From a U. K. reader:
I'm currently reading up on my substance dualism for a philosophy of mind course, and thought I'd pose a question to you. I heartily agree with your frequent calls to eschew the parody of dualism as positing a kind of soul-stuff, but given this, I wonder how you think of the ontological status of mental properties. Most physicalists claim that such properties inhere in a physical substance, but if we avoid talk of substance in preference of a subject (as you have, in my opinion rightly, done in the past) how are these mental properties a) grounded (to avoid a Humean bundle view) and b) ontologically possible. I remember you suggesting that say, the property of being odd was not based on a material substance, as it was associated with a non-material number. But presumably both properties and subjects (however these are related) are concreta. And I find it hard to see how that method works for them.
1. The reader asks about the ontological status of mental properties and how they are related to the items that instantiate them. First some examples. If I say 'I am feeling anxious,' I self-ascribe the non-intentional mental property of feeling anxious. If I say, 'I see a coyote,' I self-ascribe the intentional mental property of seeing a coyote. If I say, 'I weigh 180 lbs.,' I self-ascribe the physical property of weighing 180 lbs. Properties in general can be defined in terms of instantiation: properties are instantiable entities. Thus:
P is a property =df P is possibly such that it is instantiated.
Not all entities are instantiable: neither Socrates nor his singleton are instantiable. I assume that properties are universals where universals are repeatable entities and particulars are not. That properties are universals is of course controversial and will be denied by trope theorists. To maintain that properties are universals is to reject that form of nominalism according to which everything that exists is a particular. I also reject the form of nominalism according to which properties are linguistic in nature. What's more, I reject the conceptualist theory that properties are mental in nature. Thus I tend to think that both physical and mental properties are universals that can exist uninstantiated, and whose existence is independent of the existence of any (finite) mind. Mental properties are not 'in the mind' if what this means is that mental properties exist only as accusatives of mental acts. Nor do mental properties require for their existence the existence of any (finite) minds.
I should also say something about 'abstract' and 'concrete' inasmuch as my reader speaks of concreta. ('Concreta' is the plural of 'concretum' the latter referring to any concrete item.) I suggest the following definition:
X is concrete (abstract) =df X is (is not) causally active/passive.
Thus all and only the relata of causal relations are concrete, and everything else is abstract. This begs raises the question as to the ontological category of the causal relata (events? states? facts? substances?) but is too tangled a beard to untangle now. If it is assumed that (primary) substances can be causes, then both God and Socrates come out concrete by the above definition. What then would be abstract? Such items as Fregean (as opposed to Russellian) propositions, mathematical (as opposed to commonsense) sets, numbers, and other more exotic entities.
To be a concrete thing is not the same as to be a material thing! My coffee cup is concrete and material, but my seeing that it is empty is also concrete though immaterial. The seeing is concrete because it has a causal role to play. The desire to drink coffee, together with my perception of the cup's emptiness will cause me to get out of my chair to refill the cup.
Are properties abstract or concrete? I said that properties are universals (repeatables) whose existence does not depend on being instantiated or on the existence of (finite) minds. Properties are concrete only if they are causally active/passive. It would seem that they are neither. A spherical object can be smashed, but sphericity cannot be smashed, nor can it do any smashing. My being anxious can cause my heart rate to increase, but the property of being anxious can do no such thing. Some properties induce causal powers/liabilities in the things that instantiate them, but no properties have causal powers/liabilities. The property of being sharp induces in a knife the causal power to slice through flesh and tendons, but the property itself has no such power.
So I think it is reasonable to think of properties as abstract or causally inert entities. This leads to the question of the modal status of properties. If they don't depend for their existence on being instantiated, and they don't depend for their existence on being the accusatives of acts of finite minds, then it seems we ought to say that properties are necessary beings, where a necessary being is one that exists in all metaphysically possible worlds.
So much for a rough sketch of a possible ontological framework. The domain of entities divides into the mutually exclusive and jointly exhaustive subdomains of abstracta and concreta. The concreta subdivide into the mutually exclusive and jointly exhaustive subsubdomains of mental particulars and physical particulars.
2. There is clearly a distinction between mental and physical properties, and it is not merely a prima facie distinction: at ontological bottom there is this distinction. Thus one cannot identify the mental property of feeling anxious with any physical property. Mental properties are irreducible to physical properties. I won't argue for this as I am quite sure my correspondent agrees with it.
3. Physical properties are properties of physical particulars. Clearly, it is my body, a physical particular, that instantiates the physical property of weighing 180 lbs. When we say that this property is physical, we do not mean that the property itself is physical; what we mean is that the property is the sort of property that is instantiable by physical particulars. The same goes for mental properties. When we say that a property is mental, we do not mean that the property itself is mental; what we mean is that the property is the sort of property that is instantiable by mental particulars. Both mental and physical properties are abstract, whence it follows that physical properties are not themselves physical, nor are mental properties themselves mental.
4. The reader points out that most physicalists think of mental properties as properties of physical particulars. This is indeed how most physicalists think, but I find this physicalist view to be incoherent. Right now I am looking at a mountain. The mental property of looking at a mountain is not looking at a mountain, nor is this property in any way sentient or conscious or conscious of something. I am looking at a mountain. The mental event of my looking at a mountain is the instantiation by me, as subject of experience, of the mental property of looking at a mountain. The mental event is not the instantiation of the mental property by any such physical thing as my brain. It is not the case that any physical thing is looking at a mountain: my glasses are not looking at a mountain, nor my eyes, nor any part of my eyes, nor the neural pathways connecting eyes to visual cortex, nor the visual cortex, nor any part of the brain nor the whole brain, nor the whole body, nor the whole body-cum- environment of the body. I am looking at a mountain. No physical thing or collectionof physical things can be identified as the subject of experience. And of course no abstract thing can be identified as the subject of experience. The subject of experience is sui generis.
Property dualism is an advance over the reductive view according to which mental properties are reducible to physical properties. But how combine a dualism of properties with a monism of property-possessors, when these property possessors are all of them material? A mental event such as the seeing of a mountain has two constituents at least: a subject of the mental event and a property. Now it is simply impossible to understand how the subject of a mental event can be any physical thing. That is the crux of the matter. He who appreciates that, appreciates that property dualism is as hopeless as reductionism.
5. So what is wrong with the following view. There are concrete but immaterial subjects of experience and they instantiate various mental properties. Thus I, as subject of experience, instantiate the mental property of being anxious, and this is the state or event of my being anxious. My body, which cannot possibly be a subject of experience (though it can of course be an object of experience), instantiates the physical property of weighing 180 lbs, and this is the state or event of my weighing 180 lbs.
The reader wants to know how I avoid a Humean bundle view of the self. The short answer is that I avoid it by thinking of the relation of the subject of experience and its properties as a relation of instantiation, which is asymmetrical. Bundling relations are symmetrical. The reader also asks how mental properties are ontologically possible. The short answer here is that, e.g., the property of being anxious is a mental property, and it cannot be reduced to any physical property. Now the mental property is actual, when it follows by the familiar modal principle ab esse ad posse that it is actual!
No doubt numerous objections could be brought against what I just written, but I am quite confident that any alternative view will suffer the same fate.