Mark Johnson argues that moral deliberation is a form of problem-solving, in which possible courses of action are imagined and evaluated using all information we currently have available to us. It is not a matter of applying pre-existing moral axioms - either god-given or rationally derived à la Kant - but rather a creative exercise in inventing new solutions to new problems. He calls this approach ethical naturalism. Johnson relies heavily in John Dewey and argues against Immanuel Kant, whose ethics he considers to be actually very similar to the religious fundamentalist's idea of morals as given by a commanding god, but minus the god. He says that in the same way that Kant tried to de-theologize Judeo-Christian ethics, so Rawls tries to de-transcendentalize Kant, removing Kant's claims of absolute foundations in pure practical reason, while keeping most of the rest of Kant's moral vision. He defends Dewey's idea of the "qualitative unity of the situation", but I fail to see what that position actually does. It seems to me that this particular line of argument makes the theory more prone to relativism than it needs to be.
Basically, Johnson considers the quest for ethical certainty in a small set of moral axioms to be fundamentally mistaken. Moral problem-solving is an empirical inquiry. He maintains that this does not lead inevitably to relativism. Criticism of moral ideals is possible, and we are not prisoners of our inherited moral frameworks. Progress is possible. In my mind, his approach fits very well with the evolutionary wave of thinking that is currently under way in the science and philosophy of human nature. Although he does not refer to Karl Popper or Michael Tomasello, I think there are clear points of contact in the approach.
I can recommend this text. It is well written, clear and forceful. Its provokative ideas made me think about ethics in a new way.