Obj. 1: Although this or that singular may not be definable,
yet what belongs to the general idea of singularity can be defined;
and so the Philosopher (De Praedic., cap. De substantia) gives a
definition of first substance; and in this way Boethius defines
person.

Reply Obj. 2: In the opinion of some, the term "substance" in the
definition of person stands for first substance, which is the
hypostasis; nor is the term "individual" superfluously added,
forasmuch as by the name of hypostasis or first substance the idea of
universality and of part is excluded. For we do not say that man in
general is an hypostasis, nor that the hand is since it is only a
part. But where "individual" is added, the idea of assumptibility is
excluded from person; for the human nature in Christ is not a person,
since it is assumed by a greater--that is, by the Word of God. It is,
however, better to say that substance is here taken in a general
sense, as divided into first and second, and when "individual" is
added, it is restricted to first substance.

Reply Obj. 3: Substantial differences being unknown to us, or at
least unnamed by us, it is sometimes necessary to use accidental
differences in the place of substantial; as, for example, we may say
that fire is a simple, hot, and dry body: for proper accidents are
the effects of substantial forms, and make them known. Likewise,
terms expressive of intention can be used in defining realities if
used to signify things which are unnamed. And so the term
"individual" is placed in the definition of person to signify the
mode of subsistence which belongs to particular substances.

Reply Obj. 4: According to the Philosopher (Metaph. v, 5), the word
"nature" was first used to signify the generation of living things,
which is called nativity. And because this kind of generation comes
from an intrinsic principle, this term is extended to signify the
intrinsic principle of any kind of movement. In this sense he defines
"nature" (Phys. ii, 3). And since this kind of principle is either
formal or material, both matter and form are commonly called nature.
And as the essence of anything is completed by the form; so the
essence of anything, signified by the definition, is commonly called
nature. And here nature is taken in that sense. Hence Boethius says
(De Duab. Nat.) that, "nature is the specific difference giving its
form to each thing," for the specific difference completes the
definition, and is der