If someone falls into a lake, bystanders have no enforceable obligation to save them. However, if you push someone into a lake, you have an enforceable obligation to save them because you are responsible for putting them in a state of peril.
When parents create a child, one consequence is that the child is in a state of temporary helplessness or peril. Therefore, the parents have an enforceable obligation to bring the child out of this state of helplessness. This means doing whatever it takes to raise them safely to independence, self-sufficiency, and adulthood. The parents have responsibility for the child in the same way that someone who pushes a person into a lake has a responsibility to rescue them. This is the basis of the Theory of Parental Responsibility.
A competing theory argues that creating a child does not entail placing someone in peril and therefore parents do not have enforceable obligations. In this view, parents are more like the bystanders who see someone fall into a lake. The child may be helpless (I.e. in peril- just as the person in a lake is in peril) but this view argues that the child's helplessness is not a source of responsibility for the parents. This alternative view is the Theory of Parenting as Charity.
Parental obligation does not arise through contract but rather as a result of the parents' actions being causally responsible for the peril that the child faces. Even if the parents did not intend to create a child (and even if they took the precaution of using contraceptives), creating a life was a foreseeable risk that they are responsible for. In legal terms, it is a strict liability tort.
It is a well established principle of law that one way of acquiring positive obligations is by placing someone in a state of peril. The theory of parental responsibility rests on this principle. In a future post, I will address some objections to this argument.