defense of the view. Furthermore, authors writing on normative ethics often accept methodological intuitionism as they present allegedly obvious or intuitive examples or thought experiments as support for their theories. Definitional issues Because it was not until Sidgwick that it was clear there were several distinct theses sharing the label "ethical intuitionism", the term has developed many different connotations. This is liable to cause confusion; for example, G.E. Moore's Principia Ethica is often considered a locus classicus defense of ethical intuitionism, yet Moore explicitly refuses the label because of the large number of differences between his own views and traditional intuitionists. Inessential connotations Traditionally, intuitionism was often understood as having several other commitments: Moral realism, the view that there are objective facts of morality (as held by Mark Platts). Ethical non-naturalism, the view that these evaluative facts cannot be reduced to natural fact. Classical foundationalism, i.e., the view that intuited moral beliefs are: infallible (indefeasible), indubitable (irresistibly compelling), incorrigible, certain, or understandable without reflection. The view that moral properties are "simple" (as held by G.E. Moore). The view that moral truths are knowable only by intuition. However, none of these positions are essential to the view; most ethical intuitionists (such as G.E. Moore and W.D. Ross) simply happen to have held those views as well. Furthermore, intuitionists are often understood to be essentially committed to the existence of a special psychological faculty that reliably produces true moral intuitions. Few intuitionists, however, have explicitly required such a faculty exist, and some, such as Richard Price, would have explicitly denied it exists. Pluralism Secondly, sometimes the term "ethical intuitionism" is associated with a pluralistic, deontological position in normative ethics, a position defended by most ethical intuitionists, with Henry Sidgwick and G.E. Moore being notable exceptions. "Intuitivism" Robert Audi (2004, Ch. 1) points out that in applied ethics, philosophers frequently appeal to intuitions to justify their claims, even though they do not call themselves intuitionists. Audi hence uses the label "intuitivists" to refer to people who are intuitionists without labeling themselves as such. On this broad understanding of intuitionism, there are only a few ways someone doing moral philosophy might not count as an intuitionist. First, they might really refrain from relying on intuitions in moral philosophy altogether (say, by attempting to derive all moral claims from claims about what certain individuals desire). Second, they might deny foundationalism in favor of (say) coherentism.