For example, anti-abortion groups sometimes cite alleged medical and psychological risks of abortion, such as the existence of post-abortion syndrome or the abortion–breast cancer hypothesis.
Consequentialist arguments on both sides tend to be vigorously disputed, although they are not widely discussed in the philosophical literature.
Finally, there are some post-natal humans who are unable to feel pain due to genetic disorders, and thus do not satisfy all of Warren's criteria.
Warren agrees that infants are non-persons and so killing them is not strictly murder but denies that infanticide is generally permissible.
This clarification has critics of its own, as beef cattle, chickens, or any other livestock raised for meat—or even some plants—have supporters who would pay to keep them alive.
Warren grants that her argument entails as a logical consequence that infanticide would be morally acceptable under some circumstances, such as those of a desert island.
Philosopher Peter Singer similarly concludes that infanticide, particularly of severely disabled infants, is justifiable under certain conditions.
[17] Jeff McMahan grants that, under very limited circumstances, it may be permissible to kill one infant to save the lives of several others.
[18] Opponents may see these concessions as a reductio ad absurdum of these writers' views, while supporters may see them merely as examples of unpleasant acts being justified in unusual cases.
[21] Some defenders of Warren-style arguments grant that these problems have not yet been fully solved;[22] at the same time, they reply that the natural capacities view fares no better.
Some critics reject the natural capacities view on the basis that it takes mere species membership or genetic potential as a basis for respect (in essence a charge of speciesism),[24] or because it entails that anencephalic infants and the irreversibly comatose have a full right to life.
Respondents to this criticism argue that the noted human cases in fact would not be classified as persons, as they do not have a natural capacity to develop any psychological features.
[26][27][28] A seminal essay by Don Marquis argues that abortion is wrong because it deprives the embryo of a valuable future.
Similarly, killing a child or adult may be permissible in exceptional circumstances such as self-defense or perhaps capital punishment, although these are irrelevant to standard abortions.
One response is that neither the sperm, nor the egg, nor any particular sperm-egg combination, will ever itself live out a valuable future, and what will later have valuable experiences, activities, projects, and enjoyments is a new entity, a new organism, that will come into existence at or near conception, and it is this entity, not the sperm or egg or any sperm-egg combination, that has a future like human beings.
[35] Marquis's argument requires that what will later have valuable experiences and activities is the same entity, the same biological organism, as the embryo.
On certain theories of personal identity (generally motivated by thought experiments involving brain or cerebrum transplants), each human beings is not a biological organism but rather an embodied mind or a person (in John Locke's sense) that comes into existence when the brain gives rise to certain developed psychological capacities.
The defender of Marquis-style arguments may give the counterexample of the suicidal teenager who takes no interest in their future but killing whom is nonetheless wrong and murder.
A defense of this objection is likely to rest, as with certain views of personal identity, on thought experiments involving brain or cerebrum swaps, and this may render it implausible to some readers.
Her central argument involves a thought experiment where an individual, named Bob, wakes up in bed next to a famous violinist.
In most cases of abortion, the pregnant woman was not raped but had intercourse voluntarily, and thus has either tacitly consented to allowing the embryo to use her body (the tacit consent objection),[50] or else has a duty to sustain the embryo because the woman herself caused it to stand in need of her body (the responsibility objection).
[55] Alternative scenarios have been put forth as more accurate and realistic representations of the moral issues present in abortion.
This view is represented by some forms of humanism and by moral philosopher Rosalind Hursthouse in her widely anthologized article "Virtue Theory and Abortion".