Conclusion
“If the world is as described by the modern philosophy (or in a way not going beyond physics), we cannot conceive of it." I side with Hume and the Russellian Monists—and against causal structuralists—in affirming that conditional statement.
But should we then go on to affirm the antecedent or deny it? Here, I side with the Russellian Monists against Hume—the world has intrinsic properties after all, perhaps analogous to colors as naively conceived.16Notes
1 The following counterpart of the argument from 6 and 7 to 8 is valid in modal logic: (6') N(Bx & Ex → Cx v Sx); (7') N(Bx → ~Cx); therefore, (8') N(Bx & Ex → Sx). (6') would be delivered by ‘It is inconceivable2 that a body be extended, yet neither colored nor solid' (a possible reading of 6) together with the principle that what is inconceivable is impossible.And together with the converse principle that whatever is impossible is inconceivab^, (8') would deliver ‘It is inconceivab^ that a body be extended, yet not solid' (a possible reading of 8). But nothing plausible would deliver (7'), as I point out in the text.
2 Locke says he uses the term Solidity “because it carries something more of positive in it, than Impenetrability, which is negative, and is, perhaps, more a consequence of Solidity, than Solidity itself” (1975, 2.4.1, 123).
3 For more on these two varieties of skepticism, both of which Thomas Reid found in Hume, seeVan Cleve 2015, 53-56.
4 See Russell 1927 and the excerpts from Russell in Alter and Nagasawa 2015a.
5 But not logically inevitable unless (1) is read strongly as implying that physics ascribes no intrinsic and no categorical properties to things. It must be read as excluding the possibility, allowed by the twin tenets in (2), that every dispositional property is grounded in a categorical relational property and every relational property in an intrinsic dispositional property in an endlessly alternating downward sequence.
6 My own favorite argument for panpsychism proceeds from the need for simple substances to have intrinsic properties rather than from the need to solve the mind-body problem. It is an argument attributed by Kant to Leibniz and reconstructed in Van Cleve 1988.
7 Lewis's thesis is also more radical than Langton's insofar as it implies that in many cases we cannot know which of several candidate relations—not just which of several intrinsic properties—is instantiated by things.
8 The original presentation is Ramsey 1931; a good exposition is Psillos 2004. One of the artificialities of my toy example is that there is no sentence in the theory saying how the theoretical entities or properties are related to each other; to remedy that, we could add a sentence saying (for instance) that at certain distances, positives attract negatives.
9 For discussion of epistemological strategies that would let us know that one of the theories rather than the other is true despite their observational equivalence, see Schaffer 2004 (pro) and Locke 2009 (contra).
10 Some authors see Ramsey sentences as one way of articulating the “structure” that according to Russell is all that physics can tell us. See Psillos 2004 for critical discussion.
11 There is a serious typo in the version of Lewis's article in Braddon-Mitchell and Nola. In the fourth sentence of the second paragraph of section 4, the first occurrence of “F1” should be “F2.”
12 As it happens, Lewis denies haecceitism despite accepting quidditism; he devotes several paragraphs of 2009 to defending this asymmetry.
13 Quoted in Wood 1998, p. 31.
14 What manner of thing might the nonsolid item be? Two possibilities are places themselves in the philosophy of Newton and extended souls in the philosophy of Henry More.
15 Above, I characterized Hume's circle as defining solidity in terms of solidity, but this small circle follows from the larger circle (solidity in terms of bodies and bodies in terms of solidity) by transitivity.
16 A longer version of this chapter, containing among other things discussions of dispositional monism, naive realism, and the relations of bodies to places, is available on my USC website. I thank Matt Davidson, Janet Levin, and Adam Pautz for helpful discussion.
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