11. (16). What sensible man, after having thus considered the nature
of the soul, could still doubt of the immortality of a principle which
derives life from naught but itself, and which cannot lose it? How
could the soul lose life, since she did not borrow it from elsewhere,
and since she does not possess it as fire possesses heat? For, without
being an accident of fire, the heat, nevertheless, is an accident
of its matter; for fire can perish. But, in the soul, life is not an
accident that comes to add itself to a material subject to constitute a
soul. In fact, there is here an alternative: either life is a genuine
"being," which is alive by itself; in which case this "being" is
the soul that we are seeking to discover, and immortality cannot be
refused her; or the soul is a composite, and she must be decomposed
until we arrive at something immortal which moves by itself; and such
a principle could not be subject to death. Further, when (Stoics)
say that life is only an accidental modification of matter, they are
thereby forced to acknowledge that the principle that imparted this
modification to matter is immortal, and incapable of admitting anything
contrary to what it communicates (that is, life, as said Plato, in his
Phaedo[87]), but there is only a single nature that possesses life in
actualization.