The relationship between ethics and science has been discussed within the framework of continuity versus discontinuity theories, each of which can take several forms. Continuity theorists claim that ethics is a science or at least that it has deep similarities with the modus operandi of science. Discontinuity theorists reject such equivalency, while at the same time many of them claim that ethics does deal with objective truths and universalizable statements, just not in the same sense as science does. I propose (...) here a third view of quasi-continuity (or, equivalently, quasi-discontinuity) that integrates ethics and science as equal partners toward the uncovering of new knowledge. In this third way, a program envisioned by William James but made practicable only by contemporary scientific advancement, science can and must inform ethics at a deep level, and ethical theory— while going beyond science—cannot do without it. In particular, I identify four areas of ethics-science collaboration: neurobiological research into the basis of moral judgment, comparative anthropol- ogy, comparative evolutionary biology of primates, and game-theo- retical modeling. I provide examples within each of these fields to show how they link to ethical theories (including prescriptive work) and questions. The essay concludes with a brief discussion of the light that a scientifically informed ethics can shed on some classical problems in moral theory, such as the relationships between rational- ity and selfishness, egoism and altruism, as well as the concept of social contract. A joint research program involving both philosophers and scientists is called for if we wish to move ethical theory into the twenty-first century. (shrink)