Suggested Topics

1. Consider one of the issues debated between Carnap and Quine, and discuss Lewis’s position on the issue, with an eye towards showing how he responds to and tries to resolve their debate. I have claimed generally that he wants to defend what he takes to be some core part of Carnap’s view, while at the same time agreeing with much of Quine’s arguments. You may or may not want to agree with me on that. Examples of debated topics (all related to each other, of course):
   1. The nature of and/or need for “ontological commitment.” Must I decide what (kinds of) things I take to really exist? How can or should I make that decision? Can you tell, empirically, what decision I have made? Can I have made the decision implicitly, without conscious awareness of what I was doing, and if so how can it still be called a “decision”? (Most relevant texts: “Empiricism, Semantics and Ontology”; “On Carnap’s Views on Ontology”; “reply to Quine’s ‘Carnap and Logical Truth’”; Introduction to Philosophical Papers; “Holes”; “Languages and Language”; “Noneism or Allism?”; On the Plurality of Worlds 2.1, 2.8.)

   2. Reduction. To what extent can we eliminate some part of our vocabulary in favor of some other, more fundamental part? Why would we want to do that? What makes the more fundamental part more fundamental? Must there be a unique way to carry out the reduction? Or in general: what kind of existence and uniqueness conditions does the reduction rest on, if any, and why or when are we justified in taking it that such conditions hold? (Most relevant texts: Aufbau; “Two Dogmas” §5; “New Work,” especially the sections titled “ONE OVER MANY” and “MINIMAL MATERIALISM”; “How to Define Theoretical Terms”; “Holes”; “Counterpart Theory.”)

   3. Meaning. What (if anything) makes linguistic signs meaningful? What, if anything, makes it a fact, either true or false, that a certain string of signs (i.e., string of sign types?) has a particular extension and/or intension? What role is played, or might be played, by the mental states of speakers? By conventions? By metaphysical truths? You may want to distinguish between the meaning of whole sentences and the meaning of subsentential constituents; also, between the meaning of empirical terms or sentences and the meaning of terms or sentences which are not empirical. (Most relevant texts: “Meaning and Synonymy in Natural Languages”; “Ontological Relativity”; “Languages and Language”; “Radical Interpretation”; “Noneism or Allism?”; “New Work,” especially the section titled “THE CONTENT OF LANGUAGE AND THOUGHT”; “Putnam’s Paradox.”)

2. What is Lewis’s overall account of the nature of philosophical argument – its rules, advantages and disadvantages, and ends or goals? Try to put together some, at least, of the pieces. For example: the lack of “knockdown” arguments; the fact that such arguments “would not be nice,” even if they were available; the role of “ontic” disagreement (is this just one example, or is it somehow the essential topic of philosophical dispute?); the supposed commitment of the philosophy department, among others, to the advancement of knowledge; the “tacit treaty” between schools of philosophy (that is, between the schools of philosophy that agree to regard each other as “respectable,” rather than “ratbag”); the process of getting someone to presuppose parts of your position, fairly or unfairly (is the fair way better, and why?); the distinction between terminological (a.k.a. “semantic”) disputes and other disputes, along with the claim that both types of dispute are important. (Most relevant texts: Introduction to Philosophical Papers; “Holes”; “Scorekeeping”; “Academic Appointments”; “Noneism or Allism?”; On the Plurality of Worlds 2.8.)

3. Lewis’s philosophy of science: what is it, and is it sufficient and satisfactory? There are a lot of possible sub-topics here. For example:
   1. The problems of induction and/or “scientific realism.” Why, according to Lewis, should I base any beliefs about the actual world on my empirical evidence, if I at the same time acknowledge that, at some possible world, an exact duplicate of me who draws the same conclusions (or at least, does all the intrinsic parts of drawing those conclusion) is entirely mistaken? (For example: there is an exact duplicate of me which is the only thing in its world; there is a world with an initial segment that duplicates the initial segment of ours up until just the present instant, but which thereafter violates all of our physical laws.) (Most relevant texts: On the Plurality of Worlds, 1.3, 1.8, 2.4, 3.2, especially the part about alien properties, beginning p. 158; “New Work,” especially the sections titled “DUPLICATION, SUPERVENIENCE, AND DIVERGENT WORLDS” and “MINIMAL MATERIALISM”; “Causation”; “How to Define Theoretical Terms,” especially the part towards the end about sense and denotation, starting p. 435 in the version up on eCommons.)

