The primary objective of this paper is to improve the defense of the thesis that
(1) bodily continuity is the primary criterion of personal identity.
This is to be done by establishing (in Parts Ill and IV) that there is a unique sense in which
(2) bodily continuity is a necessary condition of personal identity.
A secondary objective of the paper is to illustrate (in Part I) the way in which the value and validity of (2) has been obscured in recent defenses and criticisms of (1), which inappropriately interpret it in terms of the claim that
(3) bodily continuity is a sufficient condition of personal identity.
Since the truth of (3) will be denied, the defense of (1) will also involve arguing (in Part II) that the traditional alternative to the bodily criterion, namely the criterion of memory and psychological characteristics, not only is not a necessary condition of personal identity but also is not a sufficient condition.