Every formed disposition of the soul realizes its full nature in relation to and dealing with that class of objects by which it is its nature to be corrupted or improved.
Nature does nothing without a purpose. In children may be observed the traces and seeds of what will one day be settled psychological habits, though psychologically a child hardly differs for the time being from an animal.
Two characteristic marks have above all others been recognized as distinguishing that which has soul in it from that which has not - movement and sensation.
So, if we must give a general formula applicable to all kinds of soul, we must describe it as the first actuality [entelechy] of anatural organized body.