I've been looking at T. Irwin's interpretation of Plato on the Compresence of Opposites. You will recall that this was recommended as a philosophically more sophisticated view than, for instance, the simple and perhaps simplistic idea that Plato believed that all things were infested with contraries because all things were changing.
The simple and simplistic idea is expressed in the following argument:
1. Each thing, in any respect in which it is perceptible, is changing.According to this argument, Flux implies Compresence, because change requires that the changing thing somehow partake simultaneously both of the terminus a quo and the terminus ad quem of the change. (Note: on this view, change in the true sense is not a mere succession of qualities, e.g. a thing changes if at time T1 it is F and at some later time T2 it is not-F.)
2. Anything which changes, in the respect in which it changes, has compresent opposite properties.
3. Thus, each thing, in any respect in which it is perceptible, has compresent opposite properties.
Now here's a curiosity about Irwin's interpretation. As we saw, he re-interprets Compresence in a very broad way, and as being about properties rather than particulars. For Irwin, Compresence becomes, in effect, the view that each property is such that there is at least one other property for which it is not a sufficient condition; i.e. for each property there is at least one other property that fails to be fixed when the former is fixed. Thus on this view circularity has opposites 'present in it', because to say that something is circular is to imply nothing about whether it is (say) green or not-green. So (Irwin would have it), both green and not-green are present in circularity.
Yet, at the same time, Irwin acknowledges that Plato is committed to a Doctrine of Flux. Below I give the relevant passages from Plato's Ethics below (from pages 161-2).
Now, when you read these passages, ask yourself: How can Irwin acknowledge all of these things, and yet still give such a weak reading of Compresence? If Flux implies Compresence of Opposites, in the sense of the simultaneous presence of contrary or contradictory properties in particulars, how can Irwin consistently affirm Flux but deny Compresence in that sense? Or is Irwin committed to two different accounts of Compresence, the sophisticated and the simple?
I'll give you my take on this in a later post.
...Plato himself speaks of change in sensibles and seems to regard this as a reason for denying that they can be objects of knowledge and definition. In the Cratylus he suggests that knowledge requires the existence of unchanging forms as objects of knowledge; even if sensibles are all in flux, forms must be exempt from flux (Cra. 439c6-440d2). In this passage Plato does not actually affirm that sensibles are in flux, but in other dialogues he seems to affirm precisely that; after he has argued that the Forms are different from sensibles, he claims that sensibles undergo constant change, whereas Forms are completely unchanging (Phd. 78c10-e4; R. 495a10-b3, 508d4-9, 518e8-9, 525b5-6, 534a2-3). ...
[Plato] explains who Protagoras' belief in the truth of appearances leads to the doctrine that 'nothing is any one thing itself by itself', because, for instance, you cannot call anything large without its appearing small,or heavy without its appearing light (Tht. 152d2-6). These appearances of compresence are the result of motion, change, and mingling, so that everything merely comes to be (hard, soft, light, heavy, and so on) and nothing stably is what we take it to be (152d2-e1).