KIE: Lockwood's essay is one of three in this issue of Bioethics on potentiality and its applicability to research with human embryos. (See also Richard M. Hare's "When does potentiality count? A comment on Lockwood," and Stephen Buckle's "Arguing from potential.") The author critiques the reasoning behind some of the proposals for regulating such research, particularly the recommendations of Britain's Warnock Committee and Enoch Powell's legislative response, the Unborn Children (Protection) Bill. Lockwood attempts to formulate a logically defensible and morally plausible position on potentiality, arguing that it is potential plus identity, which depends on brain development, which generates moral claims. He concludes that, while there may be practical reasons for banning embryo research after the nervous system begins to develop, it may not be morally wrong to experiment with miscarried fetuses whose brain is developing, but who are nonviable.