Moral skepticism is usually defined as the denial of an objective basis of morality. Contemporary defenders of moral skepticism, such as J.L. Mackie in Ethics: Inventing Right and Wrong (1977), see the issue as principally a metaethical one: are there independent moral facts? Is there a special ontological realm in which moral universals reside? This is distinct from the normative issue which concerns whether one holds to a conventional set of moral guidelines (such as prohibitions against lying or stealing). 17th and 18th century British discussions of moral skepticism similarly focused on the metaethical and ontological question. Even if a philosopher advocated a traditional set of normative guidelines, denying the independence of moral facts implied that the guidelines were only a matter of custom, and could change at a future time. Thus, in the 17th and 18th century context, the term "moral skepticism" was an abusive label which signified that a moral theory presented a danger to traditional moral standards.
What counts as a "moral fact" or an "objective basis of morality" depends on historical context. For example, an 18th century theory which reduced morality to human instinct would be exceedingly skeptical by their standards, but would be considered optimistic by our own. To know what it means to call a philosopher of that period a moral skeptic, then, requires understanding what counted for them as an "objective basis of morality." The phenomenon of moral obligation involved issues at several levels: God's moral mandates, natural laws, universal moral relations, human moral intuition, and human moral motivation. Objectivity was a factor at all of these levels. At the top of the list, perhaps the most objective view was that moral principles are simply commanded by God and their existence depends directly on God's will. William Law offers such an argument in his Essay on the Origin of Evil (1729). Next on the list is the natural law theory, especially as offered by Hugo Grotius in de Jure Belli et Pacis (1625). Grotius extends the ancient Roman notion of judicial natural law to the ethical realm, governing all obligatory behavior. Like mathematics, moral natural laws are rational principles, known a priori, and unalterable even by God. A variation on the natural law view was the eternal fitness theory of moral obligation, as offered by Samuel Clarke in A Discourse concerning the Unchangeable Obligations of Natural Religion (1706). For Clarke, moral conduct is proper when it fits or corresponds with universal moral relations. Such fitness is apparent to all rational beings and, again, the universal moral relations themselves are unalterable by God.
The next level of issues is epistemological and involves how we acquire knowledge of moral truths. Rationalists such as Grotius and Clarke contended that we grasp them purely rationally, just as we intuit mathematical truths. Riding on Locke's account of sense perception, empirically-oriented theorists argued that we perceive moral truths through an internal moral sense. This is the view of the Earl of Shaftesbury in his Characteristics (1711), Joseph Butler in his Fifteen Sermons (1726), and Francis HUTCHESON in his Illustrations on the Moral Sense (1755). The final issue of moral obligation involves our motivation to act morally. Rationalists such as Clarke argued that the intellectual grasp of the moral relations themselves is sufficient motivation. In his Divine Legation (1738), William Warburton maintains that God's mandate is required as the prescriptive foundation of morality, although moral universals themselves exist independently of God. Others argued that moral motivation is grounded in human psychology -- either natural or learned inclinations.
Given these differing issues, moral skepticism involved taking an anti-rationalist, anti-objectivist, or anti-theist stance on several (although not necessarily all) of these topics. The first philosopher of the modern period branded a moral skeptic in the above sense was Thomas HOBBES, whose skeptical views appear in Leviathan (1651). Moral values for Hobbes are derived from social agreement and motivated by self-interest alone. Although Hobbes makes verbal concessions concerning divine moral mandates, morality is functionally a societal creation. He describes society's moral principles as natural laws, but they are not grounded in the fabric of the universe as Grotius believes. Knowledge of the moral laws is arrived at through reasoned deductions given our social condition; however, such moral reasoning is not a matter of a priori intuition about the fixed nature of the universe. Finally, and most importantly, the motivation for moral conduct is based on self-interest -- not on the rational grasping of the moral laws themselves, or divine mandates. Hobbes thus runs counter to moral objectivism in virtually every possible way. For almost 100 years his name was synonymous with moral skepticism and his theory was the principal target for succeeding moral philosophers.
