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Broad, Charlie Dunbar (1887–1971)


Charlie Dunbar Broad, the English epistemologist, historian of philosophy, moral philosopher, philosopher of science, and writer on the philosophical aspects of psychical research, was born at Harlesden, now a suburb of London. The only child of middle-class parents in comfortable circumstances, he received a good education at Dulwich College. With his special interest and ability in science and mathematics he won, in 1905, a science scholarship to Trinity College, Cambridge, with which Broad's philosophical career was to be chiefly associated. Despite success in his work at Cambridge, he became convinced that he would never be outstanding as a scientist and turned to philosophy, in which he took first-class honors with special distinction in 1910. A year later he was elected to a fellowship at Trinity because of a dissertation that became his first book, Perception, Physics, and Reality (Cambridge, U.K., 1914).

From 1911 to 1920 Broad was at the University of St. Andrews, first as assistant to G. F. Stout, the professor of logic and metaphysics, then as a lecturer at Dundee. During World War I, he combined his lecturing duties with work for the Ministry of Munitions in a chemical laboratory. He followed C. Lloyd Morgan in the chair of philosophy at the University of Bristol in 1920, but after a few years he returned to Trinity College to succeed J. M. E. McTaggart as lecturer in moral science. In 1933 Broad somewhat reluctantly became Knightbridge professor of moral philosophy. Until his retirement in 1953, Broad had not traveled outside Great Britain except for periodic visits to Scandinavia, in particular to Sweden, a country whose people, life, and language had long attracted him. Broad's encouragement of Swedish philosophers and philosophy led to his being generously honored by the academicians of that country. In Britain his services to philosophy were recognized by bestowal of most of the honors available to a don so secluded from public activity.

At Cambridge, Broad was most influenced by his teachers, McTaggart and W. E. Johnson, and by Bertrand Russell and G. E. Moore. These four men, with the important additions of Stout and A. E. Taylor at St. Andrews, represent in the diversity of their thought something of the extraordinary range of Broad's own interests. Among British philosophers of this century, no one, including Russell, published so much on so many different philosophical topics. The largest part of Broad's writing falls within the theory of knowledge and the philosophy of scienceprovided that we assign some of the problems of traditional metaphysics to these two fieldsalthough he also wrote extensively, if less systematically, on ethics and on the life and thought of such scattered figures as Francis Bacon, Isaac Newton, Butler, and Immanuel Kant.

The ample scope and scale of Broad's work were displayed early in his career. Within his first three years of serious publication, he had produced almost two dozen reviews of widely different books, essays on "The Doctrine of Consequences in Ethics" (International Journal of Ethics 24 [April 1914]: 293320) and "Lord Hugh Cecil's 'Conservatism'" (International Journal of Ethics, 23 [July 1913]: 396418), a critical notice of Meinong's Über Annahmen (Mind, n.s., 22 [January 1913]: 90102), and his own first volume, which discussed the relation between causation and perception. This catholicity of interest remained apparent for the next fifty years, despite Broad's confession in the autobiographical chapter of The Philosophy of C. D. Broad that some time after his acceptance of the Knightbridge chair he gave up philosophy in all but title and routine: "I no longer believed in the importance of philosophy, I took little interest in its later developments, and I knew very well that I at least had shot my bolt and had nothing further of value to contribute."

The most curious feature of this confession is that it makes the development of ennui coincide with a period of considerable publication by Broad. The 800 pages of the second volume of his Examination of McTaggart's Philosophy (Cambridge, U.K., 19331938) were written at this time, as were his essays on John Locke (Hibbert Journal 31 [January 1933]: 249267) and Henry Sidgwick (ibid., 37 [October 1938]: 2543), his inaugural lecture on determinism, a number of papers given to the Aristotelian Society, and a spate of notes on psychical phenomena. Broad's changed attitudes and feelings toward his chosen field had little substantial effect on the work he contributed to it.

Theory of Knowledge

Broad's writings on perception and knowledge, like the rest of his work, form neither a system nor a set of unequivocal answers to a group of related questions. For every philosophical position there were always reasons pro and con; and on any given issue Broad often found it difficult to decide where the weightier reasons lay.

sense data

Thus, following Stout, and ultimately Locke, in distinguishing between the odors, noises, and colored patches that we sense and the physical objects like coins and books that we perceive, Broad gave rather cautious support to a version of the causal theory of perception. There are, he thought, two kinds of particulars involved in perceptionpersistent substances (bodies) with properties like shape, size, inertial mass, and spatial position; and the "sense-qualified occurrents" of which we are immediately aware in sensing, as when we see the upper surface of a dinner plate. Broad argued that visual sense data, or sensa as he called them, at least are never, in fact, identical with, or parts of, the surface of the physical object that is seen. If we recall that the sense data obtained by a given person in looking at the same surface from different positions and angles form a continuous series, and that the velocity of light is finite, it is reasonable to believe that at least some of the properties of sense data must be different from those of their correlated bodies, that a penny, for example, retains the same size and shape while our sense data of it change in these respects as we alter position. The greater the distance between our eyes and the body seen, the more obvious it is that the properties of the body and of our sense data must differ.

