Thus the first system he accepted was Mill's; but because he could see no reason, on Mill's view, why one ought to sacrifice one's happiness to that of others, he was 'forced to recognize the need of a fundamental ethical intuition'. (Me 7, xv-xvi.) (p.41)
Me 7, xv-xviは、第4版への緒言の後半から第6版への緒言の前半が書かれており、シュニーウィンドが引いているような記述は見当たらないのだが。
In the 1901 autobiographical statement Sidgwick tells us that after accepting Mill's ethical theory he turned to the problem of selfishness posed by Mill's psychology, and realized from trying to solve it that an intuition was required to complete the utilitarian position. (pp.42-3)
APPEALS to self-evidence and to what is intuitively given are not very satisfactory modes of solving basic philosophical problems. […] In the present chapter it is argued that Sidgwick, like Alexander Smith and William Whewell, is aware of these shortcomings of the appeal to intuition and tried to avoid them. Like Smith, he interprets self-evidence in terms of the basic operations of ordinary reasoning, applied to practice; but where Smith fails to avoid tautology Sidgwick is clearly aware of the danger. (ME 7, pp.374-9.) Like Whewell, he takes the problem to be that of working out what the most fundamental demands of reason are, given the conditions of human life; but he is more successful than Whewell in developing a solution within this framework. Though Sidgwick himself points out the Kantian affinities of his position he is by no means simply a Kantian. He is deliberately developing a traditional mode of approach to basic axioms. In doing so, he brings out distinctly new possibilities within it.