syntheses, are reals in a mind; and the mind must not merely, as it were, flow around them, but have them fluid members of itself. If they are reals, they are ideal-reals. You must begin with an ideal-unity which is also a real-unity, in which variety can play and by which it is controlled. 'Forces,' no less than 'things,' are terms of thought, names of reality indeed, but inadequate because due to an abstraction and leaving their correlatives out of sight--names of momentary elements seized in the flux, and made with more or less success to indicate 'moments' and 'factors' or 'aspects' in the total sum and power of reality. Explanation by permanent and separate forces labours under the same disadvantages as that by things. Science, grown more self-critical, begins to see that in forces, &c., it has names and formulae which are not the full reality, but only useful (_if_ useful) abstractions. Neither things nor forces, though called real, are so in the full sense. Hume said,--and said not untruly, though with some relish of paradox,--that we never had any real impression or idea of power and force. The statement should be taken along with another that what we mistake for power in things is only our own want of power to overcome a suggested association, or to break a customary train of ideas. Lotze, again, has remarked that the supposed consciousness of power exerted in voluntary movement is confused with a feeling of work done, or inertia overcome. Whatever may be the truth about the psychological experience, there can be no doubt for the epistemologist that the so-called perception of force is an interpretation of one aspect of experience which, with a certain amount of arbitrary arrest and simplification, renders it intelligible and real by means of an antithesis and correlation. Force in fact only exists, or arises, in relation or opposition to a counter-force: action and re-action are always equal and opposite, says the mathematical formula. Two forces are as little independent as an up and a down, or as a west and a north; force solicits force, and force only _is_ in so far as it is solicited. The soliciting can only solicit because it is solicited. In other words, it is not enough to say that the forces which thus confront each other are correlatives. The relationship must be carried up a stage higher: the forces themselves get their pseudo-real character, only so long as they are kept apart forcibly or by inertia. Carry out their implications: and they re-unite (not however to the loss of all distinction) in a higher idea, an intelligible unity which, by its division and return to unity, makes possible and real their contention. It is this carrying-out of implications to their explicit truth which is at the root of Schopenhauer's playing fast and loose with the distinction between force and will. But with him the two terms are taken up vague and indefinite, in the haze of popular conception or