Fission and the Facts
Johnston (Mark)
Source: Philosophical Perspectives 3: 369-97
Paper - Abstract

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Author’s Introduction

  1. How far is Common Sense, a thing only partly invented, only partly a useful fiction, committed to anything that is philosophically problematic? The answer one gives to that question must significantly determine one's conception of the point and scope of philosophy, one's view of how far philosophy legitimately can have revisionary aspirations, one's sense of how satisfying a description of our practices can be if that description indeed leaves everything as it is, if it aims only to dissolve or diffuse conflicts among the justifications we give for those practices, if, as a matter of principle, it never finds a place for the diagnosis of vitiating error.
  2. The Revisionist makes his task easier by attributing to Common Sense proto-philosophical theories about features of our ordinary practices, theories which may then be shown to be internally incoherent, inconsistent with other things we take for granted or simply too primitive to take seriously. Thus philosophical pictures sometimes seem to be foisted on Common Sense. Our ordinary understanding of the passage of time is sometimes supposed to embody the picture of reality growing at one end and perhaps diminishing at the other at the same unspecifiable rate. Our ordinary conception of free will is sometimes supposed to involve a picture of free will as a kind of causation1 itself uncaused and yet somehow properly associated with particular human beings, where human beings are themselves depicted as morasses of causal determination. Our ordinary notion of being guided by a rule that determines a potentially infinite series of applications is sometimes supposed to depend upon picturing ourselves as being under the mysterious influence of a Platonic something which actually incorporates and organizes the infinite series of cases.
  3. Only when we descend to the details can we see how far these attributions merely foist and how far they tease out the implicit commitments of Common Sense. Here I am concerned with the details of the Common Sense View, if there is such a view, of the facts of personal identity and difference. However, before we examine the metaphysical model of the facts of personal identity attributed to Common Sense by Revisionists and Non-Revisionists alike, and exhibit in detail what is mistaken in it, it is as well to notice that the Revisionist who goes by way of attributing a proto-philosophical theory or model to Common Sense faces a general dilemma. Consider some proto-philosophical theory which such a Revisionist associates with some concept in ordinary use. Does that theory guide the actual use of the concept, i.e. determine its application in ordinary cases, or not? If it does, then to the extent that the Revisionist maintains the theory is shot through with falsity, to that extent he becomes an Eliminativist, depriving us of anything to have had a false view about. If it does not, the Revisionist's claim about the falsity of the theory is a claim about a more or less uninteresting epiphenomenon of ordinary practice, a bit of amateurish philosophizing on the part of Common Sense. The false theory would then be a curiosity, since ordinary practice does not rely on it any more than an aeronautical engineer who happens to be a logicist about mathematics relies on his logicism in his mathematical calculations. The Revisionist thus inherits the onus of explaining in particular cases how he finds a stable middle ground between adopting Eliminativism and simply remarking upon a theoretical epiphenomenon2.
  4. In the particular case of personal identity the master of the Revisionist gambit is Derek Parfit3. He makes a case for the claim that we have a false view of our natures as persons, indeed that we think of ourselves as separately existing entities distinct from our brains and bodies, entities like Cartesian egos4. So far from seeing the separately existing entity view as a theoretical epiphenomenon, Parfit5 argues that if we accept that this view is false then we should alter our practice in a certain way. Presently we use the concept of personal identity to guide our future-oriented concerns so that we care in a special and non-derivative way about ourselves as opposed to people merely continuous with us in rich and manifold respects. According to Parfit6 we should abandon or at least significantly weaken this non-derivative concern for ourselves once we see that we are not separately existing entities7.
  5. In first setting out his Revisionist argument Parfit8 relied heavily on the case of fission, which is my central example here9. About it, I argue that even if Common Sense had a view of personal identity at odds with the right thing to say in the fission case, this view would be at most a theoretical epiphenomenon. It does not in general guide our use of the concept of personal identity in ordinary cases. At worst, this view would be an overgeneralization from consequences in ordinary cases of our independent employment of the concept. Fission is a case outside the ordinary and it is a case in which there are no determinate facts of personal identity. Although this latter claim may surprise, it occasions no deep revision.


Also in "Noonan (Harold), Ed. - Personal Identity (Readings)".

In-Page Footnotes

Footnote 2:
  • Clearly the worry here expressed applies to that fashionable eliminativism about the psychological attitudes which stems from regarding "folk psychology" as a term-defining theory which has the singular vice of being largely false.
  • A typical response is to accept the picture of folk psychology as a term-defining theory, not concede that it is largely false and conclude that there are legitimate restrictions of the theory – i.e. large enough sub parts of it – within which the constituent propositional attitude terms have extensions.
  • But then the clear implication is that there are legitimate restrictions of the theory within which the terms have no extensions. So it's hard to see how the theorist who takes this line will be able non-artificially to claim that it is determinately true that people have beliefs.
  • Better to take a different tack and examine the possibility that folk psychology is not a term-defining theory at all but a collection of rules of thumb which have accumulated as a result of a successful practice not itself guided by theory, viz. the practice of understanding each other as believers and desirers. We can regard ourselves as knowing how to do this without needing to assume we know a lot of propositional truth.
Footnote 3: See Footnote 7: See "Parfit (Derek) - Reasons and Persons", pp. 199-302.

Footnote 9: See "Parfit (Derek) - Personal Identity", section 1.

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