Singer and Dawson point out that two arguments against abortion, that the embryo is entitled to protection because from fertilization it is (1) a human being or (2) a potential human being, are also used by opponents of embryo experimentation. They focus on the second argument, evaluating the notion of potentiality as it applies to gametes, to the unimplanted embryo, to the implanted developing embryo, and to the embryo created by in vitro fertilization (IVF). They argue that there is a (...) crucial distinction between natural reproduction, in which all that is needed for the embryo to have a prospect of reaching its potential is for those involved to refrain from stopping it, and IVF, in which the embryo cannot develop into a person without a deliberate human act. Reproductive techniques necessitate our rethinking of established views about potentiality, and how it should be applied to the embryo in a laboratory. (KIE abstract). (shrink)