In the preceding chapters, we considered difficult questions concerning the ethical permissibility or desirability of various ways of intervening into the minds of human beings. In examining these questions, we took for granted the reliability of the ethical theories, principles and judgments to which we appealed. But some thinkers have argued that the sciences of the mind are gradually revealing that we cannot continue to do so. Neuroscience and social psychology, these thinkers claim, show that our ethical judgments are often, perhaps even always, unjustified or irrational. These sciences are stripping away the layers of illusion and falsehood with which ethics has always clothed itself. What lies beneath these illusions? Here thinkers diverge. Some argue for a revisionist view, according to which the lesson of the sciences of the mind is that all moral theories but one are irrational; on this revisionist view, the sciences of the mind provide decisive support for one particular ethical theory. Some argue for an eliminativist view, according to which the sciences of the mind show that all moral theories and judgments are unjustified. In this chapter, we shall assess these twin challenges.

How is this deflation of morality supposed to take place? The neuroscientific challenge to ethics focuses upon our intuitions. Neuroscience, its proponents hold, shows that our moral intuitions are systematically unreliable, either in general or in some particular circumstances.