Henry Sidgwick rose to prominence as an academic philosopher in the late nineteenth century. He was a brilliant student and following his matriculation at Cambridge he was awarded a fellowship in classics at Trinity. Ten years later he shifted his studies to moral philosophy. In the last decades of the nineteenth century, he became the leading exponent in Britain of the utilitarian approach to ethics, politics and political economy. The approach had been primarily developed by Jeremy Bentham, John Stuart Mill and David Ricardo, and Sidgwick became their disciple. His admiration of Mill, in particular, guided his work.

By following in the footsteps of Bentham and Mill, Sidgwick allied himself with the strong secular strain in British philosophy. The strain goes back to Hobbes, notwithstanding Hobbes's ambiguous relationship to Christian thought, and is generally associated with his thought, that of Hume, and that of the utilitarian thinkers on whom Hume had such a profound influence. All of these thinkers worked outside the academy. Indeed, until the founding of the University of London, now UCL, in 1826, college and university posts in Britain were closed to free thinkers, and at Cambridge and Oxford only members of the Anglican Church were eligible for fellowships. Sidgwick, whose father was a clergyman in the Anglican Church and who was raised within a strict Christian household, struggled through much of his adult life with his inability to find grounds sufficient to sustain his faith. He came to the conclusion, during the first decade of his fellowship at Cambridge, that he could no longer affirm God's existence or maintain his belief in the miracles on which Christianity is founded, and these conclusions led him eventually to resign his fellowship. The resignation was not, however, an act of defiance. Rather it sprung from a commitment to sincerity in the conduct of life and a corresponding intellectual and moral integrity for which Sidgwick had a high reputation. Because holding such a fellowship meant that one subscribed to the Church's doctrines, Sidgwick decided that he could not in good conscience continue as a fellow under that condition. And while he remained at Cambridge afterward as a lecturer, he did so in reduced circumstances. He incurred a substantial loss of income as well as the privileges the fellowship conferred.Footnote ¹ The incident tells of the signal importance in defining his life of the conflict between his intellectual integrity and his religious yearnings. While it is true that Sidgwick aligned himself with Bentham and Mill, he nonetheless remained deeply ambivalent about this alliance.

The theme of conflict between Sidgwick's intellectual and religious sides is at the heart of Bart Schultz's Henry Sidgwick: Eye of the Universe.Footnote ² Schultz, in this monumental biography, develops this theme with wonderful lucidity and attention to detail. These details include matters in Sidgwick's private life at which those of us who knew Sidgwick only from his published work would have never guessed. Schultz has extensively searched archives containing diaries, private notes, and correspondence between Sidgwick and his family, friends, teachers and acquaintances, and brought to light fascinating material about his personal relations and how their ebb and flow influenced his thought. The fragments of the diaries, notes and letters that Schultz quotes disclose not only a young man undergoing a crisis of faith and an older one immersed in efforts to reform British universities so as to make them less subject to the Church's rules, freer to promote research and teaching in accordance with academic standards, and more open to educating men and women alike, but also a man haunted by wishes to communicate with the dead and deeply troubled, at a time in England of harsh repression of homosexual love, by his sexual identity and the sexual identities of his friends. Schultz skillfully uses these materials to illuminate how the tension between Sidgwick's allegiance to intellectual ideals and the hold that religious belief continued to have on him even after he disavowed it shaped both the character of his studies and the conduct of his professional life. And in doing so Schultz also effectively reveals the warping effect of the established religion in late Victorian England on many of the educated class of Sidgwick's generation.

