1 Thanks to Torin Alter, Andrew Bailey, Phil Kremer, Antonia LoLordo, William Seager, Mark Walker and the audiences of the APA Pacific Division and the CPA Halifax, for discussion on an earlier version of the paper. Special thanks to the anonymous reviewers for their sharp and useful comments.

2 Chalmers, David J. The Conscious Mind: In Search of a Fundamental Theory (New York: Oxford University Press 1996)Google Scholar

3 See Melnyk, Andrew. ‘Physicalism Unfalsified: Chalmer's Inconclusive Conceivability Argument’ in Physicalism and Its Discontents, Gillett, Carl and Loewer, Barry eds. Cambridge: Cambridge University Press 2001.Google Scholar

4 Premise (ii) If I can conceive of these worlds, then (defeasibly) these worlds are logically possible, is in my mind preferable to this counterpart (ii*) If the zombie world is ideally conceivable then the zombie world is possible. Talk of ‘ideal’ conception, like ideal epistemic situations generally, tend to be difficult to explicate without circularity, and they are nothing like idealizations in scientific theory.

5 I say ‘modal or causal’ to note that I do not wish to commit myself to the existence of fundamental causal dependencies. There may be law, or counterfactual dependence, without causation relating the most fundamental entities. Those who assume that the basic relations will be causal or that the fundamental laws will be causal laws, hold a particularly strong form of physicalism. But causation is an old and contested metaphysical subject — and the phenomena of causation might not be in need of saving. There may be no need to understand the fundamental laws as causal — and if the failures to analyze causation successfully lead to pessimism regarding its existence, we may have some reason to doubt that they are causal. However, my arguments should work for those who believe that causation is found between the fundamental physical properties.

6 However, Jackson's knowledge argument and arguments from multiple realizability do not rely on the logical possibility of zombie worlds, so they will remain unaffected by the argument of this paper.

7 See Ellis, Brian The Philosophy of Nature: A Guide to the New Essentialism (Montreal: McGill Queens University Press 2002).CrossRefGoogle Scholar

8 Kim, Jaegwon Physicalism, or Something Near Enough (Princeton, NJ: Princeton University Press 2005);Google Scholar Mind in a Physical World: An Essay on the Mind-Body Problem and Mental Causation, (Cambridge, MA: Bradford, MIT Press 1998).

9 As stated, my worlds have only two physical properties and two objects and that may seem more confusing than simplifying, after-all, actual conscious persons are made of many parts and appear to have many physical properties. On the other hand, a ‘unified field theory’ might have ontological commitment to only one physical field and the only individuals of metaphysical worth might be only space-time points. In short, feel free to drop the ‘simplifying’ assumption.

10 Whether the fundamental laws are causal or not, is not something that I wish to presuppose as essential to physical properties. But this is an epistemological consideration due to our not yet knowing how best to articulate the basic laws. If they are indeed causal, as many metaphysicians assume, then my nomological essentialism will be a causal-nomological essentialism. However, I am skeptical that the fundamental laws count as causal.

11 There are several objections to the thesis based on the proliferation of necessities. Worlds must share all the same physical properties and laws or be entirely alien in their contents and physical possibility ‘becomes’ a species of logical possibility. But I think biting these bullets is to bite blanks, so no intellectual harm is done.

12 See Bohm, David Causality and Chance in Modern Physics (Philadelphia: University of Pennsylvania Press 1957).Google Scholar

13 See Sydney, Shoemaker Identity, Cause and Mind: Philosophical Essays (London: Cambridge University Press 1984);Google Scholar Achinstein, Peter ‘The Identity of Properties,’ American Philosophical Quarterly 11 (1974) 257–76.Google Scholar

14 This appears to be a very popular assumption among physicalists and dualists alike: popular for dualists who wish to contrast the essentially causal nature of the physical with the allegedly non-causal nature of the qualitative aspect of consciousness, and popular with physicalists who wish to find a ground or mechanism for causal relations between supervenient events or property instances.

15 I shall return to this point below. For example, if physical properties have causal capacities contingently (i.e. there are worlds in which physical properties occur, but don't share the same laws of nature as ours, hence they have either different causal capacities or no causal capacities), then they are not so different from those who claim that phenomenal properties, when causally efficacious, are so only contingently. The typical contrast drawn between phenomenal and physical properties is that (i) the phenomenal is non-relational but physical properties are not, and (ii) the phenomenal is qualitative, but physical properties are not, and (iii) phenomenal properties are epistemically immediate, but physical properties are not.

16 I have no sympathy for the notion that consciousness is not essentially causal. The essential activity of soul, pneuma, life, thought, Fichtean absolute self, or whatever etc., is remarked upon by many authors. They might be wrong, but it is very hard to believe, given the history of these ideas, that the meaning, or intension of these terms and concepts doesn't involve ‘activity’ or causation. Keeping the history of our concepts in mind we might go so far to claim that those who deny efficacy to these properties should be considered closet eliminativists, for they deny something that is steadfastly maintained to be true. However, having said that, let me be more careful. Not all mental items have been thought to be essentially active: Berkeley takes ideas to be passive. With this in mind, it would not be conceptually outrageous to suggest that qualia are not essentially active, even if self, soul, pneuma and their 21st century counterparts are so considered.

17 For discussion of the exclusion argument see, among many others, Garrett, Brian Jonathan ‘Pluralism, Causation and Overdetermination,’ Synthese 116, 3 (1998)Google Scholar and ‘Defending Non-Epiphenomenal Event Dualism,’ Southern Journal of Philosophy 38, 3 (2000 ); Sturgeon, Scott ‘Physicalism and Overdetermination,’ Mind 107 (1998) 411–31.CrossRefGoogle Scholar

18 I take it that this logical possibility will not be easily denied, (unless we are causal essentialists.) Why couldn't there be worlds in which P is nomologically incompatible with P* even though in worlds with our distinct laws P* depends on P. David Lewis holds to recombination, i.e. that any combination of a possible with another yields a further possibility, and in his Humean metaphysics this should be acceptable.

19 It may be that science cannot give a full account of all the world's properties because some of those properties are not epistemically accessible to human minds. I believe that is a plausible epistemological claim — but the claim discussed above is that science gives incomplete explanations of real properties even though we have no epistemic barriers like that to overcome in our science.

20 It should be noted that I am not committed to the view that humans can know everything about nature. The point is, rather, this: science's goal is to describe and explain all the capacities of a property to effect change. Whether all these capacities are epistemically accessible given our mental capacities is an open question. The debate above is over a science that did succeed. Would it be complete?

21 When a property's capacity is triggered resulting in the realization of a further property this will be limited to certain contexts or situations. Thus salt has the capacity to dissolve in water, and salt immersed in water will dissolve in certain circumstance, e.g. if the water is not already saturated with salt. The zombie world is one which is allegedly physically indiscernible from the actual world, so the contexts are intended to be identical. Thus I ignore the complications regarding contexts that one would normally mention when discussing capacities and dispositions.

22 Again, there are no further physical conditions to block the exercise of the causal capacity of F, because we are looking at worlds physically indiscernible with the actual world in which we assumed that F has been triggered.

23 Thanks to Torin Alter for this objection to an older draft of this paper.

24 Believing in essential properties, whether essential dispositional properties or not, is controversial and I offer no defense here for assuming that there are such properties. The issue here is whether there is a reason to distinguish, for the basic properties, causal capacities that are essential from those that are not.