Two objections have been made to the argument that parents have responsibility for a child's state of peril:
By their nature, unborn children commit aggression against their mothers, so parents cannot be said to put children in peril by creating them.
Creating a child means giving the child a great benefit: life. Since life is a benefit, creating a child cannot be classified as putting them in peril.
The Argument That Unborn Children Initiate Aggression Against Their Mothers
This argument was advanced by Williamson Evers, who was influenced by Judith Jarvis Thomson. Evers in turn influenced Rothbard (Rothbard characterised unborn children as "coercive parasites" following this argument). Evers' line of argument is:
An unborn child "attaches itself" to the mother, "burrows into the wall of the womb" and "expands like Alice-in-Wonderland in the rabbit's house".
These actions constitute an "attack" by the unborn child on the mother and are "aggressive" in character (i.e an act of initiatory aggression).
Since the mother has been aggressed against, she has not put the unborn child in a state of peril by creating it.
Therefore parents in general do not put their children in peril by creating them.
There are things to contest in every premise of this argument, and even if you accept the premises, the conclusions do not follow. Using odd or aggressive words to describe various facts of pregnancy does not prove children are aggressors against their mothers. It is simply a fact of nature that babies embed in the womb and grow. This is not an act of aggression, it is a natural consequence of getting pregnant. The mother's own body plays the decisive role in facilitating, regulating, and nurturing the entire process.
Furthermore, there is no sense in which describing the steps of pregnancy using weird language challenges the core thesis regarding peril (that creating a child entails creating a situation of helplessness, and therefore responsibility). Evers' does not refute this.
Yet further, given his argument is all based around describing pregnancy, Evers also
A) ignores fathers completely, as if they have nothing to do with any questions of responsibility; and
B) fails to show how any of this relates to children once they are born (he merely asserts that the same conclusions from the pregnancy example somehow apply).
The Argument That Giving Life Is An Incomparable Benefit And Therefore Parents Are Not Obligated Further
This argument has the following form:
When parents create children, they are giving them the gift of life.
Life is a benefit of incomparable worth.
Since the parents have given something of incomparable worth by creating the child, it would be an injustice if on top of that they were obliged to provide other things.
I agree that life is a gift of incomparable worth. However, gifts do not nullify other obligations. The two are separate. This is especially the case since the obligation in this case is to relieve a state of peril. If I take you up in an aircraft, give you a million dollars in cash, and then parachute out of the plane leaving you unable to fly, I cannot legitimately argue "I gave you an enormous gift, therefore I don't have obligations to you!".
Evers makes this gift-of-life argument using an analogy. He argues that it would be unjust for someone who saves a child from a car crash (in which both parents have been killed) to then be lumbered with responsibility for the child.
There is something fundamentally different about this analogy. When parents create a child, they change the state of the universe from one in which there was no child in peril to one in which a rights-bearing child is in peril (the fact that the child did not exist beforehand is irrelevant to this argument). In contrast, the rescuer in Evers' example did not create the peril. He merely alleviates some of the immediate peril that a child was already in.
Arguably, whilst the rescuer still has the baby in his hands, he does indeed have a responsibility for it. He cannot simply abandon the baby directly after saving it from the accident. Although the rescuer was not obliged to save the child initially, once he did so it would seem to follow that he has to keep looking after that person until
A) he finds someone else who can take over the responsibility; or
B) the child is no longer helpless.
However, it does not follow that the rescuer would be the one responsible to raise the child to adulthood. In real life, there are many cultural practices to address what would happen in cases where both parents die, such as written wills that state who should have custody, or the practice of assigning godparents.
This kind of tragic accident is a foreseeable risk, so one of the positive obligations that parents have is to make arrangements for their childrens’ care in the event that both parents die before the children reach adulthood.