Above all, Schultz shows how firmly rooted Sidgwick's masterwork, The Methods of Ethics, was in this conflict.Footnote ³ That a need to square his religious beliefs with his commitment to intellectual ideals lay behind the work is readily evident in the frank admission of failure with which the first edition of Methods ends. Sidgwick had undertaken the study of ethics with the aspiration of showing the unity of practical reason. Success, Sidgwick recognized, would support belief in the moral order of the universe, and if one could come to this belief through a study of ethics that was independent of theological assumptions, one's belief in the universe's being created by a supreme being, a being who could in making the universe give such order to it, would then be well-grounded. Conversely, failure would be further reason for religious skepticism. And if the failure consisted in one's reaching the opposite conclusion, the conclusion that practical reason was divided, then one would either have to abandon reason for baseless belief in God's existence, as Sidgwick thought Kant with his postulates of rational faith had done, or else conclude that the universe was morally chaotic. Because abandoning reason was not an option for Sidgwick, his acceptance of the duality of practical reason as the conclusion of his study was a bitter concession of defeat, thus prompting the expression of despair at the work's end.

But even before Sidgwick undertook the study of ethics, he brooded over how he could live a Christian life and fulfill the duty of self-sacrifice on which it is based while pursuing his academic and literary interests. And the felt imperative to find a way to accommodate both ambitions eventually gave a significant push to the later project of reconciling utilitarian ethics with the ethics of self-interest. The importance of these personal concerns in shaping his ethical studies is well-documented in the Memoir that his wife and brother assembled after his death.Footnote ⁴ What Schultz perceptively adds to the standard narrative that one can extract from the Memoir is a fuller understanding of how these concerns grew in part out of the close friendships Sidgwick formed with other Cambridge students with whom he took part in the revival of interest in Hellenic culture that was taking place at Oxford and Cambridge and who shared with him a strong attraction to the ancient Greeks, especially Plato. Their shared admiration and desire to recover a pagan culture could only have made the conflict in Sidgwick between his Christian predisposition and his secular commitments more acute, and Schultz provides an excellent account of this effect.

How much Sidgwick's very public struggles with his loss of faith colored the perception of Methods during his lifetime – and Schultz offers some striking evidence of considerable coloration at least among younger generations of Cambridge students – is hard to tell. What is not uncertain, however, is that the work was not perceived during his lifetime as a major and lasting contribution to British moral philosophy. It was perceived rather as Sidgwick's first major work and the one that established his scholarly reputation beyond Cambridge. This at any rate is how the article on him in the 10th edition of the Encyclopaedia Britannica, published shortly after his death, describes Methods, and the description remains unchanged in the Encyclopaedia's subsequent editions at least to the 14th.Footnote ⁵ The article, which underwent a slight expansion in the 11th edition, lists Sidgwick's other treatises as among his major works and does not single out Methods, as we now do, as his masterpiece or as a more important contribution to philosophy than any of them. Indeed, in saying of his work that ‘None of [it] is more closely identified with his name than the part he took in promoting the higher education of women’ the article suggests none too subtly that the influence of the scholarly work and of Methods in particular was limited to his own time and not such as to imply great originality or fertility.Footnote ⁶

It is unremarkable, then, that attention to and interest in the ideas and arguments in Methods greatly diminished after Sidgwick's death and that the work was largely ignored in Anglo-American philosophy for much of the twentieth century. Schultz attributes this steep decline in its importance to the hostility toward Victorian thought of the Cambridge luminaries who succeeded Sidgwick – Russell, Moore, Wittgenstein, Keynes and Strachey, inter alios – and to the ascendancy of certain styles of philosophical thought, the programs of analysis championed by Russell and Moore and those programs’ successors, logical positivism and the modes of investigation developed by the later Wittgenstein, that dominated Anglo-American philosophy for more than fifty years. And he remarks as well that a ‘pervasive Bloomsbury mentality . . ., as much as anything, clouded the reception of Sidgwick during the first half of the twentieth century’.Footnote ⁷ This, however, suggests that Sidgwick's work was a precious jewel of Victorian thought that was widely admired and fully appreciated by his contemporaries and then foolishly put away in some backroom by the enthusiasts for trinkets and baubles who inherited the store and who over time forgot about the real gem that had once graced their showroom. And there is scant evidence of its ever having been so admired or appreciated during Sidgwick's lifetime. There is of course C. D. Broad's singular statement in the book on types of ethical theory that he published in 1930, his statement that Methods, as it seemed to him, was ‘on the whole the best treatise on moral theory that has ever been written’.Footnote ⁸ But unfortunately Broad's well-known partiality for the achievements of his countrymen, especially Cambridge men of Anglo-Saxon ancestry, offers a better explanation for the remark than that it reflected a once commonly held and then forgotten opinion of the work.

