- Philo of Alexandria, in De aeternitate mundi 48 (SVF ii. 397), gives the following brief and notoriously cryptic account of a puzzle about personal identity created by the Stoic philosopher Chrysippus:
- Chrysippus, the most distinguished member of their school, in his work On the Growing [Argument], creates a freak of the following kind.
- Having first established that it is impossible for two peculiarly qualified individuals to occupy the same substance jointly,
- he says: ‘For the sake of argument, let one individual be thought of as whole-limbed, the other as minus one foot. Let the whole-limbed one be called Dion1, the defective one Theon. Then let one of Dion’s2 feet be amputated.
- The question arises which one of them has perished, and his claim is that Theon is the stronger candidate.
- These are the words of a paradox-monger rather than of a speaker of truth. For how can it be that Theon, who has had no part chopped off, has been snatched away, while Dion3, whose foot has been amputated, has not perished?
- ‘Necessarily’, says Chrysippus. ‘For Dion4, the one whose foot has been cut off, has collapsed into the defective substance of Theon. And two peculiarly qualified individuals cannot occupy the same substrate. Therefore it is necessary that Dion5 remains while Theon has perished.’
- Perhaps the most widely accepted interpretation of this passage is that offered by "Sedley (David) - The Stoic criterion of identity" in 1982. In this paper, I will offer an interpretation that leaves the most important features of Sedley’s account intact, chief among which is his view on the basic purpose of the puzzle. Like Sedley, I take the fact that the puzzle appears in a work called On the Growing Argument to indicate that it is a rejoinder to, and indeed a reductio ad absurdum of, the Growing Argument. Where I diverge from Sedley’s approach, I do so to shore it up against certain objections to which I think it is vulnerable. My chief concerns are to achieve a better fit with the text, and to ensure that since we view the puzzle as a reductio ad absurdum, we do not take Chrysippus to be deducing a contradiction by means of premisses extrinsic to the Growing Argument. Otherwise, Chrysippus’ reductio ad absurdum would fail in its purpose of showing that the Growing Argument is internally inconsistent.
- I also follow Sedley on two other significant interpretative points.
- First, I agree that since, from at least Chrysippus’ point of view, the puzzle runs up against the principle that ‘two peculiarly qualified individuals cannot occupy the same substrate’, we must suppose that we are dealing with one body at the outset and that Theon is a part of Dion6.
- Second, the justification for Dion’s7 survival that Sedley supplies on behalf of Chrysippus seems right. The amputee who is grieving over his severed foot must be Dion8 since ‘Theon cannot have lost a foot that was never part of him in the first place’.
- Here is a very preliminary paraphrase of how Chrysippus’ argument appears to run that incorporates these points.
- At the outset we have one living, anatomically complete human being named Dion9, a region of whose body has been named Theon — the whole body except one of its feet.
- The foot just mentioned is then amputated, with the result that either Dion10 or Theon must perish because, as Chrysippus tells us (and as Philo apparently agrees), ‘two peculiarly qualified individuals cannot occupy the same substrate’.
- A dispute arises about who should perish.
- Chrysippus claims that Dion11 should survive and Theon should perish, since it cannot be Theon who is grieving over his severed foot.
- But Philo claims, on behalf of the Academics, that Theon must survive and Dion12 perish, ‘for how can it be that Theon, who has had no part chopped off, has been snatched away, while Dion13, whose foot has been amputated, has not perished?’
- I will argue in the sequel that the result favoured by Philo is congenial to what the Growing Argument would predict — that Theon should survive and Dion14 should perish — while the result favoured by Chrysippus is not. This, I believe, supports Sedley’s claim that Chrysippus’ puzzle is a reductio ad absurdum of the Growing Argument.
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