A central theme in Thomas Reid's Essays on the Active Powers of Man (1788) is that, since we are not born with moral sensitivities or dispositions, an account of their development is in order. For Reid, a key factor that enables moral sensitivities to make an early entrance is the young child's ability to communicate sentiments with others. Reid astutely observes that “[…] we can perceive some communication of sentiments between the nurse and her nursling, before it is a month old” (AP, 333). This communication occurs near the beginning of a path from which slowly emerges what Reid calls a person's conscience, a moral sense that guides one's moral attitudes, beliefs, and actions—as well as enable moral exchanges with others.

Thus, for Reid, a child's communication with others has a very early beginning. When morally tinged communication begins is uncertain, but this also is early. Although many of our first moral beliefs and dispositions have strong staying power throughout one's life, this does not imply that we must have also accepted some overriding moral theory, consciously or otherwise, to serve as a grounding for those beliefs and dispositions. Nor, Reid thinks, is the absence of such a theory in itself a moral shortcoming.

Reid's discussion of the moral development of children is an extension of his view that morality is for everyone. By attending to the developmental process children go through, he focuses on the essential roles of both reason and sentiment in morality and their deep roots in our natural constitution. As Reid's discussion of moral judgment makes clear, reason and sentiment work together in moral agents whose “seeds of moral discernment” need careful cultivation and nurturing. Finally, attending to this developmental process helps Reid explain why he holds that theories of morality need to defer to practical, common sense when the latter is threatened by the former.

Reid makes a distinction between a “theory of morals” and a “system of morals.” The first attempts to provide “a just account of the structure of our moral powers; that is, of those powers of the mind by which we have our moral conceptions, and distinguish right from wrong in human actions” (AP, 282). This is as difficult an area of philosophical inquiry as any, he says.