 At any rate, fair or not, Sidgwick’s reconciliation of intuitional morality and utilitarianism obviously deploys a sophisticated form of intuitionist epistemology, one allowing for the fallibilism of its conclusions. He formulates four criteria or conditions “the complete fulfillment of which would establish a significant proposition, apparently self-evident, in the highest degree of certainty attainable: and which must be approximately realised by the premises of our reasoning in any inquiry, if that reasoning is to lead us cogently to trustworthy conclusions” (Sidgwick 1874 [1907: 338]). The first, often called simply the “Cartesian Criterion,” demands that the “terms of the proposition must be clear and precise,” and the second requires that the “self-evidence of the proposition must be ascertained by careful reflection,” which is especially important in ethics because “any strong sentiment, however purely subjective, is apt to transform itself into the semblance of an intuition; and it requires careful contemplation to detect the illusion” (Sidgwick 1874 [1907: 339]). Third, the “propositions accepted as self-evident must be mutually consistent,” since it “is obvious that any collision between two intuitions is a proof that there is error in one or the other, or in both.” (Sidgwick 1874 [1907: 341]). And fourth, since “it is implied in the very notion of Truth that it is essentially the same for all minds, the denial by another of a proposition that I have affirmed has a tendency to impair my confidence in its validity.” This last adds an important social dimension to Sidgwick’s epistemology: “the absence of such disagreement must remain an indispensable negative condition of the certainty of our beliefs,” for “if I find any of my judgements, intuitive or inferential, in direct conflict with a judgment of some other minds, there must be error somewhere: and if I have no more reason to suspect error in the other mind than in my own, reflective comparison between the two judgments necessarily reduces me temporarily to a state of neutrality” (Sidgwick 1874 [1907: 341–42]). In other, more purely epistemological works, Sidgwick collapsed the first two conditions into one, such that his philosophical intuitionism involved the three-pronged demand for clarity and ability to withstand critical reflection, consistency or coherence, and consensus of experts. He was also apt to explain that these conditions only afforded the best means for reducing the risk of error, rather than establishing indubitable truth. On this count, such posthumous works as Lectures on the Philosophy of Kant (1905) and Philosophy, Its Scope and Relations (1902) provide important supplements to the Methods. Singer (2000) provides an excellent collection of those of Sidgwick’s essays and reviews most relevant to the Methods.