The social recognition of personhood depends on (1) stages of historical development; and, within a given society at a given stage of historical development, (2) the contest of ideas backed by social forces in conflict. In many premodern societies, newborns were not given names unless and until they survived till their first birthdays; in many of them, newborns who looked ill were exposed to elements or purposefully neglected by their families and communities. Was it because premodern peoples were callous? No -- rather, they did not recognize the personhood of newborns because much fewer of them could be expected to survive than today, without the level of economic development, medical progress, etc. that we now enjoy. Today, most societies recognize the personhood of newborns, because most newborns, without fatal disabilities, can be expected to survive; but we are not moral betters than ancients because of the difference.
How you define personhood depends on your politics today, especially whether you think of women to be persons with rights equal to men. Looking at the development of life from eggs and sperms, fetuses (ranging from the first day of conception to the last day of pregnancy), to babies, there is no inherent quality in any of them that can make anyone say, "Yes, here is _the_ threshold that defines the beginning of personhood!" If one considered fetuses in separation from women who carry them, one might very well conclude that the respective positions of orthodox Catholics and others (no contraception + no abortion), evangelical Protestants (no extramarital sex, contraception only within marriage, + no abortion), liberals (sex and contraception with or without marriage + women's right to choose), and left-wingers (sex and contraception with or without marriage, women's right to choose, + public funding of health care including abortion and other gynecological services) are moral and philosophical equals, as far as the question of the threshold of personhood is concerned. If you conferred personhood on a fetus on the ground that it is a life form, you might as well confer it on eggs and sperms also; at least there is no argument against doing so on that ground. -- Yoshie
* Calendar of Events in Columbus: <http://www.osu.edu/students/sif/calendar.html> * Anti-War Activist Resources: <http://www.osu.edu/students/sif/activist.html> * Student International Forum: <http://www.osu.edu/students/sif/> * Committee for Justice in Palestine: <http://www.osu.edu/students/CJP/>