The Visitor from Elea now closes the discussion about what-is-not and turns his attention to what-is. He describes a contemporary debate in mythological terms, as being like a battle of gods and giants, reminiscent of some scenes in Hesiod’s Theogony.[22] One group, the giants, identifies body (sōma) with being and refuses to consider any non-physical entity as real. The opposing group, the gods, stoutly maintains that certain intelligible incorporeal forms (noēta atta kai asōmata eidē) are what is really real, and that the bodies championed by their opponents are no more than ephemeral processes, becomings rather than beings.[23]
Evidently the Visitor is rehearsing a debate between those we now call materialists and those we call idealists, theorists who say that reality consists exclusively of physical objects and their properties, on the one hand, and those who say that reality consists exclusively of non-physical entities such as forms or souls or the like, on the other. Clearly Plato has cast his lot with the idealists and has diligently defended their position against the materialists. What is remarkable about Plato’s present discussion is that the Visitor is not going to endorse either party in the debate. He is looking for a middle ground which both parties can agree on, and which can provide a starting point for some sort of compromise going forward.
The Visitor asks Theaetetus to engage an open-minded materialist and ask him whether he does not believe in living things. Yes. And do not living things have souls? Yes. Then you must believe in souls. And are not intelligence, justice, and injustice located in souls? Yes. And are souls, and intelligence, and justice, and the like visible or invisible? Then reality cannot consist solely of sensible objects, but must include the non-sensible and intelligible entities.
How then shall we characterize what is real? “I suggest,” says the Visitor, “that anything that possesses any kind of natural ability either to affect another thing or to be affected in even the smallest way by the most insignificant thing, even if this happens only one time, this is really real. I propose, then, to define reality as nothing other than power (dunamis).”[24]
Now we must turn, the Visitor continues, to the other group, “the friends of the Forms.” This party makes a strong distinction between changeable phenomena of sensation and the timeless being of Forms, which are changeless and perfect. These friends of the Forms would not be comfortable with the previous definition of being as power, because the power to affect and be affected involves change. But think about it: do life and intelligence exist without any change or adaptation? “Can what has intelligence and life and soul remain completely motionless even though it is inanimate?” In no way. “Then both what is moved and motion itself must be accepted as real.”[25]
It turns out, then, that both what is constant and what changes are preconditions of intelligence and knowledge. We have found a middle ground between the materialists and the idealists: there are animate objects, on the one hand, and powers to affect and be affected. But intelligence consists not only of awareness of changeless ideals, but also of the ability to adapt to changing situations. Reality, then, must consist of both change and constancy, of both bodies and souls. The battle of gods and giants concludes with a truce, and the promise of a peace treaty.[26]
[22] Compare the war of the Olympian gods with the Titans, Hesiod Theogony 617-735.
[23] Plato Sophist 246a-c.
[24] Plato Sophist 247d-e.
[25] Plato Sophist 249a-b.
[26] Plato Sophist 246a-249d.