The problem for the author of this essay is that any premise for a morality of any kind is as immaterial as 'God the Creator' is for Catholicism (and other religions). Whatever notions the author has of right and wrong and good and bad are every bit as profoundly subjective--as personal--as believing in God the Creator is.

An approach to governing the governance of society is available that involves no beliefs (including a belief that material existence is 'all there is'). This ethic of justice is limited to actions of human beings in effecting choices that involve any other human being(s) in any way.

We human beings have no choice but to effect choices (choose among perceived alternatives and take action to bring that choice to fruition). That makes choosing integral to being human. That makes that circumstance a material starting point for an ethic of justice that wholly contained within material existence.

Outside that vast but limited 'domain of justice' people would still be governed by personal morality and beliefs would still inform participation in the (democratic) political process: the process of effecting choices for the community as a whole--which every community must do as surely as every individual must.

If curious: "Can't Get Any Simpler" is a "2 min read" here in Medium with links to more about that ethic: nothing I publish here in Medium is behind the paywall.