This post advances the discussion in the ComBox attached to Could Brains Have Mental Properties?
It would be very easy to be a property dualist in the philosophy of mind if one were also a substance dualist. What I am having trouble understanding is how a property dualist can be a substance monist. In contemporary discussions, the one category of substances is that of material substances. 'Property dualism,' then, is an abbreviated name for the position in the philosophy of mind according to which mental and physical properties are mutually irreducible -- hence the dualism -- but had by the only kind of substances there are, material substances. Hence the monism. But having employed the traditional jargon, I'll now drop the irridescent word 'substance' which will undoubtedly cause many to stumble and use 'particular' instead. A particular is an unrepeatable entity. It needn't be a continuant. Events and processes count as particulars.
To come directly to my difficulty. How can an irreducibly mental property be instantiated by a physical particular? An irreducibly mental property is one that is not identical with, or reducible to, any physical property. Examples of mental properties: being in pain; thinking about Thanksgiving dinner; having a blue sensation; wanting a cup of coffee. This post assumes that at least some mental properties are irreducibly mental. Various arguments have been given; this is not the place to rehearse them. An irreducibly physical property is one that is not identical with, or reducible to, any mental property. Examples of physical properties: impedance, ductility, motion, solubility, weighing 10 kg. I will assume that all physical properties are irreducibly physical. (It is not that I rule out idealism; it's that the goddess of blogging reminds me that brevity is the soul of blog.)
To further focus the question we need to exclude relational properties. Weaver's Needle has the property of being thought about by me now. So a physical particular has now an irreducibly mental property. But this is unproblematic because the property in question is relational: it does not affect the Needle in its intrinsic nature. But if my brain is what does the thinking in me, and I am thinking about Weaver's Needle, it is not so easy to understand how my brain, a physical thing, can have the irreducibly mental intrinsic property, thinking about Weaver's Needle. (If you think that is not an intrinsic property, substitute wanting a sloop, given that there is no particular sloop in existence that I want.)
So in what follows by 'irreducibly mental properties' I mean 'irreducibly mental intrinsic properties.'
My question is whether the following tetrad is consistent:
1. There are irreducibly mental properties.
2. There are irreducibly physical properties.
3. All particulars are physical particulars.
4. Some but not all particulars instantiate irreducibly mental and irreducibly physical properties.
You might think there is no problem. Color and shape properties are mutually irreducible. Yet some physical particulars instantiate both color and shape properties. A red ball is both red and spherical despite the mutual irreducibility of redness and sphericity. Imagine that the red ball is red all the way through and not red merely on its surface. This will preempt one from saying that the ball is red in virtue of a proper part of it being red.
So why can't mental and physical properties be had by one and the same physical particular? Doesn't the analogy show that the tetrad is consistent? Mental properties are to physical properties as color properties are to shape properties. Just as one and the same physical particular, a ball say, can be both red and spherical, one and the same particular, a brain (or a portion of a brain or an event or process in a brain) can be both located in a region of space and thinking about Boston or feeling nostalgic.
I will now argue that the analogy is hopeless.
A Point of Disanalogy
Colors and shapes are mutually irreducible, but they are also such that color properties cannot be instantiated without shape properties being instantiated, and vice versa. I am talking about colors and shapes in Sellars' "manifest image," colors and shapes as they appear to normal visual perceivers. No color is a shape; but it is also true that there are no colored particulars without shapes, and no shaped particulars without colors. This is a point of phenomenology. One cannot see a colored particular without seeing something that has some shape or other, and vice versa. (And this is so even if the particular is an after-image.) But only some material things are minds. So we have a disanalogy. Wherever a color property is instantiated, a shape property is instantiated, and wherever a shape property is instantiated, a color property is instantiated. But it is not the case that wherever a physical property is instantiated a mental property instantiated. There are plenty of physical particulars that lack mental features even if it is true that everything with mental features also has physical features. Why the asymmetry? This needs to be explained.
Mental Properties as Emergent Properties
Assuming that all particulars are physical particulars -- that there are no unembodied or disembodied or possibly disembodied minds -- why do only some particulars have mental properties? Probably the most plausible thing to say is that only some physical systems are sufficiently complex to 'give rise' to mentality. This implies that mental properties are emergent: they are system features that are not reducible to or explicable in terms of the properties of the parts of the system even when their causal interactions are taken into account.
Bear in mind that not every system feature is emergent. Suppose a wall is made of 1000 piled stones and nothing else, each stone weighing one lb. It follows that the system -- the wall -- weighs 1000 lbs. But the property of weighing 1000 lbs., though a property of the whole and not of any part, is not an emergent property. For it is determined by the properties of the parts. In a more complicated system, the parts causally interact in significant ways. (The stones in the wall interact too, but in insignificant ways.) Think of a wrist watch. The property of showing high noon, though a system property, is not an emergent property because it is determined by the properties and causal interactions of the parts.
An emergent property is one that is irreducible to the properties and causal interactions of the items in its emergence base, but somehow emerges from that emergence base and remains tied to it. The notion of emergence is a curious and possibly incoherent one, combining as it does the notions of irreducibility and dependency. An emergent property is dependent in that (i) it cannot exist uninstantiated, and (ii) it cannot exist unless the emergence base is sufficiently complex, and will continue to exist only as long as the emergence base retains its 'sufficient complexity.' An emergent property is irreducible in that it cannot be accounted for in terms of the properties and interactions of the items in the emergence base. This suggests that emergent properties are real iff they induce causal powers in their possessors above and beyond the causal powers that are explicable in terms of the items in the emergence base.
My point is that if only some physical systems exhibit mentality, namely, those systems that manifest a high degree of (biological) complexity, then the mental properties of these systems must be emergent properties, properties that induce special causal powers in their possessors. But then we must ask what are the possessors of these emergent mental properties. The system as a whole, no doubt. But what does that mean? The mereological sum of the physical items that make up the system in question? But a mereological sum is too frail a reed to support a property. Indeed, some see no real distinction at all between a sum and its members. We need something more substantial to serve as support of mental properties. But I am at a loss to say what that more substantial something is.
The argument so far is as follows. The red ball analogy fails because only some physical particulars instantiate irreducibly mental properties. This is readily explainable if irreducibly mental properties are emergent properties. Emergent properties are system properties, properties of complex (biological) systems. But then the question arises as to what these emergent properties are properties of. They can't be properties of the parts of a system taken distributively any more than the property of weighing 1000 lbs. can be taken to be a property of the stones composing a wall taken distributively. So emergent properties are properties of wholes or collections of some sort. But this seems problematic.
For one thing, there are many mental properties had by one minded organism. I see a javelina; I hear it; I smell it. All in the unity of one consciousness. The mental properties are not just instantiated; they are co-instantiated, instantiated in or by one thing. If Manny sees, Moe hears, and Jack smells, it does not follow that there is one minded organism that does all three. So if mental properties are emergent system properties we need to know which one item it is that instantiates them and unifies them. The brain as a whole? What does that mean? No matter how we construe wholes, whether as mereological sums, mathematical sets ordered or unordered, aggregates, what-have-you, no whole is 'substantiatial' enough to unify the various mental properties that minded organisms exhibit.
It is also unclear how a mere collection could be the subject of experience. The subject of experience is not merely the support and unifier of mental properties; it is also that which is aware (whether intentionally or non-intentionally) in virtue of the instantiation of the mental propertiers. How could the subject of experience be a collection of objects?
So I remain in the dark as to what exactly property dualism could be if it is supposed to be a coherent position. What is it exactly that instantiates mental properties on this view?