The simultaneity, the inseparableness of the two mental acts or functions in regard to the same subject-matter is the essential point on which hangs the web of the argument here submitted. Thus in geometry space must be regarded as a continuum, unbroken, uninterrupted at any point, and at the same time the same space must be treated as capable of puncture, of linear and superficial delimitations; that is to say, of division. That which is one must yet be apprehended as divided; that which is divided, or delimitated, must yet be apprehended as one. The difficulties that arise spring from the vain endeavor to separate the two inseparable acts—the act of apprehending the manifold of space _sub specie pluralitatis_, and the act of apprehending it _sub specie unitatis_. Hence arises the puzzling question: How can that which is continuous be divided, how can chasms between the parts of space, however infinitesimal, be bridged? Witness the problem of Zeno, and the pragmatist solution of it by a demonstration that satisfies us indeed as to the fact (which no one doubts), but leaves the mental puzzle as before; and also Bergson’s Method of accounting for division by a comparison of the inner and the outer flux, wherein he seems to overlook the difficulty that for the purpose of comparison two points must be fixed, one in each flux, that is to say, the division in the flux must be regarded as already existing. In the physical sciences we are compelled to assume on the one hand the atomic or granular constitution of matter, in other words, manifoldness. On the other hand, if “action at a distance” is to be escaped, we are bound to assume a continuum of some sort like the ether. Again, in the organic world there is the manifold of structures and functions, and the unity of organism. To whatever object of inquiry we give our attention, we find ourselves not only restricted fundamentally to the two functions described, but we discover that to their insunderable co-operation we owe whatever of truth we possess.