PROPERTIES OF THE SON AND THE HOLY GHOST
Two properties must pertain to the Son: one whereby He is distinguished from the Father, and this is filiation; another whereby, along with the Father, He is distinguished from the Holy Ghost; and this is their common spiration. But no property is to be assigned whereby the Son is distinguished from the Holy Ghost alone, because as we said above, the Son and the Father are a single principle of the Holy Ghost. Similarly, no single property is to be assigned whereby the Holy Ghost and the Son together are distinguished from the Father. For the Father is distinguished from them by one property, namely, innascibility, inasmuch as He does not proceed. However, since the Son and the Holy Ghost proceed, not by one procession, but by several, they are distinguished from the Father by two properties. The Holy Ghost has only one property by which He is distinguished from the Father and the Son, and this is called procession. That there cannot be any property by which the Holy Ghost may be distinguished from the Son alone or from the Father alone, is evident from this whole discussion.
Accordingly five properties in all are attributed to the divine persons: innascibility, paternity, filiation, spiration, and procession.