It is likewise reasonable that if this difference sometimes holds, it must always hold; for there is no gap in the continuity of conditions in which we obtain sense data of a particular surface that would allow us to identify only some of the sense data with that surface. As underpinning for this sharp distinction, Broad tried to establish that a sense datum must have all the properties that it is sensed as having, although it may also have unnoticed properties; that unsensed sense data can exist; and that the word sensation refers both to bodily feelings and to "genuine sensations," the former of which are not, although the latter are, analyzable into an act of sensing and its object, the sense datum.

In general, Broad treated these claims about the existence and properties of sense data as being empirical ones, and so was led to a similar treatment of such questions as: Are sensa qualitatively mind-dependent? Can two people sense the same sensum? How long can a sensum last? Do we infer from the properties of our sensa to the properties of physical objects? How much resemblance is there between the properties of sensa and the properties of physical objects? In his "Reply to Critics," written late in his career, Broad indicated that he did not feel the force of the view, made familiar by G. A. Paul and A. J. Ayer, that these questions can be answered only by decisions in particular cases or else are misconceived, since the sense-data theory is simply an elaborate terminological proposal for dealing with the argument from illusion. Nor did he recognize the radical criticism that this view offered of his own attempts to deal with sense data as private objects interposed between human observers and the unobservable physical world. The latter is the "remote causal ancestor" of our sensations, he thought, and the kind of isomorphism one must postulate between the properties of sense data and the properties of "the hypothetical system of physical things and events" he was "willing to leave to experts to decide."

the mind-body problem

In his discussion of the mind-body problem, Broad set out to produce a theory that would account for the apparent fact that brain events are a necessary condition of mental events, and also leave open the possibility that some mental events occur after the death of their associated bodies. He suggested that minds are the result of two componentsa nervous system, and a "psychogenic factor," which is modified by experience and capable of persisting after bodily death. Since no other properties are assigned to the psychogenic factor, nor is its relation to the brain described, the factor remains unobservable, either directly or indirectly; and the parent theory is obviously ad hoc. Broad would have welcomed a theory that was more open to experimental testing; although he distinguished metaphysical from scientific theories by the latter's susceptibility to such testing. He was thus in the position of answering the philosophical question, How are bodies related to minds? with what was, by his own criteria, an inadequate scientific theory. Just as he took sense data to be private objects whose properties could be investigated by introspection, so he took the mind-body relation as being similar to the relation between a visible body and an invisible onea relation open in theory, if not in practice, to empirical investigation.

general explanatory principles

Closely related to this treatment of philosophical problems was Broad's attempt, throughout his writings, to isolate a set of very general principles that would be both necessarily true and genuinely explanatory of the most pervasive and important features of the world. Broad was not convinced either that every necessarily true statement is analytic or that every synthetic statement is testable by means of perceptual experience. He thought that there might well be propositions, such as "The cause of any change contains a change as an essential factor," which are syntheticinformative about the worldbut necessarily true. The denial of this proposition is not self-contradictory, so the proposition cannot be analytic; yet a counterexample is impossible to imagine, so the proposition, rather than being an ordinary empirical one, is self-evidently true. Propositions as general as this, Broad half suggested, are the appropriate axioms of metaphysical theories, theories whose results he compared unfavorably to the "beautiful and surprising consequences" deduced from the premises of geometry and such physical premises as the "entropy principle." Broad's pessimism about the utility of deductive metaphysics seems to have been the outcome of a desire to treat speculative philosophy as a suprascience, one that accounted for our most general concepts, such as cause, substance, potentiality, and actuality, in much the same way that physics accounted for such less general concepts as velocity, mass, simultaneity, and the atom.

a priori concepts

This distinction between the concepts dealt with by the sciences and those more general ones dealt with by philosophy has its parallel, and perhaps its source, in the distinction drawn by Broad between empirical and a priori (nonempirical) concepts. He believed that the simplest empirical concepts, for example, the ideas of red or yellow, are formed by our contrasting and comparing many different red or yellow objects. Eventually, we abstract the required quality from all other qualities and from any particular substance in such a way that we are able to think of the quality in the absence of any instance or image of it. In thus accepting the traditional story of the genesis of empirical concepts, Broad hesitated between the two equally ancient views of how we form a priori concepts. The first view is that we have innate dispositions to form specific ideas like those of cause, substance, and rightness as the result of having certain kinds of experiences. The second is that we have "a general power of non-perceptual intuition," distinct from our ability to have sense perceptions and to introspect, which allows us to intuit such relations as causation and rightness whenever we have the appropriate kinds of experiences to stimulate the power.

