A Dilemma for Personal Identity

Some theories of personal identity allow persons
to lose their identities in processes of qualitative change,
i.e., to become a numerically different person by getting
new physical and/or psychological properties. I shall call
these theories strong. Weak theories, in contrast, do not
allow for such a loss of identity. In general, weak theories
put less restrictions on personal identity than strong ones. I
will argue that each type of theory faces a serious problem.