This paper considers the question whether a psychological approach to personal identity can be formulated within an endurantist, as opposed to four-dimensionalist, framework. Trenton Merricks has argued that this cannot be done. I argue to the contrary: a perfectly coherent endurantist version of the psychological approach can indeed be formulated.

The rich resources of the Four-Dimensional metaphysics have been brought to bear upon many traditional philosophical problems in recent years. Alas, the implications of Four-Dimensionalism for bioethics have gone largely unexplored. Hud Hudson is the rare exception. Relying upon a Four- Dimensional metaphysics of temporal parts and a belief in unrestricted composition, he argues that there is little reason to identify the perduring human embryonic animal and the perduring human person. He makes the intriguing claim that if abortion is wrong, (...) then it is not because the human animal within its mother’s womb is a person. This he rightly claims “is a very significant result” for “an overwhelming amount of the literature on abortion and infanticide (as well as much of the public debate on these topics) seems to turn on the question of whether or not the human fetus is a person.” [3, p. 153]. (shrink)

Consider a specific type of fission where psychological continuity takes a branching form, and one of the offshoots comes into being later than the other offshoot. Let us say that the earlier offshoot comes into being in the left branch at t, and the later offshoot comes into being in the right branch at t+1. With regard to the question how many persons are involved in this case, three answers are worth considering: (i) The original subject persists up to t; (...) a distinct person comes into being immediately after t and continues to exist in the left branch; and the third person comes into being in the right branch at t+1. (ii) The original subject persists up to the moment immediately before t+1; a distinct person comes into being at t+1 and continues to exist in the left branch; and the third person comes into being in the right branch at t+1. (iii) The original subject continues to exist in the left branch; a distinct person comes into being in the right branch at t+1. For those who hold that personal identity consists in psychological continuity of some sort, the aforementioned three options exhaust the sensible ways of understanding how one persists in delayed fission. However, I argue that complications arise for each answer. Hence, delayed fission poses a challenge for the psychological approach to personal identity. (shrink)