A standard criticism of these theories of concept formation is that the story about abstraction is logically circular; and that the accounts of a priori concepts apply equally well or little to empirical ones, so that Broad's distinction between the two cannot be drawn. The abstraction story is circular because in order to compare and contrast one color with another we must already have the ability to recognize and distinguish those colors. Yellow objects that are to be compared must be seen as yellow before the suggested procedure can begin. Hence, we can rightly claim that innate ideas or nonempirical intuitions are needed for the concept of yellow as they are for concepts like that of substance.

However, thinking of an absent quality yellow is not the intellectual analogue of sensing a yellow patch, for thinking of yellow is not a matter of "contemplating the characteristic" yellow, as Broad once assumed it was. Noting the logically necessary relations between concepts, for example, that all yellow things must be colored, is not like having a sense datum and noting that in it a red patch borders on a yellow patch. Granting these two points, as Broad did in his "Reply to Critics," would make it less plausible to hold that some synthetic propositions may be necessarily true. For once we abandon the sense-datum picture of logical necessity, there is little temptation to appeal to self-evidence (the intellectual sensing of universal connections) in support of metaphysical principles.

Psychical Research

Broad often urged philosophers to take something of his own keen interest in psychical research. He claimed that no one could answer the question as to whether any person actually has the power of paranormal precognition without having made a careful study of the available evidence; but most philosophers obviously considered this to be a scientific task for psychologists. In the absence of any encouragement from scientists, few philosophers would join Broad in discussing the further question, which chiefly interested him, How does the existence of supernormal precognition affect such philosophical topics as causation, the mind-body problem, immortality, and sense perception? Suppose we took seriously the suggestion that each person has an extended but intangible and invisible body as well as his ordinary body and that the invisible body puts forth pseudopods that touch and affect external objects. The existence of such a body would certainly alter a number of our views on topics like causation and the mind-body problem. But exactly how they were altered would depend on such factors as the degree of control we could exert over our invisible bodies, whether they survived our corporeal bodies, and what sort of knowledge we could have of our intangible bodies.

Thus until there is scientific agreement on what has been established concerning paranormal cognition, it is difficult to say how its existence would affect philosophical discussion. What can undoubtedly be done is to consider whether the notion of supernormal precognition is logically coherent. Broad thought that it is and tried to rebut arguments that it is self-contradictory to speak of precognizing something that does not yet exist as well as arguments that paranormal precognition makes an effect precede its causecorrectly guessing a card symbol would be influenced by what is to be known later about the card. However, showing that paranormality is logically possible does nothing to advance its claims over alternative hypotheses in the explanation of unlikely experimental data, data that may be unlikely because of selective sampling alone.

Probability and Induction

Although Broad's two papers titled "Induction and Probability" gave what will probably be a definitive expression to their point of view, they were overshadowed by the simultaneous appearance of J. M. Keynes's A Treatise on Probability. In much the same way, Broad's Scientific Thought (London, 1923)perhaps his best bookwas neglected after the publication, a few years later, of Russell's The Analysis of Matter. Broad argued that the degree of belief we give to well-established inductions cannot be justified "by any known principle of probability unless some further premise about the physical world be assumed." Yet this premise is notoriously difficult to state. If induction is to be a rational procedure, nature must consist of a few kinds of substances that combine in various lawlike ways and thus produce variety in a finite world. In brief, we need Keynes's principle of limitation of independent variety. Without such a principle we cannot make use of inductive analogies, for they assume that future cases will resemble past cases, or in other words, that no one object has an infinite number of independent qualities or is producible by an infinite number of different causes. In "The Principles of Problematic Induction" (PAS, n.s., 28 [19271928]: 146), Broad went on to consider, and answer affirmatively, the question whether we can know that nature has this desirable structure.

