We began with the bare unit, or simple and unanalysed point, which satisfied popular language and popular imagination as its _nucleus_:--the representation which had caught and half-idealised a point, moment, or aspect in the range of feeling and sensation. In this stage the notion or thought proper is yet latent. In the first place, the _nucleus_ of imagination was analysed, defined, and, as we may surmise, narrowed in the Intellect. And this grade of thought is known as the Understanding. In the second place, the definite and precise term, as understanding supposes it, was subjected to criticism: its contradictions displayed; and the very opposite of the first definition established in its place. This is the action of Dialectic. In the third place, by means of this second stage, the real nature or truth was seen to lie in a union where the opposites interpenetrate and mould each other. Thus we have as a conscious unity,--conscious because it, as unity, yet embraces a difference as difference--what we started with as an unconscious unity, the truth of feeling, faith, and inspiration. The first was an immediate unity:--that is to say, we were in the midst of the unity, sunk in it, and making a part of it: the second is a mediated unity, which has been reached by a process of reflection, and which as a conscious unity involves that process. Reason, then, is infinite, as opposed to understanding, which is finite thinking. The limits which are found and accepted by the analytic intellect, are limits which reason has imposed, and which it can take away: the limits are in it, and not over it. The larger reason has been laying down those limits, which our little minds at first tend to suppose absolute. Let us put the same law in more concrete terms. It is reason,--the Idea,--or, to give it an inadequate and abstract name, Natural Selection--which has created the several forms of the animal and vegetable world: it is reason, again, which in the struggle for existence contradicts the very inadequacies which it has brought into being: and it is reason, finally, which affirms both these actions,--the hereditary descent, and the adaptation--in the provisionally permanent and adequate forms which result from the struggle.