“Despite the reticence of most scientists on the subject of good and evil, the scientific study of morality and human happiness is well underway. This research is bound to bring science into conflict with religious orthodoxy and popular opinion—just as our growing understanding of evolution has—because the divide between facts and values is illusory in at least three senses: (1) whatever can be known about maximizing the well-being of conscious creatures—which is, I will argue, the only thing we can reasonably value—must at some point translate into facts about brains and their interaction with the world at large; (2) the very idea of “objective” knowledge (i.e., knowledge acquired through honest observation and reasoning) has values built into it, as every effort we make to discuss facts depends upon principles that we must first value (e.g., logical consistency, reliance on evidence, parsimony, etc.); (3) beliefs about facts and beliefs about values seem to arise from similar processes at the level of the brain: it appears that we have a common system for judging truth and falsity in both domains. I will discuss each of these points in greater detail below. Both in terms of what there is to know about the world and the brain mechanisms that allow us to know it, we will see that a clear boundary between facts and values simply does not exist. Many readers might wonder how can we base our values on something as difficult to define as “well-being”?”