Aristotle's Definitions of the Soul: "De Anima" ii, 1-3

organs.6 This apparent inconsistency holds, moreover, not only between
the third definition and things Aristotle says elsewhere. It holds between
the third definition and the second. The second definition requires only
that to be ensouled7 a body must be in a certain state of readiness to engage
in one or another life function, whether it has organs or not. It will be said
that Aristotle wants to argue in the De A nima that only a body with organs
could be in such a state. But he doesn't argue for this. At best he merely
claims it (412 a 28, f.). And even this he does not do unambiguously. For he
allows that if a thing engages regularly by nature in patterned change of
place that is enough to make it alive (413 a 22-25). We know that he
believes that the stars and the spheres in which they move do this and that
he denies that they have organs. So we have good reason to want the second
definition of soul to cover the stars. If it covers the stars, however, then it
seems incompatible with the third definition.
It might be argued that the second and third definitions are not meant to
be equivalent on the ground that the "body with organs" mentioned in the
third definition is explicitly introduced in the text as a body of a more
restricted type than the "body which has life potentially" of the second
definition (412 a 27 - b 1). If this were so we could take the second
definition, which covers the stars, as the accurate one and regard the third
as covering not all of the living but only a certain part of it. But the third
definition is said to mention "something common to every soul" (412 b 4).
The fourth definition introduces further problems. It apparently says
that any natural body which has an internal source of patterned change is
ensouled. But in the Physics (192 b 9-23) Aristotle claims that all the
familiar natural bodies have an internal source of patterned change. (Cf.
De Caelo 268 b 27, ff.). So on his definition rocks would seem to be alive.
And Aristotle would deny that rocks are alive (De Anima 412 a 13-15).
Some will urge that this fourth claim is not a definition, that it only gives a
necessary condition for being an ensouled body and no more. But it must
do more to play the role Aristotle gives to it in its context (412 b 10-17). He
argues that the thing that keeps an axe from being alive is that it doesn't as
an axe have the kind of natural body that engages in its proper motion -
chopping - in the cgurse of nature from some internal impulse. But rocks
do engage in their proper motion under internal impulse in the course of
nature (Physics 192 b 12, ff. at b 18). So the argument would seem to
require that they are alive. Even if we treat the fourth claim as giving only a
necessary condition for being alive, moreover, that still creates problems.
For, again, the stars are alive and, hence, ensouled and they do not engage
in any proper natural movement under internal impulse (De Caelo 290 a
261