Sketch of a basis for arguments against metaphysical realism

 I'll start with this old chestnut: possible worlds, state-descriptions, individual objects as instantiations of the properties that are their so-called object essences, etc. all seem to be a way of describing the distribution of properties across objects such that these distribution of properties across objects serve as the truthmakers for modal claims. Actually, with Jubien's properties in Platonic heaven and the instantiation relation things are a bit different -- it's the entailment relation between different sorts of properties (that exist above the Great Line of Being) that determine de dicto modal claims. So, for instance, if property A bears the entailment relation to property B, then any object which instantiates A must (with modal force) also instantiate B, and the modal claim, 'Necessarily, if x is A then x is B' is true.
 I'll say more about the possible worlds / state-descriptions / truthmakers as distributions of properties across a set of objects first, then say something about Jubien's approach. A most basic criticism of this approach (along with a metaphysical realist view) can be put with the following question. How do carve the world into 'individual objects' before settling on the distribution of properties across those objects? If I want an examination of possible worlds to tell me whether 'my truck could have been red' is true, I must have a way to pick out and think about my truck among all the other stuff. Could my truck have been something else? Could it have been my television? It's hard to know how to answer these questions if we don't have some conceptual knowledge about how to pick out trucks from among the other parts of the physical environment. I've argued that conceptual knowledge includes modal knowledge. One wouldn't have the concept TRUCK unless he could pick out (and think about) trucks in counterfactual scenarios. So, at least at first glance it seems that some modal knowledge is required even to think coherently about possible worlds or state-descriptions. If we must have modal knowledge to make sense of these things why not look to the source of that modal knowledge as the beginning of an explanation of the truth of falsity of statements like 'my truck could have been red'. That's the sketch, anyway.
 Now, as far as Jubien's stuff goes, I think he may leave a gap into which skepticism about modal knowledge could intrude. Let me say more. Of course, for Jubien, modality is analyzed mostly by the entailment relation which may or may not hold between occupants about the GLB. First, it's hard to see how we any epistemic contact with occupants above the GLB (that is Platonic properties) being that we cognizers are located below the line, unless we have some faculty beyond space and time which allows us epistemic contact with abstracta (this faculty might be reasoning, intellectual insight or some such). If we did have some such faculty, then it's easy to see how we could simply "observe" whether the relation relation held between such properties, and in so doing easily determine whether the modal claims that expressed these particular relationships were true or false. I think there are two immediate problems the first of which has an easy solution for Jubien. First, if we have such a faculty, when isn't the truth of falsity of an arbitrary modal claim transparent to us -- as it's immediate whether a certain stick is longer than another or not. Answer - we "see" above the GLB by reasoning and that's more difficult than simply seeing. A related point is that some modal truth are easier to affirm than others. For instance, it's obviously true that 'Necessarily, if x is red, then x is colored'. On the platonic ability approach, the entailment relation between the property of being red and the property of being colored is as obvious as being able to see the difference between a stick of length one meter and a stick of length two meters. The second difficulty seems more troubling. It can be put most brutely by the following questions. What is the relationship for Platonic properties and our words for them? Supposing there is the platonic property of being red, what is it's relationship with the predicate 'is red'? There are two options -- either there are is no obvious relationship between properties and our predicates or they are related in some way. If there's no obvious relationship then the semantics of modal claims (and our knowledge of the truths of falsity of sentences which express these claims), and the relationship of properties that are the truthmakers for these claims, then we're headed to skepticism of modal knowledge for the truthmakers are properly related to that for which they're truthmakers. If there is some relation, then it seems that we're back to the sort "two-tiered structure" of modality that we saw in the previous paragraph. It seems that being a competent speaker involves a modal ability. For instance, a speaker who's competent with the term 'truck' should be able to correctly identify a truck if he were presented with one. (emphasis to show the modal dimension of the ability). If being a competent speaker involves a modal ability, and modality was meant to be analyzed in terms of the entailment relation, then being a competent speaker involves having some knowledge about the entailment relation that holds between occupants of the above of the GLB. A few things: (1) I'm not sure if this is a riff against a reductive account of modality, (2) if we could tell a story about concept possession that explained our ability as competent speakers, then it seems that we could explain (give a semantics for) modal claims (sentences) without making use of the platonic machinery. Well ... spend some more time on this...