In what might still be the most famous moral-philosophical defense of abortion, Judith Jarvis Thomson admitted that “we shall probably have to agree that the fetus has already become a human person well before birth.” “By the tenth week,” Thomson observed, the fetus “already has a face, arms and legs, fingers, and toes; it has internal organs, and brain activity is detectable.” Though she denied that “the fetus is a person from the moment of conception,” she granted that proposition for the sake of arguing for a broad right to abortion.
“Opponents of abortion commonly spend most of their time establishing that the fetus is a person, and hardly any time explaining the step from there to the impermissibility of abortion,” she observed, but “it is by no means enough to show that the fetus is a person, and to remind us that all persons have a right to life,” for “we need to be shown also that killing the fetus violates its right to life, i.e., that abortion is unjust killing” (emphasis added).
Thomson tactically conceded fetal personhood, hoping to show that the right to abortion does not turn on the question of a fetal right to life. To put it differently, Thomson understood that the central question of the abortion debate concerned the extent to which abortion could be justified if it is the killing of one person by another. If it could be justified at all, the justification would have to appeal to principles that can be applied consistently across the board.
Read more at the Public Discourse.