There is, in addition, a very good philosophical explanation for Methods's being eclipsed by advances in Anglo-American philosophy that are due to movements in the analytic tradition from Russell and Moore to Quine and Putnam. For Sidgwick based the study of practical reason that he carried out in Methods on an epistemology that increasingly became suspect in analytic philosophy and eventually discarded as obsolete. The epistemology in question is the traditional epistemology of mathematics in which the truths of a branch of mathematics are either the fundamental propositions of that branch or follow deductively from its fundamental propositions. The fundamental propositions are the branch's axioms (or postulates)Footnote ⁹ and the propositions that follow deductively from them are its theorems. Knowledge of the axioms is guaranteed by their self-evidence, and knowledge of the theorems is then guaranteed by their being logically related to the axioms. That is, because the inferences that deductive logic validates are truth-preserving, if one knows that the axioms are true, one will then know of any proposition that one has shown deductively to follow from the axioms that it too is true. I will call the conception of knowledge implicit in this epistemology the traditional intuitionist conception. It consists of, first, a distinction between what can be known intuitively and what can be known inferentially – or as Sidgwick puts it, what has self-evidence and what has demonstrative evidenceFootnote ¹⁰ – and, second, the main doctrine of traditional intuitionism, that there are in each branch of knowledge to which the conception applies propositions that have self-evidence and that constitute the source of the demonstrative evidence on which knowledge of other propositions in the branch is founded. The traditional intuitionist conception of knowledge dominated modern philosophy for at least two hundred and fifty years, beginning with Descartes, whom Sidgwick regards as having, along with Bacon, originated the methodology he uses in searching for the fundamental principles of ethical knowledge.Footnote ¹¹ Its domination began to erode only late in the nineteenth century with the controversies that arose among logicians and mathematicians over the nature and solidity of the foundations of mathematics.

Sidgwick identifies this epistemology as philosophical intuitionism. He distinguishes it from two other forms of intuitionism, which he identifies as perceptional and dogmatic. Both had important adherents in the history of moral philosophy. Perceptional intuitionism holds that ethical propositions about particular individuals, actions and events can be known intuitively. That is, one can see directly when judging a particular action, say, such as my returning a lost dog to its owner, that it is the right thing to do. One's intuition of the rightness of the action in this case is thought to be embedded in the very perception and understanding one has of my action; hence the term ‘perceptional intuitionism’ that Sidgwick coined. Dogmatic intuitionism takes as the ethical propositions that can be known intuitively general propositions that correspond to moral precepts or general moral rules, rules forbidding, requiring or recommending action of a certain type. Such propositions as killing another human being is wrong and one good turn deserves another are examples. They correspond to rules forbidding homicide and recommending acts of gratitude. Dogmatic intuitionism is the form that moral philosophers usually mean when they refer to ethical intuitionism. Until Sidgwick's critique of it in Methods, dogmatic intuitionism prevailed among the defenders of common-sense morality, who were the chief opponents of utilitarian ethics. Reid's exposition of it set an early standard in British moral philosophy. Later expositions in the first third of the nineteenth century deviated unimportantly from Reid's. Subsequently, expositions that contained Kantian elements appeared, the most important of which was produced by Whewell.Footnote ¹²

