Posted by: Xhyra Graf | 28 January 2007

Property Dualism

2.2 Property Dualism

Whereas predicate dualism says that there are two essentially different kinds of predicates in our language, property dualism says that there are two essentially different kinds of property out in the world. Property dualism can be seen as a step stronger than predicate dualism. Although the predicate ‘hurricane’ is not equivalent to any single description using the language of physics, we believe that each individual hurricane is nothing but a collection of physical atoms behaving in a certain way: one need have no more than the physical atoms, with their normal physical properties, following normal physical laws, for there to be a hurricane. One might say that we need more than the language of physics to describe and explain the weather, but we do not need more than its ontology. There is token identity between each individual hurricane and a mass of atoms, even if there is no type identity between hurricanes as kinds and some particular structure of atoms as a kind. Genuine property dualism occurs when, even at the individual level, the ontology of physics is not sufficient to constitute what is there. The irreducible language is not just another way of describing what there is, it requires that there be something more there than was allowed for in the initial ontology. Until the early part of the twentieth century, it was common to think that biological phenomena (‘life’) required property dualism (an irreducible ‘vital force’), but nowadays the special physical sciences other than psychology are generally thought to involve only predicate dualism. In the case of mind, property dualism is defended by those who argue that the qualitative nature of consciousness is not merely another way of categorizing states of the brain or of behaviour, but a genuinely emergent phenomenon.

5.1 The Queerness of the Mental

Mental states are characterised by two main properties, subjectivity, otherwise known as privileged access, and intentionality. Physical objects and their properties are sometimes observable and sometimes not, but any physical object is equally accessible, in principle, to anyone. From the right location, we could all see the tree in the quad, and, though none of us can observe an electron directly, everyone is equally capable of detecting it in the same ways using instruments. But the possessor of mental states has a privileged access to them that no-one else can share. That is why there is a sceptical ‘problem of other minds’, but no corresponding ‘problem of my own mind’. This suggests to some philosophers that minds are not ordinary occupants of physical space.

Physical objects are spatio-temporal, and bear spatio-temporal and causal relations to each other. Mental states seem to have causal powers, but they also possess the mysterious property of intentionality — being about other things — including things like Zeus and the square root of minus one, which do not exist. No mere physical thing could be said to be, in a literal sense, ‘about’ something else. The nature of the mental is both queer and elusive. In Ryle’s deliberately abusive phrase, the mind, as the dualist conceives of it, is a ‘ghost in a machine’. Ghosts are mysterious and unintelligible: machines are composed of identifiable parts and work on intelligible principles. But this contrast holds only if we stick to a Newtonian and common-sense view of the material. Think instead of energy and force-fields in a space-time that possesses none of the properties that our senses seem to reveal: on this conception, we seem to be able to attribute to matter nothing beyond an abstruse mathematical structure. Whilst the material world, because of its mathematicalisation, forms a tighter abstract system than mind, the sensible properties that figure as the objects of mental states constitute the only intelligible content for any concrete picture of the world that we can devise. Perhaps the world within the experiencing mind is, once one considers it properly, no more — or even less — queer than the world outside it.

5.2 The Unity of the Mind

Whether one believes that the mind is a substance or just a bundle of properties, the same challenge arises, which is to explain the nature of the unity of the immaterial mind. For the Cartesian, that means explaining how he understands the notion of immaterial substance. For the Humean, the issue is to explain the nature of the relationship between the different elements in the bundle that binds them into one thing. Neither tradition has been notably successful in this latter task: indeed, Hume, in the appendix to the Treatise, declared himself wholly mystified by the problem, rejecting his own initial solution (though quite why is not clear from the text).

5.2.1 Unity and Bundle Dualism

If the mind is only a bundle of properties, without a mental substance to unite them, then an account is needed of what constitutes its unity. The only route appears to be to postulate a primitive relation of co-consciousness in which the various elements stand to each other.

There are two strategies which can be used to attack the bundle theory. One is to claim that our intuitions favour belief in a subject and that the arguments presented in favour of the bundle alternative are unsuccessful, so the intuition stands. The other is to try to refute the theory itself. Foster (1991, 212-9) takes the former path. This is not effective against someone who thinks that metaphysical economy gives a prima facie priority to bundle theories, on account of their avoiding mysterious substances.

The core objection to bundle theories (see, for example, Armstrong (1968), 21-3) is that, because it takes individual mental contents as its elements, such contents should be able to exist alone, as could the individual bricks from a house. Hume accepted this consequence, but most philosophers regard it as absurd. There could not be a mind that consisted of a lone pain or red after-image, especially not of one that had detached itself from the mind to which it had previously belonged. Therefore it makes more sense to think of mental contents as modes of a subject.

Bundle theorists tend to take phenomenal contents as the primary elements in their bundle. Thus the problem is how to relate, say, the visual field to the auditory field, producing a ‘unity of apperception’, that is, a total experience that seems to be presented to a single subject. Seeing the problem in this way has obvious Humean roots. This atomistic conception of the problem becomes less natural if one tries to accomodate other kinds of mental activity and contents. How are acts of conceptualising, attending to or willing with respect to, such perceptual contents to be conceived? These kinds of mental acts seem to be less naturally treated as atomic elements in a bundle, bound by a passive unity of apperception. William James (1890, vol. 1, 336-41) attempts to answer these problems. He claims to introspect in himself a ‘pulse of thought’ for each present moment, which he calls ‘the Thought’ and which is the ‘vehicle of the judgement of identity’ and the ‘vehicle of choice as well as of cognition’. These ‘pulses’ are united over time because each ‘appropriates’ the past Thoughts and ‘makes us say “as sure as I exist, those past facts were part of myself”. James attributes to these Thoughts acts of judging, attending, willing etc, and this may seem incoherent in the absence of a genuine subject. But there is also a tendency to treat many if not all aspects of agency as mere awareness of bodily actions or tendencies, which moves one back towards a more normal Humean position. Whether James’ position really improves on Hume’s, or merely mystifies it, is still a moot point. (But see Sprigge (1993), 84-97, for an excellent, sympathetic discussion.)


Robinson, Howard, “Dualism”, The Stanford Encyclopedia of Philosophy (Fall 2006 Edition), Edward N. Zalta (ed.), URL =



  1. […] Stance: I am a property dualist […]

  2. […] One version of the property-based problem arises immediately for those philosophers who believe that, even if mental substances are physical, mental properties are not. “Property dualism” has several contemporary defenders, including David Chalmers (1996) and at one time Frank Jackson (1982, 1986; but see his 1998, forthcoming). For the property dualist, mental properties — and here the mental properties taking center stage are the phenomenal properties of conscious experience — are sui generis, not reducible to the dispositional or structural properties recognized by the physical sciences (see dualism). […]


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