   2. The problem of theoretical and/or unobservable entities. According to Lewis, when should we believe that such things exist? When should we stop believing that they exist (e.g., phlogiston, caloric, ether, fire)? What risks of error do we run, either way? What role could so-called crucial experiments play in making a (rational) decision? What about the discovery of a possible reduction? (On the Plurality of Worlds, 2.4, 2.8; “How to Define Theoretical Terms”; “New Work,” especially the section titled “MINIMAL MATERIALISM”; “Noneism or Allism?”.)

   3. More generally, the issue of reductionism (and/or related questions about the mind–body relation) could be considered from this point of view, rather than with specific reference to the Carnap–Quine debate. What is happening, according to Lewis, when we reduce one theory to another? Why do that? What, if any, are the ontological presuppositions or ontological implications? (If you are interested specifically in the mind–body issues, you may want to see “Counterparts of Persons and Their Bodies”, and/or “Mad Pain and Martian Pain”.) (Most relevant texts: “How to Define Theoretical Terms”; “New Work,” especially the sections titled “ONE OVER MANY” and “MINIMAL MATERIALISM”; “Holes”; “Counterpart Theory.”)

   4. The nature of space and time. What makes spatiotemporal relations especially important, and why? The fact that they, or something like them, are used to individuate worlds, gives them a very special part in Lewis’s ontology. That part is obvious, but it’s worth discussing how special role can be motivated. Why does Lewis think it plausible that we could understand “actual” to mean, roughly, “standing in some spatiotemporal relation to ourselves”? (Why is that better than, for example, “standing in some causal relation to ourselves”?) Whatever the answer, you could try to relate it somehow to typical problems about space and time in philosophy of science. For example: must the world have some determinate geometry, and if so how could we know (or at least have some evidence as to) which geometry it is? Must, or might, there be such a thing as absolute space, absolute motion and absolute rest? (That is, you might try to figure out how Lewis must answer such a question, and whether he would think the answer is part of the benefit of his view, or, on the contrary, is part of the “price” we must pay for holding his view.) (Most relevant texts: On the Plurality of Worlds, 1.6, 1.8, 2.1; “Causation”; “How to Define Theoretical Terms”; “New Work,” especially the sections titled “DUPLICATION, SUPERVENIENCE, AND DIVERGENT WORLDS” and “MINIMAL MATERIALISM.”)

4. Lewis officially disclaims any ambition to compare his position to Leibniz’s. If you know something about Leibniz, you may want to fill in the missing comparison. Leibniz holds that the actual world is different from all other possible worlds in (at least) two ways: (a) is it actual; (b) it is optimal. Also, he holds that there is a necessary existent (“God”), and that both the possibility of all possible worlds and the actuality of the actual one depend causally (in some sense of causation!) on the (necessary) nature of that necessary existent. Also, he hold that apparently external relations generally, and spatiotemporal relations in particular, actually all supervene on internal relations of representation between monads: if monad A is spatially near to monad B, for example, then an intrinsic duplicate of A could not be spatially distant from an intrinsic duplicate of B. Why does, or why can, Leibniz hold these things while Lewis does not? What is the fundamental disagreement between them? Also: how does Leibniz fit, or not fit, into the types of “ersatzism” discussed by Lewis in chapter 3 of On the Plurality of Worlds? (Most relevant texts: almost everything is relevant, but I guess especially On the Plurality of Worlds, 1.6, 1.8, 2.1, 3.1–2, 4.1–3, as well as other sections that were not assigned, especially the remainder of ch.’s 3 and 4. From Leibniz, you would want to look especially at the parts of the Monadology and the “Discourse on Metaphysics” having to do with contingent and necessary truths and the nature of space, extension, and body, beyond that a lot of things could be relevant.)