Monism and Pluralism

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How many things are there? Or how many kinds of thing? Monism is the doctrine that the answer to one or other of these questions is "Only one." Opposed to monism is the doctrine of pluralism, which is that there are many kinds of thing, or that there are many things. It will be apparent, on reflection, that this weaker form of pluralism, that there are many things, is quite consistent with the weaker form of monism, that there is only one kind of thing to which the many particular things belong. For instance, materialism, in the sense that everything existent is material, is a form of monism because it insists that all existent things are of a single kind, the material kind. Thus monism and pluralism, though opposed, do not always exclude each other.

A doctrine that might be regarded as a form of pluralism, possibly the most important form of it, is dualism, the belief that there are two things or two types of thing. In view of its importance, it will be treated below in a separate section.


"Monism" is a name for a group of views in metaphysics that stress the oneness or unity of reality in some sense. It has been characteristic of monism, from the earliest times, to insist on the unity of things in time (their freedom from change) or in space (their indivisibility) or in quality (their undifferentiatedness). Such a view of the world is already found in a developed form in the pre-Socratic philosopher Parmenides and was nicknamed the "block universe" (by Thomas Davidson, a friend of William James), that is, the universe thought of as a single closed system of interlocking parts in which there is no genuine plurality and no room for alternative possibilities. Although this world view and similar ones are now classified as forms of monism, they may not have been seen as falling into a single category at all until the term monism had itself been invented. The term was coined by Christian Wolff (16791754), and he used it only in a narrow sense, applying it to the two opposite theories that everything is mental (idealism or mentalism) and that everything is material (materialism). The term was subsequently applied to a particular doctrine of the relation between mind and matter, namely, the theory of their absolute identity (the Identitätsphilosophie so often mentioned by William James). The main proponents of this doctrine were Friedrich Schelling and G. W. F. Hegel, although it actually originated with Benedict de Spinoza and is sometimes known as the double-aspect theory. It holds that mind and body are only modes of the same substance, and it is this substance to which they are both reducible, not one to the other. A more recent version of this theory is the "neutral monism" of William James, which Bertrand Russell at one time also adopted. On the other hand, it should be noted that the Identitäts-philosophie and neutral monism differ from the "identity theory," which is a form of materialism recently set forth by J. J. C. Smart, Herbert Feigl, and others. The identity theory holds that the mind is not some third thing, some "neutral stuff" like sensation, but is literally identical with the brain.

In the nineteenth century the word monism came to be given wider application and so to have a systematic ambiguity, that is, a consistent variation of meaning according to context. Since then any theory that tries to reduce all phenomena to a single principle, or to explain them by one principle, or to make statements about reality as a whole, has been labeled "monism." The ambiguity is not harmful, provided that theories about how many substances there are (substantival monism) are distinguished from theories about what kinds of substance exist (attributive monism). This distinction also needs to be observed in the case of pluralism (see below).

Substantival and attributive monism are logically independent views, and the various possible combinations of attitude to these questions are actually found in the doctrines of major philosophers. Thus if by "substantival monism" we mean the theory that the apparent multiplicity of substances is really a manifestation of only a single substance in different states or from different points of view, then Spinoza, with his God-or-Nature, and Francis Herbert Bradley, with his Absolute, are typical substantival monists. Indeed, Part I of Spinoza's Ethics is the classic exposition of substantival monism, offering a proof that there can be only one self-subsistent and independent thing. But Spinoza rejected attributive monism, which maintains that all the substances that there are, whether one or many, are ultimately of a single kind. He believed in an infinity of real attributes. An opposite case is that of Gottfried Wilhelm Leibniz, who rejected substantival monism but accepted a monism of attributes, for in his philosophy all the monads are of one kind, being souls.

A further possible doctrine, that might be called partial monism, is the belief that even if there is more than one realm of being, there is only one substance within some particular realm. For example, René Descartes, who is the classic dualist insofar as he divides the world into the two realms of mind and matter, accepted partial monism about matter, which he treated as a unitary substance, while he rejected partial monism about minds.

If monism in one or other of these various senses keeps on turning up in quite diverse philosophical systems, that is not really surprising. A striving for unity in a world description, perhaps for the sake of easier comprehensibility and greater economy of explanation, perhaps resulting from the direct appeal of simplicity, is a perennial urge in human thought. Even a substantival pluralist, Leibniz for instance, usually maintains that the plurality of substances in his world do form a systematic unity "ideally" or when looked at from the viewpoint of an omniscient being. To many minds, a monistic theory is always the most attractive option if the obstacles to holding it can be removed.


Dualism is the position of those thinkers who find some radical and irreducible difference in the world, an insuperable gulf between two realms of being. Any philosophical system that divides the world into two categories or types of thing, or uses two ultimate principles of explanation, or insists that there are two substances or kinds of substance, is a form of dualism. (The same ambiguity is found here as with the other labels.) Even the presence of a cardinal though not all-embracing contrast in a philosophical system may justify calling it a dualism in a looser sense, as when we speak of the dualism of Plato, in whose works the world of flux presented to the senses is sharply contrasted with the world of Forms known by the intellect, or when we consider the corresponding dualism of phenomena and noumena in Immanuel Kant.