Sidgwick's distinction between dogmatic and philosophical intuitionism is essential to his argument for the compatibility of utilitarian and intuitionistic ethics. The problem with perceptional intuitionism, Sidgwick declared, was the unreliability of intuitions about the rightness or wrongness, say, of particular acts. ‘[P]articular intuitions,’ he observed, ‘do not, to reflective persons, present themselves as quite indubitable or irrefragable: nor do they always find when they have put an ethical question to themselves with all sincerity, that they are conscious of a clear immediate insight in respect of it’.Footnote ¹³ For roughly similar reasons, he then argued, the intuitions one has about the validity of general moral rules are also untrustworthy. They have the backing of common sense, to be sure, but the assent we give them by virtue of their being commonsensical shows only that they contain an intuitive element and not that, as formulated, they correspond to self-evident propositions. But even if one could achieve the precision in formulation necessary to articulating general rules that comprehended all human actions and whose validity one could be absolutely certain of, Sidgwick continued, the resulting collection of rules would still not be sufficiently unified to constitute fundamental knowledge. Rather it would be a mere ‘aggregate of precepts, which stands in need of some rational synthesis’.Footnote ¹⁴ Thus dogmatic intuitionism falls short of the standards of clarity and certainty of truth by which self-evidence is determined. The thesis is crucial to establishing the need for recourse to philosophical intuitionism, and accordingly Sidgwick devotes the extensive examination and reconstruction of common-sense morality in book III of Methods to sustaining it. Establishing that the propositions corresponding to the general rules of common-sense morality are too vague and unconnected to each other to be the axioms of ethics then gives him room to find a set of even more general principles from which these rules, once they are more precisely formulated, can be derived, and if the fundamental principle of utilitarian ethics belongs to this set, then a reconciliation between utilitarian and intuitionistic ethics becomes possible.

Philosophical intuitionism considered in the abstract is plainly an advance on dogmatic intuitionism. Schultz treats it, if I am reading him as he intends, as one of the major contributions Methods makes to moral philosophy. By being ‘complex and fallibilistic’ and by incorporating ‘coherence and consensus as criteria for reducing the probability of error’ in the determinations of self-evidence, Shultz argues, it avoids the standard objections to intuitionistic epistemology that such an epistemology merely serves to reinforce prejudice and that it fails to challenge conventional thought.Footnote ¹⁵ All of this is no doubt true, but it is not germane to the considerations in the analytic tradition that led to intuitionism's becoming a suspect epistemology. For what makes it suspect is the main doctrine of traditional intuitionism, the belief that in each branch of knowledge to which the traditional intuitionist conception applies there are propositions that are self-evident and that constitute the source of the demonstrative evidence on which knowledge of other propositions in that branch is founded. This doctrine is common to both philosophical and dogmatic intuitionism. Indeed, an epistemology like Sidgwick's that assumes that moral knowledge is grounded in the axioms of ethics could not be an intuitionist epistemology if it did not encompass the doctrine.

In epistemology, mathematics had long been the discipline whose branches served as the paradigms of knowledge that conformed to the traditional intuitionist conception. The doctrine then became suspect as a result of advances in mathematics that vitiated this conception. The advances, which began in the latter half of the nineteenth century, overturned the age-old understanding of axiomatic treatments of a field of mathematical study. In particular, mathematicians ceased to regard the axioms of an axiomatic system as being self-evident propositions. They ceased, that is, to regard self-evidence as a defining property of a system's axioms. They gave up this view once they began to construct and explore alternative systems within a single branch of the discipline. For the development of alternative axiomatic systems within a single branch, once it becomes understood as no less an exploration of the objects in a mathematical field than the development of the standard system, is devastating to the traditional intuitionist conception of the knowledge afforded by that branch.

The most influential of these constructions are the axiomatic systems for geometry that are alternatives to Euclidean geometry. In each of these alternatives, the crucial difference between it and Euclidean geometry is found in its postulate about parallel lines. In Euclidean geometry the relevant postulate is Euclid's famous parallel postulate, that given a point P and a line L that does not contain P, there exists one and only one line that contains P and is parallel to L. In a non-Euclidean geometry this postulate is replaced by a proposition that contradicts it either by denying that there is any line parallel to L that contains P or by holding that there are more than one. Since a proposition and any proposition that contradicts it cannot both be true, they cannot both be self-evident. Hence, entertaining an axiomatic system that is an alternative to Euclidean geometry means giving up the idea that to be an axiom or postulate a proposition must be self-evident. Euclidean geometry had for centuries stood as the model of a branch of knowledge that is divisible into the class of propositions that we know intuitively and the class of propositions that we know inferentially, and the development of non-Euclidean geometries meant that the defenders of traditional intuitionist epistemology could no longer invoke it to substantiate their conception of knowledge.

