For most of human history it used to be standard practice for parents to insist that their children not only live by principles the parents have found to be sound but also to adopt all sorts of practices of dress, play, work, taste and so forth that they approve of. Father was a barber so son, too, had to be; mother raised four children, so daughter, too, must bear the same number. Parents liked living by the sea, so the kids too must follow suite. Indeed, if a child had another idea, all hell tended to break loose. And those around the family who didn't conform were deemed to be weird or inferior or just plain different in that sort of way that 's quite intolerant of such a thing.

In some cases this was a useful practice but more often it was a matter of habit, nothing much else. And since there are some matters concerning which one size does indeed fit all – such as certain ways of dealing with other people, certain ways to governing one's life, and certain ways of setting up a human community, e.g., honestly, prudently, and justly, respectively – the idea has always been somewhat palatable. In nutrition, medicine, engineering, farming and so on some ways clearly are better than others no matter who is doing it.

Yet, it dawned on many folks in time that not everyone should act the same way, work on the same tasks, or wear the same kind of clothes or haircut, if for no other reason than because people faced significantly different situations in their lives. And, most evidently, they were themselves rather different, even unique. So a tall son would not fit well in the kind of clothes worn by a diminutive father. Hat and shoe and glove sizes aren't the same for all. And once these and other differences got noticed and taken more and more seriously – as individuals were being paid more attention to as individuals – others managed to surface. In time the notion emerged that individuality is itself something important in our lives, that one isn't replaceable by someone else except in special circumstances – say if one weighs the same as someone else where weight is what counts for most. So while in team sports substitutions are routine, they cannot easily be replicated elsewhere, such as in romantic love or friendship. Once it is clear that it isn't just what one is but who one is that matters a lot, the one size fits all mentality comes under serious challenge.

But not everyone likes it and bad habits die hard. Even in markets it is very tempting to treat all potential customers as if the same goods and services were proper for them all. Thus we have mass marketing of stuff that really can only benefit some people – a certain type of exercise, a back ache cure, or a headache remedy. The more this is understood, the more the notion starts to make sense that one person's way of life could well be perfectly well suited for that person without this being an offense to others for whom it is not suitable.

Yet the idea persists that everyone ought to worship alike or admire the same artists or fashion designer's work. Here the temptation isn't just a mistake but also a desperate hope since if one size does fit all, those who make that size will be able to cash in on this big time. Everyone should love Pepsi, Coca Cola, a Chevy, a Volkswagen, or a Bentley or take a vow of poverty or love the outdoors. Of course in some cases qualitative considerations do recommend conforming to what others prefer and do but more often what is best for Jerry could well not be best for Harry or, especially, for Sue.

Figuring out when one size does versus does not fit all – or most – isn't that easy but it is usually worth the trouble, at least if it matters how happy one will be with what one pursues, has, or does in one's life. For wearing the hat that doesn't fit one is clearly uncomfortable, to say the least; and pursuing a career that will not be fulfilling can be a major hindrance to living happily.