How can we establish the authority of a decent public morality in a plural society?

Comte identified morality with altruism
To answer this question, some post-Christian secularists turn to evolutionary biology and game theory. They identify morality with altruism and then seek to conjure altruism out of genetic selfishness. In his recent article in Standpoint Magazine, Professor Nigel Biggar outlines the problems associated with this approach and argues how the Christian moral vision tells a better story.
Thomas Aquinas and Joseph Butler tell a better story than Hobbes. They can account for the various data of the springs of human motivation without having to force them onto a procrustean bed of materialism. What is more, their story gladly embraces the notions of human dignity and rights that most materialists strive to retain in schizophrenic defiance of all their premises. This is why Jürgen Habermas, the eminent (and atheist) German public intellectual, was moved to confess to Le Monde some years ago that religious traditions — not least the Christian one — “have the distinction of a superior capacity for articulating our [liberal, humanist] moral sensibility”.
