It is probably not surprising that the sad case of Alfie Evans — the 23-month-old boy who died in Britain last weekend after he was taken off life support over his parents’ objections — quickly devolved into mudslinging about the healthcare systems of Britain and the United States.

Ted Cruz, the Republican senator from Texas, Tweeted: “Systems of socialised medicine like the National Health Service vest the state with power over human lives, transforming citizens into subjects.”

Matthew Scott, a British barrister, retorted: “Had the Evans family been living in America, it is unlikely that Alfie would even have survived as long as he had, unless of course they had had the money or the insurance to pay for the paediatric intensive care that has kept him alive for months.”

American hospitals, of course, do not routinely shove indigent babies out of the NICU.

As for Cruz, the Evans case had little to do with NHS policy, or budgets.

Doctors overrule parents in the United States, too; for example, courts have allowed doctors to give children blood transfusions against the wishes of parents who are Jehovah’s Witnesses.

Of course, there are differences, as the Alfie Evans case and the similar Charlie Gard case suggest, in the degree of deference the two nations offer families.

And what happened in those cases does illustrate an acute danger — just not the dangers of national healthcare.

It is the danger of letting the centuries-long progress of liberal individualism go too far in breaking open the family and assigning its functions to the state.

That it has done so is beyond dispute.

Few of us in the modern West expect that our families will dictate our marriage choices, provide us with jobs and set us up with somewhere to live — an ordinary pattern for our ancestors and still common in much of the world. This has necessarily entailed some growth of the state to pick up some family functions, since the elderly, the ill and women with small children are often not viable economic units by themselves.

That this is generally a good thing is more arguable, but like most of us, I am happy to argue it.

Societies that depend too heavily on kinship ties risk falling into what political scientist Ed Banfield called “amoral familism”, in which the good of the family becomes the only end anyone recognises.

This is oppressive for individuals, and disastrous for the larger community, because mistrust and nepotism stifle economic activity and make it impossible for neighbours to work together for the common good.

Liberalism’s triumph means fewer people than ever live in those conditions. And yet triumphing armies often have difficulty finding the natural stopping point of their expansion.

It was startling to watch so many people ask, essentially, why we should prefer the opinion of the woman who gave birth to Alfie, over that of disinterested experts, as to what was in the best interest of the child.

But the people asking this make a fundamental logical error: They assume the experts know the answers to questions such as “What does ‘best’ mean?” and “What is the subjective experience of a child with Alfie Evans’s condition?”

It would be immensely comforting to think that experts do know the answers to these things, or at least could. But on the most fundamental questions of life and death, they grope just as blindly as the rest of us.

Which is why we should err on the side of the parents, particularly when we are not talking about life-saving treatments but about (or so the doctors insisted) modes of death.

The parents love the child best; they have, as author and philosopher Nassim Taleb says, “skin in the game”.

So even if they don’t have better answers to those metaphysical questions, they will care the most about getting it right.

Too, the fact that they care so much means the fate of the child is also the fate of his parents.

The death of a child is the worst thing that can happen to a human being, and yet, having that child killed in front of you is, incomprehensibly, even worse.

The state shouldn’t put anyone through that without very strong proof the parents are making a grave error that will actively hurt the child.

After all, the irrational, overpowering love of parent for child is the only reason most of us are alive, despite having spent the first years of our life vomiting, soiling ourselves and destroying everything we could reach.

If that love can see us to a healthy adulthood, it can probably see us to a decent death.

Disinterested management by experts will never substitute entirely for the family tie, because it seems to be wired into us at a deep level.

Studies show that institutionalised children don’t thrive. And neither can an institutionalised society with no space for the primal human bonds that sustain us.

Liberalism has won most of the battles it set for itself centuries ago. Now it needs to win the peace — by learning to recognise its limits.

•Megan McArdle is aWashington Post columnist and the author of The Up Side of Down: Why Failing Well Is the Key to Success