It is a peculiar feature of Reasons and Persons that almost everyone has heard of the teletransporter case and almost no one remembers what Parfit thought it showed. The popular telling treats the book as a kind of metaphysical horror story: you step into the machine, your body is destroyed, a copy is reconstituted on Mars, and either (a) the copy is you or (b) you are dead and a stranger now lives your life. The book does not answer this question. That refusal is the whole point.
What Parfit was after
Parfit’s strategy was to assemble cases — teletransport, fission, gradual brain replacement — in which the standard criteria for personal identity (psychological continuity, bodily continuity, soul-stuff) come apart in ways our intuitions cannot smoothly track. Faced with the fission case, where two equally good continuants both walk out of the lab, we cannot say both are you (you can’t be in two places) and we cannot non-arbitrarily say neither is. Identity is the wrong notion to be carrying around.
What matters in survival is not identity but Relation R: psychological connectedness and continuity, with the right kind of cause.
Why this matters off the page
If Parfit is right, a great deal of our practical reasoning is built on a confusion. Prudential concern for our future self begins to look more like a kind of generalized concern for whoever stands in Relation R to us — which, by degrees, includes other people. The wall between self-interest and altruism gets thinner. This is not a rhetorical flourish; it changes how you should think about saving, about long-term commitments, about end-of-life decisions.
The objection I keep returning to
Critics — Schechtman, Korsgaard, Velleman — have pressed the worry that Parfit gives us metaphysics where we needed a self. The narrative self, the agential self, the one that endorses what it does, is left behind in the fission room. I am sympathetic to the worry. But I think Parfit’s view survives it, in this sense: even granting that we need a robust agential self for ethics and politics, that self is built from the materials of Relation R. It is not a further fact lurking behind them.
The book’s most underrated sentence is in §95: “My life seemed like a glass tunnel, through which I was moving faster every year, and at the end of which there was darkness.” What changes after Parfit, he says, is that the glass walls are gone. Other lives are now nearer. That is a strange, beautiful place for a metaphysics book to land.
The fission case still bothers me. If R is what matters and both continuants have R, why does losing the identity-relation feel like a loss at all?
Schechtman’s narrative critique deserves more space here. Curious what you think of her recent work on cluster accounts.