When sustentation is considered in connection with the formal complement of a being, it means _overlying_ in such a manner as to superinduce a new complement and a new subsistence. Such is the manner in which the Person of the Word sustains Christ’s humanity. This kind of sustentation implies hypostatic union and super‐completion. We might, therefore, divide sustentation into _conservative_, _substantive_, and _hypostatic_. The first is usually called _conservation_; the second might keep the name of _sustentation_; whilst the third might perhaps be fitly styled _personalization_, as this word seems adequately to express the nature of personal sustentation. As to the phrases, “to be in itself” and “to be by itself,” we have seen that their distinction is most important. It may be useful to add that, even in God, to be in himself and to be by himself are to be distinguished by a distinction of reason indeed, but which is grounded on a real foundation. God is essentially _a se_, _in se_, and _per se_—that is, of himself, in himself, and by himself. These three attributes are absolute, and belong to the divine nature as an absolute reality; but as in this absolute reality there are intrinsic relations of personalities, we may reflect that, in this relative order, _to be of himself_ can be considered as owing especially to God the Father, who does not proceed from any other person, but is himself the first principle of their procession; _to be in himself_ can be considered as having a special reference to God the Son, in whom the whole entity of the Father is found as in the substantial term of his eternal generation; and, lastly, _to be by himself_ can be explained by reference to the Holy Ghost, who is the essential complement of the Blessed Trinity, as that is said to be by itself which is ultimately complete in its own entity.