Despite LOCKE's anti-rationalist orientation, in matters of morality he is anything but skeptical. The moral law is ultimately the law of God and, like mathematics, "morality is capable of demonstration" (Essay 4:12:8). Further, divine rewards and punishments are important motivators for proper conduct.
Early moral sense theorists such as Shaftesbury came under mild attack from rationalist moral philosophers. In his Foundation of Moral Goodness (1728), John Balguy charges that the moral sense theory undermines the objective nature of morality by making it depend on our sensations. However, few could charge moral sense theorists with moral skepticism. Shaftesbury, for example, argues for the objectivist position that morality is grounded "in the nature of things" (Characteristics, 2:267). Further, our instinctive social inclinations (as opposed to our selfish ones) are the natural foundation of moral motivation. Butler argues Similarly that our more altruistic natural inclinations motivate us.
With the publication of The Fable of the Bees; or Private Vices, Public Benefits (1714), Bernard Mandeville came to share Hobbes's title as a moral skeptic. Through a poetic allegory, Mandeville argues that individual vices frequently produce public benefit. For example, envy, vanity, and love of luxury make people spend, and this is necessary for profitable trade. So too with even crimes and wars. Mandeville wrote for a degree of shock value and does not offer a systematic account of moral obligation. However, he shared Hobbes's view that we are driven by self-interest, and he attacked Shaftesbury's contention that we have instinctive social inclinations. BERKELEY sharply criticized Mandeville in Dialogue Two of his Alciphron (1732). In that work Berkeley bases morality on an intellectually perceived beauty of proportionality in "a Providence inspecting, punishing, and rewarding the moral actions of men" (Alciphron 3:10). Thus, Berkeley is allied with the moral objectivists.
With the publication of Book III of Hume's Treatise of Human Nature in 1740, moral skepticism took a more precise form. Hume opens the work insisting that moral judgments do not involve either rationally grasping moral relations or empirical illumination by a moral sense. Further, God plays no role as either author or motivator of morality. Like Hobbes, our motivation to be moral is based on our psychological makeup. However, for Hume, the most important of our moral motivations are artificially instilled, such as our inclinations towards justice, chastity, and political allegiance. Hume was thus quickly accused of "sapping the foundations of morality" (William Wishart, in A Letter from a Gentleman, 1745). When Hume popularized his moral theory in An Enquiry Concerning the Principles of Morals (1751), his discussion of artificially instilled motives was subdued, and his attack on moral relations was placed in an appendix. Emphasis was placed instead on the useful and agreeable consequences of an agent's action as they spark a spectator's moral approval (this discussion formerly appeared only at the close of Book III of the Treatise). The change of emphasis prompted a reviewer to write that the Enquiry was "free from that sceptical turn which appears in his other pieces." The change in emphasis also redirected British moral theory insofar as the notion of useful consequences (i.e. utility) became the litmus test of proper moral conduct.
BENTHAM adapted Hume's theory of utility in his Principles of Morals and Legislation (1789). Not only does Bentham dismiss ontological discussions of moral relations and the moral sense, but he rejects the relevance of any discussion of the psychology of moral motivation or moral perception. For him, pleasing consequences are all that matter, since only these are empirically quantifiable. Bentham's position was no less "skeptical" than Hume's rejection of moral relations. However, the tide had already turned away from the earlier rationalist and objectivist moral ontologies. By the mid 19th century, MILL could freely argue in Utilitarianism (1863) that education (convention) was the principal motivating force behind our pursuit of general happiness. Although Mill's position spawned criticism, moral skepticism was not one of the charges.
Moral skepticism in the early 20th century empirical tradition involved
issues of language as much as ontology. The key representatives are A.J.
Ayer in Language, Truth and Logic (1936) and C.L. Stevenson in Ethics
and Language (1944). For them, moral utterances do not even rise to
the level of factual statements about the world; instead, such utterances
are noncognitive uses of language, mere expressions of feelings, or mere
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Schneewind, J.B., "Natural Law, Skepticism, and Method," Journal of the History of Ideas 52 (1991): 289-308.
Fieser, James, "Is Hume a Moral Skeptic?" Philosophy and Phenomenological
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