Derek Parfit – the psychological view of personal identity
2009: Advance directives and personhood
Parfit takes the view that personal identity is constituted over time by varying degrees of continuity between former and later selves in terms of a wide range of psychological and physical features. The psychological aspect of personal identity is constituted by the degrees of similarity between two temporally separate selves with regard to a person’s personality, belief structure and desires, which may in certain cases (such as advanced dementia) depending on the degree of similarity and continuity, move from being intra-personal to being inter-personal.
In certain cases of advanced dementia, it could be argued that psychological continuity is so deeply disturbed that someone has become another person. In such cases, an advance directive should have no more moral force in connection to the course of action to be currently taken than it would have had, had it been written by a stranger, friend or relative. A person with advanced dementia may have totally different interests to those they had as a person without dementia. It would follow from Parfit’s theory, that there are no moral grounds to respect advance directives in such severe cases.
However, according to Parfit, continuity between the former and current self is a matter of degree in that there may be a strong, weak or no relationship at all between the different selves. With reference to advance directives for research involving people with dementia, Berghmans (1998) states that according to the psychological view of personal identity, the moral authority of an advance directive would be less diminished in the earlier stage of dementia than in the later and more severe stages because memory loss and other psychological changes would not be as marked as in the later stages. This observation could presumably be applied to advance directives involving wishes other than those linked to participation in research.
Last Updated: Friday 09 October 2009