- On one familiar and very broad view of personal identity1, the continued existence of a person over time admits of analysis in terms of relations of non-branching physical and/or psychological continuity2.1 (One version of this view is the Psychological Criterion, according to which A at t1 is identical to B at t2 iff A and B stand to each other in the relation of non-branching psychological continuity3.)
- The need for a non-branching or no-competitors clause is occasioned by the most plausible description of the division or fission of persons, a situation in which one individual stands to each of two later individuals in qualitatively identical relations of physical and psycho logical continuity.
- The inclusion of such a clause is necessary in order to avoid the consequence that the earlier person is identical to both resulting persons. The inclusion of a non-branching component in theories of personal identity over time has been thought to incur the charge of absurdity. The charge can be pressed as follows: any best-candidate theory of personal identity, which incorporates a non-branching component, violates a necessary constraint which governs our concept of strict numerical identity and - absurdly - implies, in a sense to be characterised, that the identity of a person over time can be extrinsically determined. Consequently, any best-candidate theory of personal identity over time is untenable.
- If so, it follows that we must redescribe the transtemporal identities which hold in a case of division, e.g., along the lines suggested by Lewis, Perry and Noonan4 (according to which the distinct post-division persons both occupy the single pre-division body), or else5 give up entirely the attempt to analyse the identity of a person over time in terms of physical and/or psychological continuity6 (and embrace instead, e.g., Cartesian dualism). However, my ultimate aim in this paper is to show how commitment to the extrinsicness of identity on the part of best-candidate theorists can be accepted without absurdity.
From "Noonan (Harold), Ed. - Personal Identity (Readings)".
- See, e.g., Parfit's statement of the Physical and Psychological Criteria in Reasons and Persons, Oxford University Press, 1984, p. 204 and p. 207. See also S. Shoemaker, 'Personal Identity: A Materialist's Account' in S. Shoemaker & R. Swinburne, Personal Identity, Oxford, Basil Blackwell, 1984.
- D. Lewis, 'Survival and Identity' in A. 0. Rorty (ed.), The Identities of Persons, Los Angeles, University of California Press, 1976; J. Perry, 'Can the Self Divide?', Journal of Philosophy, 1972; H. Noonan, 'The Closest Continuer Theory of Identity', Inquiry 28, 1985.
- This disjunction follows on the assumption, defended below, that division is a genuine metaphysical possibility for persons.
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