John Jefferson Davis, Human Embryos, "Twinning," and Public Policy.

John Jefferson Davis, Human Embryos, "Twinning," and Public Policy, ETHICS & MED., Sum. 2004, at 35.

In his influential book, When Did I Begin?, Norman Ford argued for a fundamental distinction between "potential" human individuality and "actual" human individuality. According to Ford, while genetic individuality begins at fertilization, "ontological" or fully actual human individuality is not established until some time after the fourteenth day following fertilization, since prior to that time, the nascent human entity is capable of splitting or "twinning," leading to the birth of identical (monozygotic) twins. Such arguments from the possibility of human twinning have been appealed to by others as a basis for public policies allowing experimentation on human embryos prior to day fourteen, it being presumed that no true, distinct human being yet exists.

This article argues that Ford's understanding of human individuality...