The Philosophy of Agamben by Mills: “Aristotle’s discussion of potentiality in Book Theta begins with rejecting the position of the Megarians, who argued that something only has potentiality when that potentiality or potency is functioning. For Aristotle, this leads to the absurd conclusion that a man is only a builder in the act of building, and is therefore without the potential to build when he is not building. Similarly, if one is sitting, then one is without the potential for standing, which effectively means that standing is impossible. Against this account, Aristotle defines potency or potentiality as a principle of change by which a thing is acted upon or acts upon itself. Further, in an ostensibly truistic formulation, he argues that a thing is or has potential to the extent that the thing of which it is potential is not impossible” (30).
“… Aristotle’s claim that potentiality or capacity must also necessarily imply the privation of potentiality or capacity. That is, ‘Incapacity and the incapable is the privation contrary to ‘capacity’…every capacity has a contrary incapacity for producing the same result in respect of the same subject’. […] For Agamben, the importance of this is that in its essence, potentiality is entwined with its opposite of impotentiality or incapacity; that is, potentiality ‘maintains itself in relation to its own privation'” (Mills 30).
And Agamben himself says, “to be potential means: to be one’s own lack, to be in relation to one’s own incapacity. Beings that exist in the mode of potentiality are capable of their own impotentiality; and only in this way do they become potential…” (Potentialities 182, italics in original).
Realism 