Of course, even after the development of non-Euclidean geometries someone might still insist that Euclid's parallel postulate is self-evident and that the contradictory propositions that are postulates in non-Euclidean systems are mere logical possibilities, as are the systems themselves. But to do so would require attributing to rational minds a special faculty for directly apprehending the nature of physical space, for otherwise it would be pointless, if not meaningless, to insist on the truth of Euclid's system and the falsity of these alternatives. And because geometry is indispensable to the study of motion in physics, any such thesis about the mind's special faculty for discerning the nature of physical space was destined to be rejected as unscientific. Natural science cannot allow appeals to faculties beyond the senses as sources of evidence of the nature of the physical world and remain distinct from occult thinking.

Analytic philosophers, chiefly under Russell's influence, thus took the development of non-Euclidean geometries as decisive evidence against Kant's thesis that mathematical truths were synthetic propositions of which we have a priori knowledge. They rejected, then, as an account of mathematical knowledge, the traditional intuitionist epistemology except as it applied to the truths of logic. While the epistemological status of geometrical propositions remained controversial, it was still commonly believed that knowledge of other mathematical propositions, those of arithmetic in particular, was a priori. Hence, again under Russell's influence (and through him Frege's), analytic philosophers took arithmetic to be reducible to logic. The program of logicism that Frege set forth near the end of the nineteenth century and that Russell continued in the twentieth was thus meant to vindicate the belief that knowledge of arithmetic truths conformed to the traditional intuitionist conception. On this program, the axioms of arithmetic were theorems of deductive logic and thus regarded as known by inference from the axioms of logic. By contrast, the latter (or other truths of logic that could serve equally well as axioms in an axiomatic systematization of deductive logic) were regarded as known intuitively. On the logicist program, they alone were self-evident propositions. Unfortunately for those who pinned their hopes on logicism, this attempt to preserve an understanding of arithmetic as conforming to the traditional intuitionist conception collapsed too as a result of Gödel's second incompleteness result. And with its collapse one could no longer look to mathematics for substantiation of traditional intuitionist epistemology. At this point its obsolescence was foredoomed.

It is somewhat ironic that Sidgwick's philosophical intuitionism, while it represents in the abstract an advance on perceptional and dogmatic intuitionism, was nonetheless more vulnerable than either of them to being swept away by the high tide of skepticism toward traditional intuitionist epistemology that the development of non-Euclidean geometries produced. Both Moore's intuitionism, which was perceptional, and that of Prichard and Ross, which was dogmatic, were able to withstand this tide. Sidgwick's, however, was not. The reason for the difference is that Moore, Prichard and Ross could prop up their theories with metaphysical and psychological theses that were alien to Sidgwick's theory. Thus Moore introduced non-natural properties, principally goodness, that we directly perceive when we judge that something is good. And Prichard and Ross appealed to a special moral faculty by which we intuit that acts of a certain kind are right or ought to be done, in the distinctively moral sense of ‘right’ and ‘ought’.Footnote ¹⁶ Since ethics is not a subject that is indispensable to the natural sciences and indeed the question of its autonomy from the natural sciences is a central one in the discipline, the introduction of non-natural properties or the appeal to a special moral faculty to preserve our understanding of it as a branch of knowledge is no threat to the stability of the natural sciences. Hence, the kind of hypothesis that would be immediately dismissed if entertained as a way to preserve pure geometry as a study of the true nature of physical space is open to consideration and argument in ethics at least as long as the question of its autonomy from the natural sciences is unsettled.

