Each side spins the uncertainty its way. Opponents of EC say pharmacists are entitled to refuse to sell drugs "suspected" of causing abortions. Proponents demand a "presumption" that Plan B does no such thing. If you're troubled by the moral or factual ambiguities, each side offers the simplifying comfort of semantics. Proponents say EC can't abort a pregnancy, since "medical authorities" define pregnancy as beginning at implantation. Opponents reply that "embryologists" define pregnancy as beginning at fertilization. Everybody wants to give you an authoritative answer, when there isn't one.
If the two camps were to stop spinning and listen for a moment, they might learn something from each other. Proponents of EC, who talk so much about choice and information, might realize that their denials of any abortion risk from Plan B, through semantics or stretching of the evidence, deprive women of informed consent. The right to choose a pill that's probably birth control but possibly abortion includes the right to know that's what you're choosing.
Opponents of EC might realize that the risk of abortion depends on when the drug is taken. The odds that it will abort an embryo, rather than prevent an embryo's creation, are very low. The earlier you get the pill, the lower the odds are. And every successful EC intervention spares a woman the greater danger of ending up with a surgical abortion. Plan B should be available over the counter so it can be what its advocates hope for, not what its enemies fear.
A version of this article also appears in the Outlook section of the Sunday Washington Post.