 Many have felt that, in setting up the systematic comparison between the main methods of ethics, Sidgwick was not nearly as neutral and impartial as he thought, and in various ways slanted the discussion against a wide range of alternatives, including Aristotelian and other forms of perfectionism, Whewellian rationalism, Idealism, and more (Donagan 1977, 1992; Irwin 1992, 2007, and 2011; Hurka 2014a, 2014b). He simply dismisses the traditional philosophical concern with the “moral faculty,” explaining that he is going to leave that matter to psychologists. For Sidgwick, in any given situation, there is something that it is right or that one ought to do, and this is the proper sphere of ethics. The basic concept of morality is this unique, highly general notion of “ought” or “right” that is irreducible to naturalistic terms, sui generis, though moral approbation is “inseparably bound up with the conviction, implicit or explicit, that the conduct approved is ‘really’ right—that is, that it cannot without error, be disapproved by any other mind” (Sidgwick 1874 [1907: 27]).  On this count, at least, his student G. E. Moore was willing to declare the Methods untainted by the “naturalistic fallacy”—that is, the confusion of the “is” of attribution and the “is” of identity that supposedly infected much previous ethical theory, including that of Bentham and the Mills. And indeed, it is plain that Sidgwick parted company from classical utilitarianism in many ways, rejecting the empiricism, psychological egoism, and associationism (supposedly) characteristic of the earlier tradition. F.H. Hayward, who wrote one of the first books on Sidgwick’s ethics, famously complained that E. E. Constance Jones had missed just how original Sidgwick was: “Sidgwick’s identification of ‘Right’ with ‘Reasonable’ and ‘Objective’; his view of Rightness as an ‘ultimate and unanalysable notion’ (however connected subsequently with Hedonism); and his admission that Reason is, in a sense, a motive to the will, are due to the more or less ‘unconscious’ influence of Kant. Miss Jones appears to think that these are the common-places of every ethical system, and that real divergences only arise when we make the next step in advance. I should rather regard this Rationalistic terminology as somewhat foreign to Hedonism. I do not think that Miss Jones will find, in Sidgwick’s Hedonistic predecessors, any such emphasis on Reason (however interpreted)” (Hayward 1900–1: 361). Sidgwick himself allowed that Kant was one of his “masters,” and he was also quite familiar with the works of Hegel. Schneewind’s reading (Schneewind 1977) has stressed this influence, along with the influence of Joseph Butler, whose works persuaded Sidgwick of the falsity of psychological egoism and of the reality of other than self-interested actions (Frankena 1992). Indeed, the comparison between Sidgwick and Kant has proved to be a fertile and ongoing source of academic work on Sidgwick, and one of increasing significance (Parfit 2011; Paytas 2018)