Sidgwick, however, abjured hypotheses of this kind. In the opening paragraphs of the preface to the first edition of Methods, he informs his reader that the work is neither metaphysical nor psychological. He assumes only that in any given situation calling for some action there is something that ‘it is right or reasonable to do, and that this may be known’.Footnote ¹⁷ And he then remarks that as long as no one disputes our having the capacity to know, in a given situation, what it is right or reasonable to do, then it appears to him that ‘the investigation of the historical antecedents of this cognition, and of its relation to other elements of the mind, no more properly belongs to ethics than the corresponding questions as to the cognition of space belong to Geometry’.Footnote ¹⁸ His avoidance of metaphysics and psychology, his abstaining from putting forward hypotheses about the metaphysical nature of ethical properties or the special character of our capacity to know right from wrong, was intended to keep his study free of unnecessary controversy. The study of practical reason and whether it can be unified does not require, he argued, that one take a position on questions about the nature of ethical properties or the origins of our power to make ethical judgments as long as one can regard practical reason as a part of reason and its study as no different from studies in other departments of knowledge such as logic or geometry. Thus, neutrality on these questions seemed to him well advised.

Schultz, following other recent commentators, characterizes Sidgwick's deliberate neutrality on questions about the metaphysical nature of ethical properties and the origins of our powers to make ethical judgment as creating a minimal metaethics.Footnote ¹⁹ He regards this minimalism in Sidgwick's metaethics as one of its great strengths. He too thinks it was well advised. That it may have played an important role in Methods’ falling into neglect among Anglo-American philosophers for much of the twentieth century is not something he considers. And while Schultz recognizes that the objections of analytic philosophers to traditional intuitionist epistemology have had the effect of diminishing its standing in contemporary philosophy, he believes that the targets of those objections have been weaker forms of intuitionism than Sidgwick's and that Sidgwick's philosophical intuitionism, being a significant improvement on these weaker forms, can withstand these objections. Its having been confused with these weaker forms means that its diminished standing is undeserved, and Schultz mounts a vigorous defense to show this.

Unfortunately, Schultz does not in this defense of Sidgwick's philosophical intuitionism deal with the chief grounds for skepticism about traditional intuitionist epistemology as these grounds became clear from consideration of the abandonment of this epistemology in mathematics. In mathematics it became clear that whether or not a proposition was self-evident was irrelevant to its being an axiom in an axiomatization of a branch of the discipline. Hence, the mathematical knowledge that the axiomatization represented could not be understood as knowledge that consists of knowing the truth of some of the propositions the axiomatization comprehends on account of their self-evidence and knowing the truth of the rest by virtue of their being deducible from the propositions whose truth one knows on account of their self-evidence. And if self-evidence has ceased to be a property that one needs to attribute to some mathematical propositions in order to explain mathematical knowledge, then the question that any defender of traditional intuitionist epistemology in ethics must answer is why one needs to attribute self-evidence to some ethical propositions in order to explain ethical knowledge. Schultz's defense of philosophical intuitionism nicely shows the subtleties and complexity of Sidgwick's epistemology, but it is nevertheless a defense of an epistemology that, though current and widely accepted in the nineteenth century, is now obsolete.Footnote ²⁰

Hobbes, in chapter 4 of Leviathan remarked, parenthetically, that ‘geometry . . . is the only science that it hath pleased God hitherto to bestow on mankind’.Footnote ²¹ What he meant, of course, was that the axiomatic system that Euclid expounded was the model to which anyone who aspired to expand scientific knowledge in some area should follow in setting down his discoveries. Nor was Hobbes alone among philosophers in regarding Euclid's system as a gift from God. The order and beauty in geometry that it disclosed was easily taken as the work of a supreme intelligence. I venture to speculate that Sidgwick too thought of the order and harmony that an axiomatic system disclosed in the subject it organized as evidence of a supreme intelligence. And if there is any merit to this speculation, then a certain incongruity in Sidgwick's ethics becomes explicable. For Sidgwick, having allied himself with the secular strain in British philosophy, oddly chose to defend utilitarianism, the system of ethics that, as a secular system, had long been identified as a product of British empiricism, by expounding it as the unifying element in an axiomatic system, a system that by disclosing order and harmony in the ethical regulation of human conduct provided evidence of God. Thus even in the epistemology that informs his Methods, one can find manifestation of the conflict in Sidgwick between his intellectual and religious sides.