessary, not merely to the communication, but even to the formation, of thought.
The notion, as such, must be emancipated from all special relation to space or time. The definition of a triangle must not imply where it exists; nor the definition of anger, when it takes place; and this emancipation is never completely effected, except by means of symbols, verbal or other, by which the notion is fixed as a relation in the understanding.
We have thus, in the complete exercise of thought, three successive representations. The sign is representative of the notion; the notion is representative of the image; and the image is representative of the object from which the notion was formed. Presentative and representative consciousness, thus distinguished, must be considered, in their actual exercise, as indicating a logical rather than a real division; as pointing out the elements of a perfect act of consciousness, which are separable in thought; but not two distinct acts existing separately in practice.
***Excerpt from Henry Longueville Mansel, B.d.. Metaphysics or the philosophy of consciousness