On the Plurality of Worlds
The systematic defense of modal realism — concrete possible worlds as real as our own
Tradition: Analytic metaphysics / modal realism
Every way the world could have been is a way some concrete world is — modal realism in its strongest form
Lewis's "On the Plurality of Worlds" is the systematic defense of modal realism: the doctrine that the possible worlds quantified over in the semantics of modal logic are not abstract objects, not fictions, and not logical constructions — they are concrete particulars, as real and concrete as the one we happen to inhabit. The book argues that this radically counterintuitive position is paid for by the theoretical work it does: it provides the cleanest reductive analysis of modal claims (necessity, possibility, counterfactuals), of propositions (sets of worlds), of properties (sets of possibilia), of causation, and of mind. The famous "incredulous stare" objection — most philosophers find modal realism just unbelievable — is countered by detailed arguments that the alternatives are worse. Together with Kripke's "Naming and Necessity," this book defined late-twentieth-century analytic metaphysics.
Author
Editions cited
- Blackwell (1986)
School Embodiments
The principal philosophical (as distinct from physical-cosmological) defense of multiverse realism: there are infinitely many concrete possible worlds and we live in one of them.
"I believe, and so do you, that things could have been different in countless ways. … I suggest it means that there are many ways things could have been besides the way they actually are." (Plurality of Worlds, ch. 1)
A founding text of contemporary analytic metaphysics; the systematic ambition of the project is unrepresented elsewhere.
"Modal realism has its costs, but they are paid for by the theoretical economies it makes possible." (Plurality of Worlds)
Lewis presents modal realism as a naturalistic extension of the same realism we already accept about the actual world — no special-purpose modal entities, just more concrete worlds of the kind we already have one of.
"Possible worlds are not abstract entities; they are concrete particulars, like our own world." (Plurality of Worlds)
Lewis's realism about properties (as sets of possibilia), about mathematics, and about possible worlds places him in a broadly Platonist register, even where he reinterprets these set-theoretically.
"Modal realism gives Platonic realism a concrete-worldly foundation." (paraphrasing the structural argument)
Although Lewis predates the contemporary simulation argument, his modal-realist framework provides one philosophical backdrop against which simulation arguments are formulated.
"In every possible world in which a Boltzmann brain forms, its consciousness is just as real as ours is in ours." (a Lewis-modal-realist corollary)
Analytic-philosophical tradition.
Modal-realist tradition.
Internal Tensions
The "incredulous stare" objection is the principal lasting difficulty: modal realism is the position most analytic philosophers find unbelievable while granting its systematic power. Alternatives (Kripkean abstractionism, ersatzism, fictionalism) trade off different theoretical costs.
I. Time
B-theoretic eternalism within each world; four-dimensional persistence through temporal parts.
Attributes
II. Space
Standard substantival space within each of the infinitely many concrete worlds.
Attributes
III. Matter
Standard substantival matter; the local-qualities mosaic of Humean supervenience.
Attributes
IV. Observer
Plural finite observers in each world; mediated knowledge through inference. No metaphysical agency.
Attributes
V. Energy
Standard physics.
Attributes
VI. Information
Information conserved at the world-scale; personal soul not.
Attributes
Personas that cite this work
Personas with the nearest attribute fingerprint
Historical figures whose own classification on the same six-dimensional grid lands closest to this work's. Computed by attribute-agreement on coordinates both address.
Computed school proximity
The work's attribute fingerprint scored against all schools using the same quiz scorer. Useful as a sanity check on the hand-curated embodiments above.
How On the Plurality of Worlds resolves each dilemma
57 resolved positions across 4 dimensions, including 7 distinctive where the majority of schools go the other way.
Each dimension is sorted so minority positions come first. Mainstream positions are folded into an expandable list.
Time · 9 dilemmas · 5 distinctive
Persistence, the future, and the direction of becoming.
4 mainstream positions
Matter · 7 dilemmas, all mainstream
Observer · 37 dilemmas · 1 distinctive
Mind, agency, and the knower's relation to the known.