In a conversation I had recently with a friend who is a Christian, he shared with me that he’s raising his children to respect their parents because that is the commandment of their God.
“What if they grow up and stop believing in that God?” I asked.
This demonstrates a terrible flaw in externalizing morality. If the fictional nature of the entity enforcing a moral code is understood, the former believer is left in a moral vacuum–some form of nihilism typically follows.
A personal morality, generated by reason from first principles, doesn’t share this flaw. Why is it, then, that parents don’t teach children to use reason and evidence to build their own moral code? Part of the reason is that “respect your parents” isn’t included in such a code.
If you want to guarantee a lifetime of respect from your children, you need to act in such a way that their natural, inborn tendency will be to respect you. A good way to risk that respect is by making it a part of an arbitrary moral code. A great way to lose that respect is to verbally or physically punish a child in the name of said arbitrary moral code.