That he marvellously defined change we may learn from this: for what is actually that which it is said to be, while it is in that state, would not be said to be changing in that respect; thus a man, so long as he is a man, would not change in regard to manhood, nor, if he is actually white, does he change with regard to whiteness so long as he is white. But if a man who is actually white were to be potentially black, since he was capable of becoming black, when the turning from whiteness to blackness occurred in him, as was natural, i.e., in accordance with this capacity to become black, he would then be said to turn black. And again, when the blackness as come about it then remains constant in him and he is no longer changing with regard to blackness, but is actually black. Thus nothing is changed qua actual; nor indeed qua potential: when it remains potential and merely suitable it would not be said to be changing. But when it sbeing transformed from being potential into actuality while retaining its potentiality, then it is said to be changing. So he reasonably added 'as such' in order that to emphasize the actualization of what remains potential. For when there ceases to be potentiality there is no longer change.
Simplicius, On Aristotle's Physics 3, J. O. Urmson, tr. Cornell UP (Ithaca, NY: 2002) p. 30. I happened to come across several of the works of Simplicius in this series for $2.40 each at Half Price Books; quite the deal. So I'm doing some reading of Simplicius.
