The Possible & the Necessary

Eight steps into modality: what could have been, what must be, and whether other worlds are real.

A course on the thought of Metaphysics.

Course outline

1. Could It Have Been Otherwise? — The modal intuition and its first dangers. Some things must be, some could have been otherwise — but is the future already fixed? Aristotle's sea-battle opens the problem of necessity, contingency…
2. Truths of Reason, Truths of Fact — Leibniz's foundational division: necessary truths of reasoning (whose opposite is a contradiction) vs contingent truths of fact (grounded in the principle of sufficient reason). The threat that the…
3. Possible Worlds & the Best of All — Leibniz's great picture: in God's understanding lie infinitely many possible worlds, complete and compossible alternatives; by the principle of the best, God actualizes the one with the most…
4. Is Necessity in the World, or in Us? — Kant relocates necessity. The analytic/synthetic and a priori/a posteriori distinctions; necessity and strict universality as the marks of a priori knowledge; modality…
5. Naming and Necessity — Kripke's revolution. Names are rigid designators — they pick out the same thing in every possible world — and so identity statements between names (Hesperus = Phosphorus) and theoretical identities…
6. Are Possible Worlds Real Places? — Lewis's modal realism: the other possible worlds are not abstractions or ways God imagines things — they are real, concrete universes, as real as ours, just spatiotemporally and causally isolated…
7. Worlds Without the Worlds — The respectable alternative to Lewis: actualism. Possible worlds are abstract objects — maximal possible states of affairs — and only the actual world is concrete. Transworld identity and essences.…

Part of the Simposeum course library.