Further, Boethius says of God (De Trin. i), that "this is
truly one which has no number." But plurality implies number.
Therefore there are not several persons in God.

Obj. 4: Further, where number is, there is whole and part. Thus,
if in God there exist a number of persons, there must be whole and
part in God; which is inconsistent with the divine simplicity.

_On the contrary,_ Athanasius says: "One is the person of the Father,
another of the Son, another of the Holy Ghost." Therefore the Father,
and the Son, and the Holy Ghost are several persons.

_I answer that,_ It follows from what precedes that there are several
persons in God. For it was shown above (Q. 29, A. 4) that this
word "person" signifies in God a relation as subsisting in the divine
nature. It was also established (Q. 28, A. 1) that there are
several real relations in God; and hence it follows that there are
also several realities subsistent in the divine nature; which means
that there are several persons in God.

Reply Obj. 1: The definition of "person" includes "substance," not as
meaning the essence, but the _suppositum_ which is made clear by the
addition of the term "individual." To signify the substance thus
understood, the Greeks use the name "hypostasis." So, as we say,
"Three persons," they say "Three hypostases." We are not, however,
accustomed to say Three substances, lest we be understood to mean
three essences or natures, by reason of the equivocal signification
of the term.

Reply Obj. 2: The absolute properties in God, such as goodness and
wisdom, are not mutually opposed; and hence, neither are they really
distinguished from each other. Therefore, although they subsist,
nevertheless they are not several subsistent realities--that is,
several persons. But the absolute properties in creatures do not
subsist, although they are really distinguished from each other, as
whiteness and sweetness; on the other hand, the relative properties
in God subsist, and are really distinguished from each other (Q. 28,
A. 3). Hence the plurality of persons in God.

Reply Obj. 3: The supreme unity and simplicity of God exclude every
kind of plurality of absolute things, but not plurality of relations.
Because relations are predicated relatively, and thus the relations
do not import composition in that of which they are predicated, as
Boethius teaches in the same book.

Reply Obj. 4: Number is twofold, simple or absolute, as two and three
and four;