How do you morally justify the requirement that children should support themselves when they reach adulthood?

Question

At least in a Western context people widely agree upon the idea that you have to do something voluntarily to be responsible for it. If you sign a contract voluntarily you are bound by it but if someone forces you, at gunpoint, to sign it you are not bound by it. The law and moral generally agree on situations like that.

And it goes even further, most of the time you must have intention to do something to be morally responsible for the consequences of it. If you stumble on a train because it makes a sudden stop and falls on someone who is injured, you are, generally, excused and not convicted for abuse, assault or similar - and most people think this is reasonable.

With all this in mind, how do people justify that children when they turn 18 or something like that no longer can expect their parents to support them?

The parents voluntarily and intentionally (they intentionally had sex, if the child was unplanned it is still a well known fact that having sex can lead to "accidents" and they obviously didn't terminate the pregnancy so in the "normal case" the child "happened" intentionally and voluntarily) had a child. The consequences of that decision is a human being that will need food, clothing, shelter and so on for the rest of her life.

However, by the logic from the first two paragraphs, the child is not responsible for her situation and the consequences of it because she didn't do anything to end up needing all this stuff for the rest of her life.

In fact, we are more generous towards our pets than our children in this respect. We never expect dogs and cats to provide for themselves when they reach a certain age. Instead we realise that getting a cat or dog means that we have to support it with food and shelter for its whole life (yes you can put down an animal but generally doing that to a healthy animal is frowned upon and most people would feel immoral putting down an animal because we don't want it anymore).

Two final remarks:

1. You can't own a human, at least not unless it voluntarily sold itself.
2. Suicide is, IMO, not a reasonable answer. We are biologically programmed to survive (Eat poison and you will throw up. If you are so determined that you can hold your breath until you pass out your autonomic nervous system will save you as soon as you no longer can control your breathing with will power.). It would have been different if our biology were indifferent between life and death.

So how do you morally and ethically motivate that a child must take responsibility for her parents' decision just because she turns 18 (or something like that)? Why aren't parents obliged to support and provide for their child's basic needs for the child's whole life?

Answer 1

To answer your question through science, humans have evolved the capacity to have self control as other animals. In particular, we have the largest percentage of prefrontal cortex than any other species - which is the part of the brain that has the ability to control our innate impulses. Hence, we hold people accountable for their actions to the degree to which they have the capacity to have self control. Specifically, children do not have a fully developed prefrontal cortex yet until about the age of 25. However, for the purposes of recognition and indoctrination into society, it is generally recognized the age of 18 is sufficient enough to become an independent adult. At that point the parents have no moral obligation to support another adult regardless of whether or not that individual is biologically related.

Because responsibility is, at least partially, dictated by necessity, and because the necessity to continue providing has (sufficiently) been rendered void due to the capability of the child now being enough so they can take care of themselves, the parents' responsibility to support and provide for their child's basic needs for the child's whole life is also sufficiently voided/reduced. In other words, there is a difference between necessity to provide and a desire to provide, whereby the necessity is impacted by the (increasing) capabilities of a child to care for themselves.

I think it is noteworthy to mention that there is a difference between Western and Eastern countries such that the latter have more of an emphasis on family values such as caring for one's parents in their old age (and going insofar as having relatively larger families in each household). I believe this has been degrading though.

Following this, there are four ways the age of 18 and continued support can go. 1. The child desires to continue being supported but not the parents 2. The parents desire to continue supporting the child (and realistically using it as leverage to control the child's life) but the child does not, 3. Both the child and the parents desire for the child to continue being supported, and 4. neither the parents or the child desire for child to continue being supported. This does not account for how often these actually occur. However, at a static level along with how typically decisions such as these require all parties to agree for them to occur, 3/4 of the situations result in the child not being supported.

The reason "desire" is relevant is because of two reasons. One, biologically the general consensus is that humans are fundamentally driven by self interest (and although this is particular debate amongst philosophers and psychologists, that stance will be taken as a perspective through which to answer). Passing one's genes on is good, and is a form of self-interest so they too can pass on their genes on their own. However, this job is not complete until the child is capable of taking care of themselves. This goes into the second reason which is that the child typically does not want to continue being supported because having parents would actually be a hindrance on their life, and in contrast to their self interest. Whether it be the ego and self-righteousness to make their own way through the world, or to avoid annoyance and control on their life from parents leveraging support on them, or simply supporting their parents when the parents are unable to support the child.

As an example of this, there are a host of examples in the animal kingdom where parents and their children part ways at a sufficient age. Furthermore, although I touched upon it, I think the idea of autonomy and the philosophical literature surrounding it could be connected and used to answer your question.