Moral skepticism

Moral skepticism (or moral scepticism) is a class of metaethical theories all members of which entail that no one has any moral knowledge. Many moral skeptics also make the stronger, modal, claim that moral knowledge is impossible. Moral skepticism is particularly opposed to moral realism: the view that there are knowable, objective moral truths.

Defenders of some form of moral skepticism include David Hume, J. L. Mackie (1977), Max Stirner, Friedrich Nietzsche, Richard Joyce (2001), Michael Ruse, Joshua Greene, Richard Garner, Walter Sinnott-Armstrong (2006b), and the psychologist James Flynn. Strictly speaking, Gilbert Harman (1975) argues in favor of a kind of moral relativism, not moral skepticism. However, he has influenced some contemporary moral skeptics.

Moral skepticism divides into three subclasses: moral error theory (or moral nihilism), epistemological moral skepticism, and noncognitivism. All three of these theories share the same conclusions, which are:

However, each method arrives at (a) and (b) by different routes.

Moral error theory holds that we do not know that any moral claim is true because

Epistemological moral skepticism is a subclass of theory, the members of which include Pyrrhonian moral skepticism and dogmatic moral skepticism. All members of epistemological moral skepticism share two things in common: first they acknowledge that we are unjustified in believing any moral claim, and second, they are agnostic on whether (i) is true (i.e. on whether all moral claims are false).

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