Among ethical theories debated in the first half of the 20th cent. were instrumentalism (John Dewey), for which morality lies within the individual and is relative to the individual's experience; emotivism (Sir Alfred J. Ayer), wherein ethical considerations are merely expressions of the subjective desires of the individual; and intuitionism (G. E. Moore), which postulates an immediate awareness of the morally good. Agreeing with Moore that the morally good is directly apprehended through intuition, deontological intuitionists (H. A. Prichard, W. D. Ross) went on to distinguish between good and right and to argue that moral obligations are intrinsically compelling whether or not their fulfillment results in some greater good.
Important ethical theories since the mid-20th cent. have included the prescriptivism of R. M. Hare, who has compared moral precepts to commands, a crucial difference between them being that moral precepts can be universally applied. In his arguments for virtue ethics, Alasdair C. MacIntyre has cautioned against unbridled individualism and advocated correctives drawn from Aristotle's discussion of moral virtue as the mean between extremes. Thomas Nagel has held that, in moral decision making, reason supersedes desire, so that it becomes rational to choose altruism over a narrowly defined self-interest. See also bioethics.