Metaphysics: Free Will, Personal Identity & the Philosophy of Mind
Core Philosophical Problems
Course 3 · Chapter 4 · Metaphysics: Free Will, Personal Identity & the Philosophy of Mind
Free Will: Determinism, Libertarianism & Compatibilism
The universe is fully determined by prior causes, and this is genuinely incompatible with free will — so free will doesn't exist.
Free will is real, which means determinism must be false — genuine choice requires some real, causally undetermined gap.
Free will and determinism can coexist — genuine freedom just means acting on your own desires without external constraint, regardless of whether those desires were themselves determined.
Pierre-Simon Laplace's real 1814 thought experiment, from A Philosophical Essay on Probabilities: an intellect that knew every force in nature and the position of every particle at a single instant could, in principle, calculate the entire future and the entire past with perfect precision — the clearest possible statement of strict causal determinism. Laplace himself never actually called this intellect a "demon"; that vivid label was added later by others describing his idea.
Harry Frankfurt's real 1969 paper, "Alternate Possibilities and Moral Responsibility," challenges the assumption that moral responsibility requires being able to have done otherwise. His scenario: Jones is about to make a decision; an observer, Black, has secretly arranged to force Jones into a specific choice — but only if Jones shows signs of choosing differently. If Jones freely decides on that same choice anyway, Black never intervenes at all. Jones genuinely couldn't have done otherwise — Black's hidden mechanism guarantees the outcome — yet Jones still seems fully morally responsible for what he did, since he arrived at it entirely on his own.
Personal Identity
The Ship of Theseus is a real, genuinely ancient puzzle, recorded in Plutarch's Life of Theseus: Athenians preserved Theseus's ship for generations by replacing each decaying plank with new timber as it wore out. Once every original plank has eventually been replaced, is it still the same ship? Ancient philosophers themselves genuinely disagreed. Thomas Hobbes later deepened the puzzle further: what if all the discarded original planks were collected and reassembled into a second ship — which one, if either, is the "real" Ship of Theseus?
John Locke's own real thought experiment, from his Essay Concerning Human Understanding, imagines a prince's consciousness — his memories, his sense of self — transferred entirely into a cobbler's body, while the cobbler's own consciousness vanishes. Locke's real conclusion: everyone would say the prince, not the cobbler, now inhabits that body. Personal identity, on Locke's account, tracks psychological continuity — memory and consciousness — not the physical body or substance at all.
The Philosophy of Mind
Course 2 already covered this puzzle's own two real anchor points in depth: Descartes's substance dualism (Ch.2), with Princess Elisabeth of Bohemia's real interaction-problem objection, and Chalmers's real hard problem of consciousness (Ch.9). Since Descartes, two further contemporary positions have developed directly in response: physicalism holds that mental states simply are physical brain states, nothing more, avoiding dualism's interaction problem entirely by denying there are two substances to begin with; functionalism holds that a mental state is defined by what it does — its causal role, connecting inputs to outputs and other mental states — rather than what it's physically made of, leaving open, at least in principle, whether something non-biological could ever genuinely think.
| Free will position | Personal identity parallel | Mind position |
|---|---|---|
| Hard determinism | No persisting self at all (Hume's bundle theory) | Physicalism |
| Libertarianism | A persisting, non-physical soul (Descartes) | Substance dualism |
| Compatibilism | Continuity via psychological connection (Locke) | Functionalism |
Questions to Sit With
In the Frankfurt case, Jones couldn't have done otherwise, yet still seems responsible. Does that genuinely refute the idea that responsibility requires alternate possibilities, or does it just reveal a different, more subtle sense in which Jones "could" have chosen differently?
Hobbes's reassembled-planks version of the Ship of Theseus produces two competing candidates for the "real" ship. Which one would you actually pick, and what does your answer reveal about which notion of identity — form or matter — you find more convincing?
Functionalism suggests identity is about what a mental state does, not what it's made of. Could something entirely non-biological genuinely have a mind on this view — and if so, how would you ever be sure?
Quick Reference — Chapter 4
- Free will — hard determinism, libertarianism, compatibilism; Laplace's demon (1814, he never used the word "demon" himself); Frankfurt cases (1969) challenging the Principle of Alternate Possibilities
- Personal identity — the Ship of Theseus (Plutarch; extended by Hobbes's reassembled-planks version); Locke's prince and the cobbler — identity tracks psychological continuity, not the body
- Philosophy of mind — Descartes's dualism and Chalmers's hard problem (Course 2), plus physicalism and functionalism as contemporary alternatives
- The identity-over-time question now spans three real forms across this whole project: Heraclitus/Atman-anatta (Course 1), Hume's bundle theory (Course 2), and the Ship of Theseus/Locke (this chapter)