On Parfit’s Psychological Criterion of personal identity, I persist as some future subject if we can trace a chain of overlapping mental state connections from me to that future subject. When two subjects are connected in this way, we can say that they are psychologically continuous. Parfit offers up three different versions of the Psychological Criterion in Reasons and Persons, and what he calls the Narrow, Wide, and Widest views are distinguished from one another by what is acceptable as the cause of continuity on each. However, there appear to be problems with all three versions. On the one hand, the Wide and Widest views are so generous with how ‘cause’ is defined that they no longer deal with the persistence sense of personal identity at all. On the other hand, the Narrow View has a more appropriate definition of ‘cause’, but treats all types of mental state as equal contributors to continuity. This also becomes a problem when we consider cases where overall continuity obtains but certain moral features have been altered—as in some instances of traumatic brain injury where the original subject intuitively may not seem to persist through the injury. To this end, in this paper I examine Parfit’s Psychological Criterion and argue that none of its three versions succeed as persistence accounts. Nonetheless, I do think that the Narrow View in particular can be appropriately modified to harmonize with these moral problem cases by the addition of a new relation that is necessary but not sufficient for persistence: moral continuity.
Although Derek Parfit first tested the waters with the paper “Personal Identity” (1971), it was of course the carefully curated refinement of those views in Part Three of Reasons and Persons (1984) that proved to be a watershed moment for the philosophy of personal identity. His talk of Teletransportation to Mars, brain transplants, and divided consciousness was not only enthralling, but shaped the nature of the personal identity debate for the next several decades.
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