Genera and species are real, and so far, if we call them ideas, ideas or universals are real, as Plato and the old realists asserted. But when we understand by ideas or universals the simple abstractions or generalizations of the essential qualities or attributes of things, as whiteness, redness, roundness, hardness, beauty, justice, goodness, they are real only in their concretes or subject. Objects may be really white, red, hard, heavy; things may be really beautiful; actions may be really just, wise, and good; but what we call beauty, justice, wisdom, goodness, can exist only as attributes or qualities of being, and are real only in their concretes. They can be reflected by creatures, but have no reality as abstractions. Abstractions, as St. Thomas says, have a foundation in reality, because they are formed by the mind by way of abstraction from objects presented by experience, and experience can present only that which is real; but as abstractions they are nullities, as Rosceline rightly held. It is necessary, then, to distinguish between genera and species and abstractions, and it would save much confusion to drop the name of ideas as applied to them, and even as applied to the intermediary world supposed to be inserted between the object and subject, as that world is commonly represented. This intermediary world, we think, has been successfully assailed by the Scottish school as ordinarily understood; but we do not think that the scholastics meant by it what is commonly supposed. These intermediary ideas, or intelligible species, seem to me in St. Thomas to perform in intellectual apprehension the office performed by light in external vision, and to be very defensible. They are not the understanding itself, but they are, if we may be allowed the expression, the light of the understanding. St. Thomas holds that we know by similitude. But God, he says, is the similitude of all things, _Deus est similitudo omnium rerum_. Now say, with him and all great theologians, that God, who is light itself, is the light of the understanding, the light of reason, the true light that lighteth every man coming into this world, and the whole difficulty is solved, and the scholastics and the philosophy so long taught in our Catholic schools and seminaries are freed at once from the censures so freely bestowed on them by the Scottish school and others. We suspect that we shall find seldom any reason to dissent from the scholastic philosophy as represented by St. Thomas, when once we really understand it, and adjust it to our own habits of thought and expression.