Property dualism
Property dualism describes a category of positions in the philosophy of mind which hold that, although the world is composed of just one kind of substance—the physical kind—there exist two distinct kinds of properties: physical properties and mental properties. In other words, it is the view that at least some non-physical, mental properties exist in, or naturally supervene upon, certain physical substances.
Substance dualism, on the other hand, is the view that there exist in the universe two fundamentally different kinds of substance: physical and non-physical, and subsequently also two kinds of properties which inhere in those respective substances. Both substance and property dualism are opposed to reductive physicalism. Notable proponents of property dualism include David Chalmers, Christof Koch, and Richard Fumerton. It became prominent in the final decades of the twentieth century and is now the leading alternative to physicalism.
Definition
Property dualism posits the existence of one material substance with essentially two different kinds of property: physical properties and mental properties. It argues that there are different kinds of properties that pertain to the only type of substance, the material substance: there are physical properties such as having colour or shape and there are mental properties like having certain beliefs or perceptions.Epiphenomenalism
is a position in the philosophy of mind on the mind–body problem. It holds that one or more mental states and their properties are by-products of the states of a closed physical system, and are not causally reducible to physical states. According to this view, mental properties are as such real constituents of the world, but they are causally impotent; while physical causes give rise to mental properties like sensations, volition, ideas, etc., such mental phenomena themselves cause nothing further - they are causal dead ends.The position is credited to English biologist Thomas Huxley, who analogised mental properties to the whistle on a steam locomotive. The position found a level of favor amongst some scientific behaviorists over the next few decades, which then dove in response to the cognitive revolution in the 1960s.
Epiphenomenal qualia
In the papers "Epiphenomenal Qualia" and "What Mary Didn't Know", Frank Jackson made the so-called knowledge argument against physicalism. The thought experiment was originally proposed by Jackson as follows:Jackson continued:
Other proponents
Saul Kripke
has a well-known argument for some kind of property dualism. Using the concept of rigid designators, he states that if dualism is logically possible, then it is the case.Criticism
In a short paper titled "Why I Am Not a Property Dualist", John Searle explains both why his own biological naturalism thesis is distinct from property dualism, as well as why he rejects the latter. He criticises property dualism for wanting to say that the mental and physical are primary ontological categories, the mental is irreducible to, or "over and above", the physical, and the mental and physical are not two separate substances, but are rather two properties of the same physical substance; he sees all three statements taken together as contradictory, and also as forcing the property dualist to face a dilemma between epiphenomenalism and causal overdetermination. According to Searle, the first two statements necessarily commit one to a Cartesian substance ontology, and so the property dualist adds the third statement in order to avoid the problems inherent in substance dualism, but this ends up introducing the aforementioned dilemma between epiphenomenalism and causal overdetermination. Property dualism is thus essentially substance dualism dressed up in the language of properties.Richard Rorty, in Chapter 1 of Philosophy and the Mirror of Nature, similarly criticises property dualism for essentially being substance dualism under a different name. He claims that a dualism of properties can simply reflect two different ways of talking about the same thing, namely the states or properties of a person, and even though people are typically incorrigible when talking about themselves using the phenomenal vocabulary, he believes that this could simply reflect an epistemic distinction rather than an ontological one. According to Rorty, the only way that the property dualist can maintain an ontological gap between the two properties is by hypostatising phenomenal properties into non-physical particulars which possess the property of being pure appearances. But then the property dualist starts to look like a substance dualist, since now there are two distinct property-bearing particulars rather than one particular with two properties.