n nature. Secondly, because
in all beings whose entire matter is contained in one individual
there is only one individual in the species: as is clearly the case
with the sun, moon and such like. Thus there would only be one
individual of the human species. Thirdly, because multiplication of
matter cannot be understood otherwise than either in respect of
quantity only, as in things which are rarefied, so that their matter
increases in dimensions; or in respect of the substance itself of the
matter. But as long as the substance alone of matter remains, it
cannot be said to be multiplied; for multitude cannot consist in the
addition of a thing to itself, since of necessity it can only result
from division. Therefore some other substance must be added to
matter, either by creation, or by something else being changed into
it. Consequently no matter can be multiplied save either by
rarefaction as when air is made from water; or by the change of some
other things, as fire is multiplied by the addition of wood; or
lastly by creation. Now it is manifest that the multiplication of
matter in the human body does not occur by rarefaction: for thus the
body of a man of perfect age would be more imperfect than the body of
a child. Nor does it occur by creation of fresh matter: for,
according to Gregory (Moral. xxxii): "All things were created
together as to the substance of matter, but not as to the specific
form." Consequently the multiplication of the human body can only be
the result of the food being changed into the true human nature.
Fourthly, because, since man does not differ from animals and plants
in regard to the vegetative soul, it would follow that the bodies of
animals and plants do not increase through a change of nourishment
into the body so nourished, but through some kind of multiplication.
Which multiplication cannot be natural: since the matter cannot
naturally extend beyond a certain fixed quantity; nor again does
anything increase naturally, save either by rarefaction or the change
of something else into it. Consequently the whole process of
generation and nourishment, which are called "natural forces," would
be miraculous. Which is altogether inadmissible.

Wherefore others have said that the human form can indeed begin to
exist in some other matter, if we consider the human nature in
general: but not if we consider it as in this individual. For in the
individual the form remains confined to a certain determina