Whether to Live Belongs to All Natural Things?
Objection 1: It seems that to live belongs to all natural things. For
the Philosopher says (Phys. viii, 1) that "Movement is like a kind of
life possessed by all things existing in nature." But all natural
things participate in movement. Therefore all natural things partake
of life.
Obj. 2: Further, plants are said to live, inasmuch as they have in
themselves a principle of movement of growth and decay. But local
movement is naturally more perfect than, and prior to, movement of
growth and decay, as the Philosopher shows (Phys. viii, 56, 57).
Since then, all natural bodies have in themselves some principle of
local movement, it seems that all natural bodies live.
Obj. 3: Further, amongst natural bodies the elements are the less
perfect. Yet life is attributed to them, for we speak of "living
waters." Much more, therefore, have other natural bodies life.
_On the contrary,_ Dionysius says (Div. Nom. vi, 1) that "The last
echo of life is heard in the plants," whereby it is inferred that
their life is life in its lowest degree. But inanimate bodies are
inferior to plants. Therefore they have not life.
_I answer that,_ We can gather to what things life belongs, and to what
it does not, from such things as manifestly possess life. Now life
manifestly belongs to animals, for it said in _De Vegetab._ i [*De
Plantis i, 1] that in animals life is manifest. We must, therefore,
distinguish living from lifeless things, by comparing them to that by
reason of which animals are said to live: and this it is in which life
is manifested first and remains last. We say then that an animal
begins to live when it begins to move of itself: and as long as such
movement appears in it, so long as it is considered to be alive. When
it no longer has any movement of itself, but is only moved by another
power, then its life is said to fail, and the animal to be dead.
Whereby it is clear that those things are properly called living that
move themselves by some kind of movement, whether it be movement
properly so called, as the act of an imperfect being, i.e. of a thing
in potentiality, is called movement; or movement in a more general
sense, as when said of the act of a perfect thing, as understanding
and feeling are called movement. Accordingly all things are said to be
alive that determine themselves to movement or operation of any kind:
whereas those things that cannot by their nature do so, cannot be
called living, unless by a similitude.
Reply Obj. 1: These words of the Philosopher may be understood either
of the first movement, namely, that of the celestial bodies, or of
the movement in its general sense. In either way is movement called
the life, as it were, of natural bodies, speaking by a similitude,
and not attributing it to them as their property. The movement of the
heavens is in the universe of corporeal natures as the movement of
the heart, whereby life is preserved, is in animals. Similarly also
every natural movement in respect to natural things has a certain
similitude to the operations of life. Hence, if the whole corporeal
universe were one animal, so that its movement came from an
"intrinsic moving force," as some in fact have held, in that case
movement would really be the life of all natural bodies.
Reply Obj. 2: To bodies, whether heavy or light, movement does not
belong, except in so far as they are displaced from their natural
conditions, and are out of their proper place; for when they are in
the place that is proper and natural to them, then they are at rest.
Plants and other living things move with vital movement, in
accordance with the disposition of their nature, but not by
approaching thereto, or by receding from it, for in so far as they
recede from such movement, so far do they recede from their natural
disposition. Heavy and light bodies are moved by an extrinsic force,
either generating them and giving them form, or removing obstacles
from their way. They do not therefore move themselves, as do living
bodies.
Reply Obj. 3: Waters are called living that have a continuous
current: for standing waters, that are not connected with a
continually flowing source, are called dead, as in cisterns and
ponds. This is merely a similitude, inasmuch as the movement they are
seen to possess makes them look as if they were alive. Yet this is
not life in them in its real sense, since this movement of theirs is
not from themselves but from the cause that generates them. The same
is the case with the movement of other heavy and light bodies.
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