Footnotes

• ↵i Note that it is active potential—the power of an entity to act, while remaining the same entity⁴⁵⁶—which is in question here. The passive potential of a cell to be used to produce a different kind of entity is a separate phenomenon. True, embryonic cells are particularly plastic in terms of their ability to produce (or help produce) new organisms when isolated from and/or combined with other cells. We should, however, remember that adult cells can also be used to produce new living organisms, either by fertilisation or by cloning. Indeed, human adults, and even their gametes, have an active, not a mere passive potential to reproduce sexually—although they will forfeit their identity in the process in the case of gametes. Adult cells, like embryonic cells, can also be incorporated into existing organisms, as in stem cell research. The plasticity of a being’s parts—that is, their ability to be put to new uses—does not change what those parts now constitute, or any moral claims that being may have.

• ↵ii To say that the nuclear genes are necessary for the embryo’s existence is not, however, to say they are sufficient, or that the human organism is reducible to its genes.

• Competing interests: None.