One thing remains to be said regarding the distinction between accidental and substantial compounds. We have defined the first to be a compound “of substance and accident,” or a compound “of essence and something accidentally superadded to it.” The second we defined to be a compound “of substances uniting in one essence or nature.” But, as we noticed, the authors pledged to the theory of substantial generations admitted of no “substantial” compound but that which was believed to consist of matter and substantial form; and accordingly all compounds the form of which was an accidental entity, say _composition_, were considered by them as accidental. We observe that composition, though an accidental entity, is nevertheless the “essential” form of the compound, and gives it its “first” actuality. If, then, the compound is a distinct essence, and has a distinct name, and is called a distinct “substance,” as water, iron, gold, etc., its form, though an accident, is an essential constituent of the specific substance. We cannot at present discuss the question of substantial generations; we only remark that, to avoid all useless disputes about words, a physical compound, when it contains nothing but what is needed for the constitution of its specific nature, may be called _Unum per se naturale_—_i.e._, a being essentially one; and when it has something accidentally superadded, it may be called _Unum per accidens_—_i.e._, a being accidentally one. This distinction of names, which is familiar to all philosophers, expresses the distinction of the things without having recourse to the terms of “substantial compound” and “accidental compound,” taken in the Peripatetic sense of the words. Thus, whilst the Peripatetics based their distinction between these compounds on a presumed difference between their forms, we draw our own from the presence or absence of anything not belonging to the specific nature of the compound. This we do in accordance with the true spirit of scholastic philosophy, not to say compelled by a philosophical necessity; for we know that the constituent form of a purely material compound, though essential with respect to the compound itself, is only an accident received in the substance of the components, as we may hereafter have an occasion to show. And now let us come to the attributes of complete beings. Principles of attributes and properties.