Aristotle has just finished explaining how a difference in contradictories shows a difference in meaning. Now he continues his discussion of the second tool by talking about how privation and possession show a difference in meaning. He does this in Topics, Book 1.
Moreover, examine the case of terms that are opposed as privation and possession- for if the one term is used in more than one way, then so will the remaining term: e.g. if to perceive is used in more than one way, as applied to the soul and to the body, then to be imperceptive too will be used in more than one way, as applied to the soul and to the body. That the opposition between the terms now in question depends upon privation and possession is clear, since animals naturally possess each kind of perception, both as applied to the soul and as applied to the body.
We should also consider the difference in meaning that is shown by a difference in what the privation means. A privation is something that something lacks that it should have. For example, we can speak of perception as it relates to the mind and to the body. A privation of perception is to fail to perceive because something is lacking. As it relates to the body, a privation of perception is blindness. But as it relates to the mind, we cannot speak of the mind as being blind except metaphorically. Instead we speak of the person as being slow, or stupid. Therefore, perception means something different when applied to the senses than it means when applied to the mind. We should see that privation is an opposite of the term.
Next, Aristotle discusses how different forms of the word may indicate a difference in meaning.