Philosophy 596B: Metaphysics

Mind and Modality

David Chalmers



When one thinks about the mind-body problem, or about metaphysics more generally, one is quickly led into thinking about possibility and necessity.  Materialism, for example, is naturally understood as making a modal claim -- the physical facts necessitate all the facts -- and questions about the truth of materialism turn on deep questions about the nature of possibility and necessity.  How extensive is the space of possible worlds?  What is the relationship between conceivability and possibility?  How can we have cognitive access to matters of possibility and necessity?  In this course, we will use modal considerations in the philosophy of mind as a route into the thickets of modality.

We will start by considering some modal arguments against materialism, and by looking at the varieties of possibility and necessity.  Then we will concentrate on the phenomenon of a posteriori necessity, and try to understand its roots (with a detour into two-dimensional semantics, and into the logic of conditionals), and we will try to come to grips with the philosophical concept of a possible world.  In the second half of the course, we will concentrate on the relationship between conceivability and possibility, and more generally on the relationship between the epistemology and the metaphysics of modality; and we will look into implications for the philosophy of mind and for metaphysics more generally.  We will read recent works by a number of philosophers on these issues, within metaphysics, the philosophy of language, and the philosophy of mind.  Along the way, I will present portions of some work in progress on the general theme of "modal rationalism".


The Lewis book is out of print, unfortunately, so I will include some of it in the reading packet (which won't be needed for a few weeks; I'll let you know about availability as the time approaches).  Where articles are available on the web, I've indicated this below.  All the web articles should be accessible from my page of online papers on consciousness (especially the section on materialism and modality).

You may also want to consult my bibliography of contemporary philosophy of mind (especially section 1.3).

Much of the course will loosely follow the structure of my Princeton lectures on Mind and Modality (especially the first two lectures),

Mailing list

I will set up a mailing list,, for class discussion.  This will be the main locus of the course while I am in Australia, and will continue to play a role when I return. Everyone will be expected to make reasonably regular contributions to this list (at least one reasonably substantial posting every week), discussing issues arising from the readings, from class discussion, and from the mailing list itself. Discussion from the mailing list is retrospectively included with the associated weeks below.


Here is a very approximate week-by-week plan for the course.  The correspondence between topics here and weeks will probably be loose.  In the first few weeks in particular, things will be done somewhat differently to accommodate the electronic format.

1. Metaphysics and Modality

Varieties of possibility and necessity.  Conceptual, metaphysical, natural possibility; a priority; analyticity.  The importance of modality in metaphysics.  A sampling of modal arguments in metaphysics (causation, external reality, morality, intentionality, consciousness).  Modal definitions of materialism.

Week 1 discussion

2. Epistemic Arguments Against Materialism.

Conceivability arguments: the possibility of disembodiment (Descartes), of zombies, of inverted spectra.  Epistemic arguments: Jackson's knowledge argument, etc.  Conceptual analysis of phenomenal concepts.  Objections.  Type-A and type-B materialism.

Week 2 discussion

3. Naming and Necessity

Kripke's Naming and Necessity.  The modal argument for rigid designation and a posteriori necessities.  The epistemic argument against descriptive theories of reference.  Names and natural kind terms.  Application to metaphysical issues.

Week 3 discussion

4. The 2-D account.

The two-dimensional account of a posteriori necessity.  Primary and secondary intensions.  Two notions of necessity.  Link to apriority. Translation of Kripke's main theses into two-dimensional terms. Related ideas (Kaplan, Stalnaker, etc).

Week 4 discussion

5. The Tyranny of the Subjunctive.

The different behavior of subjunctive and indicative conditionals in the analysis of possibilities.  Links to two-dimensional semantics. The implicit dominance of the subjunctive in contemporary analyses of necessity.  How philosophy would look with indicatives instead.  The analysis of subjunctives and indicatives.  Epistemic vs. subjunctive possibility.

Week 5 discussion

6. Applying the 2-D account to the anti-materialist argument.

Type-B materialism: relying on a posteriori necessity to save the materialist.  Application of the two-dimensional analysis of a posteriori necessity to this position.  From an epistemic gap to an ontological gap?  Loopholes.

Week 6 discussion

7. Materialism and the Metaphysics of Modality (Strong Necessities).

The type-B materialist's escape route: strong necessities.  Are there strong necessities?  What do they involve?  Possible examples and explanations.

Week 7 discussion

8. Does Conceivability Entail Possibility?

Varieties of conceivability: prima facie vs. ideal, primary vs. secondary, positive vs. negative, etc.  Possible counterexamples to the conceivability/possibility link.

Week 8 discussion

9. Modal Rationalism and the Scrutability of Truth

Varieties of modal rationalism.  Three loopholes: strong necessities, inscrutable truths, open inconceivabilities.  The analysis of inscrutability.  Links to inscrutability of reference (Quine, Putnam, Benacerraf).  Possible examples: inscrutable mathematical truths, epistemic theory of vagueness, etc.  Arguments against inscrutability?

Week 9 discussion

10. Cosmic Hermeneutics

Are all truths entailed a priori by the microphysical (plus phenomenal) truths?  Link to inscrutability and modal rationalism. Arguments pro and con.

Week 10 discussion

11. Constructing Possible Worlds

What is a possible world?  Concrete vs. "ersatz" conceptions of possible worlds.  Constructing "ersatz" worlds.  Constructing conceivable worlds, handling epistemic vs. subjunctive possibilities and two-dimensional semantics, etc.

Week 11 discussion

12. Modal Monism and Modal Dualism

The argument for modal rationalism.  Do strong necessities commit one to modal dualism?  Should there be just one modal primitive? Constitutive links between modal and rational notions.  Handling tricky cases, e.g. haecceities.

Week 12 discussion

13. The Components of Content

Wide content and narrow content.  Using two-dimensional semantics to give an account of narrow content.  Application to the explanation of behavior, to the semantics of belief ascription, and to belief puzzles. Objections and subtleties.

Week 13 discussion

14. Further Directions

Hyperintensionality and the analysis of epistemic possibility.  The theory of concepts, meaning, and understanding.  Realism and anti-realism.

15. From Mind to Modality and Back Again

Where are we left in the philosophy of mind?  The menu of options re the metaphysics of consciousness.  The analysis of mental content. Links between consciousness and content?


The major item for assessment will be a paper due at the end of term. There may also be some smaller written assignments along the way, and student presentations in class.  All students are expected to participate in class discussion (both online and in person).

Mailing list

I will set up a mailing list,, for class discussion.  Everyone will be expected to make reasonably regular contributions to this list (at least one reasonably substantial posting every week), discussing issues arising from the readings, from class discussion, and from the mailing list itself.