The source of this groundless charge lies partly in the mistaken conception of accident and substance as concrete entities superadded the one to the other; partly in the mistaken notion that the union of substance and accidents cannot result in a real unity, that there cannot be more or less perfect grades of real unity (27); and partly in the false assumption that real distinction always implies mutual separability of concrete entities. Of these errors we need only refer to that concerning unity. Modern philosophers not uncommonly conceive the union of substance and accidents as being necessarily a mere _mechanical_ union or aggregation, and oppose it to “organic” unity which they regard as a real unity involving the richness of an energetic, “living” multiplicity. This involves a misrepresentation of the traditional scholastic view. The union of substance and accident is not a mechanical union. Nothing could be farther from the minds of the scholastic interpreters of Aristotle than the conception of the ultimate principles of the universe of our experience as inert entities moved according to purely mechanical laws; or of the individual concrete being as a mere machine, or a mere aggregate of mechanical elements. They recognized even in the individual inorganic substance an internal, unifying, active and directive principle of all the energies and activities of the thing—its substantial form. And if this is all those philosophers mean by the metaphorical transference of the terms “organic unity,” “internal living principle of development,” etc., to the mineral world, they are so far in accord with the traditional scholastic philosophy;(274) while if they mean that all substances are principles of “vital” energy, or that all reality is one organic unity, in the literal sense of these terms, they are committing themselves either to the palpably false theory of pan-psychism, or to the gratuitous reassertion of a very old and very crude form of monism. By “organic” unity we understand the unity of any living organism, a unity which is much more perfect than that of the parts of a machine, or than any natural juxtaposition of material parts in an inorganic whole; for the organs, though distinct in number and in nature from one another, are united by an internal principle to form one living individual, so that if any organ were separated from the living organism it would cease to be an organ.(275) But organic unity is not by any means the most perfect kind of unity conceivable.(276) The living organism exists and develops and attains to the perfection of its being only through a multiplicity of integral parts extended in space. The spiritual substance is subject to no such dispersion of its being. From its union with the faculties whereby it attains to its natural development, there results a real unity of a higher order than that of any organism.