  Derek Parfit was among the first contemporary theorists to explore  the relation between identity and ethics explicitly, first in his  seminal early 1970s articles, “Personal Identity” and  especially “Later Selves and Moral Principles,” and then  in his restatement and development of the view in Part III of his  1984 book Reasons and Persons (from which the present  exposition is taken). Parfit's is, in many respects, a Lockean  account of personal identity, although there are significant  departures. He is a “reductionist,” according to which  the facts about persons and personal identity consist in more  particular facts about brains, bodies, and series of interrelated  mental and physical events (Parfit 1984, 210–211). The denial of  reductionism is called “nonreductionism,” according to  which the facts about persons and personal identity consist in some  further fact, typically a fact about Cartesian egos or souls.