Concerning tropes, Peter van Inwagen says, "I don't understand what people can be talking about when they talk about those alleged items." (Existence: Essays in Ontology, Cambridge UP, 2014, p. 211.) He continues on the same page:
Consider two tennis balls that are perfect duplicates of each other. Among their other features, each is 6.7 centimeters in diameter, and the color of each is a certain rather distressing greenish yellow called "optical yellow." Apparently, some people understand what it means to say that each of the balls has its own color -- albeit the color of one is a perfect duplicate of the color of the other. I wonder whether anyone would understand me if I said that each ball had its own diameter -- albeit the diameter of one was a perfect duplicate of the diameter of the other. I doubt it. But one statement makes about as much sense to me as the other -- for just as the diameter of one of the balls is the diameter of the other (6.7 centimeters), the color of one of the balls is the color of the other (optical yellow).
Although van Inwagen couches the argument in terms of what does and does not make sense to him, the argument is of little interest if he is offering a merely autobiographical comment about the limits of his ability to understand. And it does seem that he intends more when he says that he doubts whether anyone would understand the claim that each ball has its own diameter. So I'll take the argument to be an argument for the objective meaninglessness of trope talk, not just the PvI-meaninglessness of such talk:
1. It is meaningful to state that each ball has its own color if and only if it is meaningful to state that each ball has its own diameter.
2. It is not meaningful to state that each ball has its own diameter.
3. It is not meaningful to state that each ball has its own color.
4. Talk of tropes is meaningless.
The argument is valid, and (1) is true. But I don't see why we should accept (2). So I say the argument is unsound.
It is given that the two tennis balls have the same diameter. But all that means is that the diameter of ball A and the diameter of ball B have the same measurement, 6.7 cm. This fact is consistent with there being two numerically distinct particular diameters, the diameter of A and the diameter of B.
What's more, the diameters have to be numerically distinct. If I didn't know that the two balls were of the same diameter, I could measure them to find out. Now what would I be measuring? Not each ball, but each ball's diameter. And indeed each ball's own diameter, not some common diameter. I would measure the diameter of A, and then the diameter of B. If each turns out to be 6.7 cm in length, then we could say that they have the 'same diameter' where this phrase means that A's diameter has the same length as B's diameter. But again, this is consistent with the diameters' being numerically distinct.
There are two diameters of the same length just as there are two colored expanses of the same color: two yellownesses of the same shade of yellow. So I suggest we run van Inwagen's argument in reverse. Just as it is meaningful to maintain that the yellowness of A is numerically distinct from the yellowness of B, it is meaningful to maintain that the diameter of A is numerically distinct from the diameter of B. Looking at the two balls we see two yellownesses, one here, the other there. Similarly, measuring the balls' diameter, we measure two diameters, one here, the other there.
Again, this does not show that trope theory is true, but only that it makes sense. It makes as much sense as van Inwagen's proposal according to which optical yellow is an abstract property exemplified by the two balls.