What is "fairness". Fairness is a technical concept, not a moral one. It is distinct from justice. And because it is not a moral concept, it is not always moral to be fair.+
More specifically, being "fair" is being "proportionate". There are three interweaved types of being "proportionate" in the sense of fair: Equality (proportionality to unit); proportionality to action (desert); & proportionality to another specific metric (eg wealth or need).+
It's easy to see that it is not always moral to be fair. Three key cases of this are: family; property; promise. Family: I do not give my own kids Christmas presents but not those of other parents cos mine are more deserving or need them more. I do so cos they are mine.+
Property: I do not buy chocolate bars equally in every convenience store or buy them where I do cos that store is more deserving of my custom. I do so cos my money is mine to use as I will.+
Promise: If I promise to help my friend move house on Saturday, I don't then help him cos I'm rotating through all house-movers or cos he deserves my help more. I do so cos my promise binds me.+
So family, property & promises all morally trump or outrank fairness. But these 3 are the traditional building blocks of society. So any society will be & should be unfair. Without such unfairness, we have destroyed essential elements of family, property & promise.+
Thus we should not say "Life is unfair" as if that were regrettable but unavoidable. We should say: "Life is unfair because life ought to be unfair."
One interesting feature of fairness is that it serves as a residual. If we have no morally richer basis for acting/allocating, & do not then act fairly, we are guilty of being arbitrary.+
+That role of fairness as the moral residual means that as a society's confidence in morally richer or more complex principles declines, fairness becomes more significant. We worry more about fairness when we cease to believe in anything else.
A child worries about fairness because it hasn't learned yet that anything else matters. An adult regards fairness as the moral requirement when it ceases to believe anything else matters. Fairness is the morality of the nihilist.
