Personhood is the name for whatever attributes or qualities define the difference between a person and anything else (e.g. animals), such that the entity is subject to the usual mores and laws which apply to people.
The terms "person" and "personhood" are used in order to include the possibility of non-human intelligent life being included in the debate; in other words, the term does not presume that there is anything special about the species homo sapiens merely because it is the only example of sapient life with which we are familiar; the important qualities are whatever causes us to think of such an entity as "a person" and hence reasonably subject to the same rules which we apply to ourselves.
The problem gets slippery in two directions at this point, however:
- What, exactly, are the necessary qualities for defining "personhood"?
- What if a person is subtly different from "us", such that our laws should not be applied without alteration?
Mary Anne Warren's criteria
Mary Anne Warren (who may have coined or popularized the term "personhood" in this context) has argued that the following qualities characterize personhood:
- consciousness (of objects and events external and/or internal to the being), and in particular the capacity to feel pain
- reasoning (the developed capacity to solve new and relatively complex problems)
- self-motivated activity (activity which is relatively independent of either genetic or direct external control)
- the capacity to communicate, by whatever means, messages of an indefinite variety of types, that is, not just with an indefinite number of possible contents, but on indefinitely many possible topics
- the presence of self-concepts, and self-awareness, either individual or racial, or both
personhood begins at conception
Many pro-life advocates state that human life begins at conception, and that therefore abortion should be considered unacceptable from that moment, i.e. from the beginning of pregnancy; in other words, all abortion is unacceptable. It seems reasonable to presume that people who agree with this point of view would define personhood as beginning at conception.
Moral absolutists hold that "rules are rules" and are valid regardless of the individual's circumstances or constitution, and (further) that any entity which is incapable of adhering to those rules (e.g. a hypothetical alien species whose normal lifecycle involves killing its own kind) is therefore not a person.
mores and laws
It is almost universally accepted that it is wrong to kill a person who has done no wrong, although many consider it to be allowable under certain circumstances (e.g. civilian casualties in wartime; euthanasia). This rule plays a large part in the debates over abortion and euthanasia and is often emphasized by pro-life advocates.
The concept of personhood arises within the debate over abortion, where the question can be rephrased thusly: At what point does a fetus become a person? If we accept a definition of "person" which includes the idea that it is wrong to kill a person who has done no wrong, then it would certainly be wrong to kill a fetus if the fetus has attained personhood (since there cannot yet have been any opportunity for the fetus to do any wrong).
This argument, however, seems to be somewhat oversimplifying the situation. For example, thinking of the fetus as being like someone in a coma (unconscious and unable to communicate), is it permissible to withdraw life-support? How does the fact of the fetus's likely "recovery" from this condition (requiring many years of "training" to gain adult competency) balance against the uncertainty of the coma victim's recovery? (And of course some people are vehemently against euthanasia even in the case of a vegetative state.)