The practical activity, the will, which is also strife between good and evil, can be illuminated now from this side and now from that by that indivisible unity, according to the accidents of discourse and the varying situations of life. In this way arises a series of concepts which, in so far as they are unilateral, are empirical, and only become again philosophical in the thought of the unity of which they form part. Thus, to make use of a comparison, space in geometry can be analyzed and split up into a first, second, and third dimension; but as spatiality, it is a _unicum,_ which does not possess either one or two or three dimensions; and when in measuring or constructing plans of measurement, we proceed to think one of these dimensions, we become aware that we cannot think them, save all three together, or not as three, but as one. The empirical, practical concepts that arise upon the antithetical and dialectical nature of the will, have had much importance, and it is fitting, therefore, that we should mention and explain at least the principal among them. [Sidenote: _Duty of being, ideal, inhibitive, and imperative power._] If the situations of life lead to the directing of the attention chiefly to the aspect of the will striving against inaction and arbitrary choice, it is posited in this strife, in this becoming, as something that _is not_ but _must be,_ not as _real,_ but as _ideal._ If the greatness of the ideal that is to be and to fill the soul with joy, be set in relief in this struggle, then the ideal appears sweet and smiling, as a _joy-bringing and beatific vision._ If, on the other hand, the effort of its becoming be set in relief, the ideal can be made into a metaphor, as will opposed to will, as legitimate against rebellious will; and then it assumes a sour, rough, and hard appearance, and the names of _inhibitive or imperative power,_ in so far as it impedes the will, or promotes liberty.