Thus, Broad held that the problem of justifying inductive inferences is a genuine one. He thought that the two questions, What is meant by calling this inductive belief well-supported? and What makes induction a valid procedure? have similar answers. Each question requires us to state the criteria by which we can distinguish sound from unsound inferences, and these criteria will enable us to provide the necessary and sufficient conditions for well-grounded inferences. Such conditions must in turn be based on fundamental principles that will serve as general premises in every sound inductive inference. This last step of Broad's claim has been much criticized as confusing two quite different issues. The first concerns the empirical statement, for which there is ample evidence, that nature is so organized that in the future at least some of our inductive beliefs will be correct. The second concerns the logically necessary truth that induction is a rational procedure; for we could not have an inductive policy that was both successful and irrational, that is, not supported by good evidence. What we mean by "rational inductive procedure" is one that is well supported by evidence. It is this support that "justifies" the policy in the only permissible sense of "justify." The structure of nature is known inductively and so cannot itself be referred to for support of the inductive procedure; nor is there any need to do so. The only justification we require is the success of the policy, and that we already have.


On the problems of ethics, Broad showed a cautious hesitancy to commit himself. Two of his late papers, "Some Reflections on Moral-Sense Theories in Ethics" (PAS, n.s., 45 [19441945]: 131166) and "Some of the Main Problems of Ethics" (Philosophy 21 [July 1946]: 99117), have been widely read; but they provide only hints as to Broad's own views. As in the early chapters of Five Types of Ethical Theory (London 1920), on such writers as Benedict de Spinoza and David Hume, Broad classified types of ethical theories, exposed their assumptions, and drew out their logical implications, without committing himself. For example, in his paper on moral-sense theories he distinguished three analyses of "That act is right": The sentence does not express the speaker's judgment, but his emotions or desires or commands; what is expressed is a judgment about "certain human experiences, certain sensations or emotions or desires," that is, a "moral feeling"; and a judgment is made that ascribes a property like "what it is fitting to approve" or "conducive to social stability," properties independent of the speaker's opinions, desires, or feelings.

In his "Reply to Critics" Broad said that theories of the second and third types must admit the existence both of nonempirical concepts of moral attributes and of synthetic a priori propositions like "any act of promise-breaking tends as such to be wrong." Since he was not convinced that there were no such concepts and propositions, he was able to sympathize with theories of these types, as well as with theories of the first type. But to the question, does "That act is right" express a judgment, a feeling, or a command? Broad could only reply, "I have no definite opinion." He was similarly undecided on the question whether ethical terms such as wrong and duty stand for properties, and if so, exactly what sort of properties these might be. His attitude here, as to many other philosophical problems, resembled that of a prudent scientist awaiting further evidence before coming to a decision.

Broad had no "philosophy" in the sense of a deeply original way of interpreting and dealing with the issues of his field. He was a scientist manqué who took up philosophical problems much as he found them, leaving them classified and more manageable but not transformed. His impressive ability to understand and recast the most difficult arguments, the elegance of his writing, his unrivaled thoroughness and lucidity, were placed at the service of other people's questions rather than his own.

See also Ayer, Alfred Jules; Bacon, Francis; Ethics, History of; Hume, David; Induction; Innate Ideas; Kant, Immanuel; Keynes, John Maynard; Locke, John; McTaggart, John McTaggart Ellis; Meinong, Alexius; Mind-Body Problem; Moore, George Edward; Newton, Isaac; Parapsychology; Precognition; Probability and Chance; Russell, Bertrand Arthur William; Sensa; Sidgwick, Henry; Spinoza, Benedict (Baruch) de; Stout, George Frederick; Taylor, Alfred Edward.


Broad's other books include The Mind and Its Place in Nature (London: Kegan Paul, 1925), his most characteristic work, and Lectures on Psychical Research (London: Routledge, 1963). Some of his essays have been collected in two volumes, Ethics and the History of Philosophy (London: Routledge, 1952) and Religion, Philosophy, and Scientific Research (London: Routledge, 1953). His two papers titled "Induction and Probability" appeared in Mind 27 (1918): 389404 and 29 (1920): 1145. There is a complete bibliography up to 1959 in The Philosophy of C. D. Broad, edited by P. A. Schilpp (New York: Tudor, 1959), which also contains 21 essays on his work by various philosophers, Broad's "Reply to Critics," and his "Autobiography." A critical examination of Broad's theory of perception is given in Martin Lean, Sense Perception and Matter (London: Routledge and Kegan Paul, 1953).

other recommended works by broad

The Nature of Existence (1921), edited by John McTaggart Ellis McTaggart. Northampton: John Dickens, 1968.

Induction, Probability, and Causation: Selected Papers. New York: Humanities, 1968.

Broad's Critical Essays in Moral Philosophy, edited by David Ross Cheney. London: Allen and Unwin; New York: Humanities Press, 1971.

Ethics. Edited by Casimir Lewy. Dordrecht; Boston: M. Nijhoff; Hingham, MA: Kluwer, 1985.

Robert Brown (1967)

Bibliography updated by Michael J. Farmer (2005)

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