So religion--faith--is a form of immaterial, personal truth after all. So is any secular belief, such a belief in the moral equality of all people or a belief in the existence of 'Natural Rights' or 'Human Rights' with no reference to anything beyond material existence.

Meanwhile, we live together in geopolitical groups (nations, states/provinces, cities/towns, etc.). Such groups require governance. All forms of governance exhibit some organizing principle, even if it is only 'rule by the most ruthless'. Just governance requires some 'higher' principle, one that constrains everyone, to include, as former President (W.) Bush would say, the “deciders," those in the offices of government--and for that matter would determine the structure and sanctioned functioning of the political process (of which the offices of government are its functional core) and the economy.

To apply to all, that principle must be universal. Any belief could be universal. There is no belief that is universal, that all people hold in common. The only commonality we humans share is our experience of material existence.

Even there, differences do arise. Yet, there are some experiences of material existence that all people do share in common. One is the fact of human existence that we have no choice but to effect choices, i.e., choose among perceived alternatives and take action to bring that choice to fruition.

That makes choosing integral to being human. So, we have there the starting point for a truly universal ethic to govern the governance of any community, however large/complex or simple/small it might be.

if ready for more: "Alright, Already" (here in Medium, but not behind the paywall)