In my post, The Presentation Argument for Property Dualism, I examined an argument that targets property reduction and attempts to conclude that for any purported reduction of one property to another, there is a residual appearance left over. The residual appearance requires some property to which it corresponds, so any attempt at property reduction actually generates more properties.
One objection is that this argument relies on property intensionalism. What this means is that we individuate properties by how we think of them rather than by extension. The argument for property dualism seems to require this principle of individuation:
(PI) If it’s not a priori that <F> and <G> are coextensive, then F and G are not identical.
The principle says that if it isn’t a priori knowable that the concepts <F> and <G> have the same extensions, then the properties F and G are not identical. PI is at home with the view that the epistemology of properties is wholly a priori. In essence, if we have two concepts that on reflection seem not to have (necessarily) identical extensions, then they pick out distinct properties. We can know which properties exist by analyzing our concepts of them.
The problem with PI is that it just seems like a form of property intensionalism. After all, why think that our a priori reflection on the extensions of our concepts reliably yields facts about properties that exist independently of those concepts? It seems like a massive coincidence without some dependence between properties and our concepts of them. But any dependence between concepts and properties that allows one to derive PI runs the risk of making properties unacceptably mind-dependent. By unacceptably mind-dependent, I mean there must be some metaphysical dependency between properties and concepts such that it is more than just a coincidence that a priori reflection on concepts produces knowledge about properties in a reliable manner. Such metaphysical dependency is either a God-given pre-established harmony between concept and property, or some kind of idealism about properties, which ultimately amounts to idealism about almost everything.
The proponent of the presentation argument could respond by saying that PI and property intensional are conceptually distinct. One could maintain PI without embracing the anti-realist sounding doctrine of property intensionalism, as is possible in my example of pre-established harmony. Perhaps proponents of the presentation argument could just say that our concepts reliably pick out properties that are not themselves individuated by those concepts.
For the view that concepts reliably pick out properties that aren’t individuated by those very concepts to work in the presentation argument, the appearance properties must not be individuated epistemically, but rather metaphysically. However, appearance properties seem to be individuated epistemically. After all, appearances are the wheelhouse of the internalist epistemologist, and as such they seem to be subject to intensional individuation if anything is. So, even if we grant that PI is compatible with an extensionalist individuation scheme for properties, the presentation argument still seems to rely on things whose very nature entails intensional individuation conditions.
Given that the presentation argument’s reliance on PI is part and parcel with intensional individuation conditions for (at least) appearance properties, there is another problem proponents of the argument must face. An extensionalist about property individuation holds to objective individuation conditions for properties. For example, the dispositional properties revealed by modern physics are individuated objectively; they are not individuated by something like PI. The property intensionalist is going to accept the same properties as the extensionalist, since the extensionalist typically endorses a scientific methodology for discovering properties. That scientific methodology will yield results that both the intensionalist and extensionalist have independent reasons to accept. But the extensionalist has an advantage here, since all the properties both she and the intensionalist can agree to are those properties that we consider causally efficacious. All the causal work in the world can be done in virtue of the properties that a pure extensionalist individuation scheme is committed to. The intensionalist is going to have additional properties, and those properties are either causally inert or causally efficacious. If they are causally efficacious then they causally overdetermine the events they enter into alongside the extensionally individuated properties. If they are causally inert, then they are committed to epiphenomenal properties.
The first horn of the dilemma assumes that causal overdetermination is theoretically vicious, but there are reasons to doubt this. If the intensionalist has independent reasons to think that causal overdetermination is ok, or a good thing to believe in, embracing the first horn shouldn’t bother her. The second horn is more problematic, though. We have good reasons to think that mental states are able to enter into causal relations. The appearances cited in the presentation argument seem to cause proponents of the argument to advance it, and they cause me to reflect on it, as well as property individuation. If those appearances weren’t there, theorists would lack motivation to formulate the presentation argument. Even less plausibly, embracing the second horn would entail that appearances are not among the things that cause us to discuss appearances. I, for one, am not brave enough to accept such a result.
So, the proponent of the presentation argument must accept PI, and thereby is either committed to pre-established harmony between concepts and properties, a massive coincidence, or idealism (anti-realism) about properties. If the proponent attempts to disavow property intensionalism yet hold to PI, she will find herself lapsing back into property intensionalism once she introduces appearance properties into the mix. The proponent is also committed to the same properties as the extensionalist, as well as many more properties individuated intensionally. But, there are plausible reasons to think that the causal work in the world is done by the properties we individuate extensionally. So, the proponent of the argument must either embrace causal overdetermination, or epiphenomenalism about appearances. I argued that the latter is less plausible than the former, so the proponent must adopt overdetermination. At this point in the dialectic, the proponent must give us good, independent reasons to think overdetermination obtains in the causal order. Until then, we remain at liberty to deny the conclusion of the presentation argument, and remain physicalists.
 Howell 104-105.
 Ibid 105.
 Ibid 106
 Ibid 106-107
 Ibid 107-108.
 Ibid 108.
 Ibid 108-109.
 There’s a strong case to be made for science as the most reliable way for detecting many if not all properties that are instantiated, and that case can be made independently of the individuation debate.
 Cf. Sider 2003.
Howell, Robert J. Consciousness and the Limits of Objectivity: The Case for Subjective Physicalism. Oxford: Oxford UP, 2013. Print.
Sider, Theodore. “What’s So Bad About Overdetermination?” Philosophy and Phenomenological Research 67.3 (2003): 719-26. Web.