Our only object in setting down the various examples just given is to illustrate the general scholastic teaching on the doctrine of distinction. In themselves they are not beyond dispute, for the general doctrine of distinction is not easy of application in detail; but they will be sufficient for our present purpose. Probably the greatest difficulty in applying the general doctrine will be found to lie in discriminating between virtual distinctions—especially perfect virtual distinctions—and real distinctions.(119) And this difficulty will be appreciated still more when we learn that a real distinction does not necessarily involve _separability_ of the objects so distinguished. In other words there may be, in a composite existing individual being, constitutive factors or principles, or integral parts, each of which is a positive real entity, really distinct from the others, and yet incapable of existing separately or in isolation from the others. “Separability,” says Mercier,(120) “is one of the signs of a real distinction; but it is neither essential to, nor a necessary property of the latter. Two separable things are of course really distinct from each other; but two entities may be really distinct from each other without being separable or capable of existing apart from each other. Thus we believe that the intellect and the will in man are really distinct from each other, and both alike from the substance of the human soul; yet they cannot exist isolated from the soul.” Therefore, even though the objects which we apprehend as distinct, by means of distinct concepts, be understood to be such that they cannot actually exist in isolation from each other, but only as united in a composite individual being, still if it can be shown that each of them has its own proper reality independently of our thought, so that the distinction between them is not the result of our thought, or introduced by our thought into the individual thing or being which we are considering, then the distinction must be regarded as real. If, on the other hand, it can be shown that the different aspects which we apprehend in any _datum_ by means of distinct concepts have not, apart from the consideration of the mind, apart from the analytic activity of our own thought, each its own proper reality, but are only distinct mental views of what is objectively one and the same reality, then the distinction must be regarded as logical, not real,—and this even although there may be in the richness and fulness of that one reality comparatively to the limited capacity of our minds, as well as in the very constitution and modes of thought of our minds themselves, a reason or basis for, and an explanation of, the _multiplicity of concepts_ whereby we attain to an understanding of some _one reality_.