Morality is any system the human mind invents, that, through our faith in it, achieves emergence and stability (existence) and has a beneficial effect on society.
Not every invented system of human principles is moral. Only those systems that resonate enough with humans to induce believe and faith, and which benefit society through this belief. The act of faith itself, across a broad enough swath of society, gives the system moral existence.
We (in America) believe everyone is morally equal. We believe in individual liberty. You can't prove these concepts are true, but belief in them has a powerful organizing force in society.
We (in America) believe in the moral principle of "no man left behind" in battle. We take it on faith, even knowing that many soldiers could die when rescuing just one fallen man. With that faith, other soldiers know they will be rescued if captured, and so don't reveal secrets to the enemy, an enormous practical benefit.
Free Will is another such moral concept. While most scientists agree that we humans don't have Free Will, the belief itself has a positive benefit on society. It's the basis of the legal system and personal responsibility for your actions. Our faith in Free Will, not the truth behind it, gives it powerful moral authority.