But I thought of another reason why I believe morality exists. Because true morality is hard. I'm not talking about sparing someone's feelings when they ask you if they've gained weight or refraining from committing a crime. These are the easy things; social and legal forces are very overreaching and keep us in line. No, I'm talking about the hard choices. Putting yourself in physical danger because it's the right thing to do, living ascetically to escape the corruption of material wealth, quitting your job because of an ethical situation that you have little part in (like say... selling advertisements for cigarettes or dangerous pharmaceuticals that you yourself would never use.) Acts of serious courage and sacrifice are things you don't see every day; I myself confess that I've never made any risk or sacrifice great enough to stop questioning my own virtue.
What does this have to do with anything? Isn't that arbitrary? Well, no. Saying that something is hard is a way of saying that it means something. Cowardice is a dime a dozen. If I make a choice between an act of courage and an act of cowardice, it's not like both are decisions with equal weight. One is easy and common, the other rare and difficult; so it must mean more—just like it's more meaningful for me to write these words on paper than to just punch random unintelligible keys; or to solve a difficult math problem instead of make an unsubstantiated conjecture about something based on nothing.
In other words, truly moral actions will have greater information content. They prove something, even if that something may be "arbitrary", just like math; a subject in which we still value proofs (for good reason.) Just as a game means nothing if there are no rules (with the exception of Calvinball), an action means nothing without difficulty. Cowardice, greed and hatred, on the other hand, never prove anything. There's no test, no rules and no meaning.