Although superficially dualism can be seen as a special case of pluralism, it should be clear from the foregoing that it has often been, so to speak, the expression of failed monism. Nor is it merely that monism has to many minds the attractiveness described earlier; the dualistic position is inherently unstable and puzzle-generating. Once we have divided the world into twofor example, into natural and supernatural, temporal and eternal, material and mental, particular and universalwe have on our hands the problem of the relation between the two resulting worlds. These bridging problems have bulked large in both ancient and modern philosophy. Even though dualism of mind and body, for instance, may be said to reflect the time-honored view of common sense and was adopted by philosophers at least as early as Anaxagoras, Descartes's version of it, with thinking substances operating mysteriously on bits of extended substance, set the problem for all subsequent philosophers until Gilbert Ryle, in The Concept of Mind (1949), dismissed it as a "category-mistake."

There may be thinkers for whom oppositions themselves have an attraction, just as triads certainly do for some others. If so, the series of opposites set up by the Pythagoreans may have had this motivation. Since, however, they reduced the two sets to two fundamental principles, the Limit and the Unlimited, they may have been forced by their mathematical discoveries to acknowledge a difference that blocked the way to monism. Whatever the correct interpretation in their case, it is plain that no philosopher would in advance adopt dualism as an ideal at which to aim, in creating his world picture.

What in fact drew attention to dualism as a type of theory was theology, where doctrines like Manichaeism, with its two ultimate principles of good and evil, or darkness and light, are found. Those who put forward such doctrines were labeled "dualists" by Thomas Hyde, writing in Latin about 1700. Later the term found its way into philosophy in various languages.


If there is more than one kind of existent, why not any number instead of just two? The unsuccessful would-be monist may, through thinking in this way, lapse into pluralism. Others, like William James, may find they have a temperamental objection to monism, with its emphasis on the totality and its exclusion of individuality and quirkiness. Yet others may from the start see the world as having some kind of disconnectedness as an essential feature, without which motion, change, and free will, for example, would be impossible. The rejection of any form of monism of course entails adopting the corresponding pluralist viewpoint. There may, however, be different types of rejection. Pluralism may arise from the rejection of the metaphysical conception of the "block universe" or of the logical doctrine that all true statements are, in the last analysis, logically necessary. For if there are some truths of a merely contingent nature, the doctrine of internal relations, that all relations are grounded in the natures of the related terms, must be false, and this doctrine is fundamental to the idealist versions of monism. The case of Leibniz, who is often taken as a standard pluralist, does not illustrate this point, but an instance of this sort of conversion to pluralism is afforded by Russell, who writes of his early position, "I came to disbelieve Bradley's arguments against relations, and to distrust the logical bases of monism" (The Philosophy of Bertrand Russell, edited by P. A. Schilpp, Evanston, IL, 1944, pp. 1112). Russell later adopted a full-blown pluralism associated with logic: For instance, "When I say that my logic is atomistic, I mean that I share the common-sense belief that there are many separate things" ("The Philosophy of Logical Atomism," 1918; reprinted in his Logic and Knowledge, New York, 1956, p. 178). Though this phase of Russell's philosophy is usually known as logical atomism, he also described it himself as "absolute pluralism." Even after abandoning logical atomism, Russell remained an enthusiastic pluralist; in 1931 he wrote of the proposition that the world is a unity, "the most fundamental of my intellectual beliefs is that this is rubbish. I think the universe is all spots and jumps, without unity, without continuity, without coherence or orderliness or any of the other properties that governesses love" (The Scientific Outlook, New York, 1931, p. 98).

See also Bradley, Francis Herbert; Categories; Descartes, René; Dualism in the Philosophy of Mind; Hegel, Georg Wilhelm Friedrich; James, William; Kant, Immanuel; Leibniz, Gottfried Wilhelm; Mani and Manichaeism; Mind-Body Problem; Parmenides of Elea; Plato; Pluralism; Russell, Bertrand Arthur William; Ryle, Gilbert; Schelling, Friedrich Wilhelm Joseph von; Smart, John Jamieson Carswell; Spinoza, Benedict (Baruch) de; Wolff, Christian.


Helpful general discussions of monism, dualism, and pluralism are rather few in number. The only good general account of all three is A. M. Quinton, "Pluralism and Monism," in the Encyclopaedia Britannica. The best sources, though more difficult to use, are the actual works of the philosophers mentioned as proponents of the various doctrines.


On monism see the works of philosophers named in the text, such as Parmenides, Spinoza, and Bradley. A useful discussion is C. E. M. Joad, "Monism in the Light of Recent Developments in Philosophy," in PAS 17 (19161917): 95116. Now somewhat antiquated is A. Worsley, Concepts of Monism (London, 1907). A typical short account from the heyday of monism in British philosophy is A. E. Taylor, Elements of Metaphysics (London: Methuen, 1903), Chs. 23. Compare J. A. Smith, "The Issue between Monism and Pluralism," in PAS 26 (19251926): 124. See also Marvin Farber, "Types of Unity and the Problem of Monism," in Philosophy and Phenomenological Research 4 (19431944): 3758, and postscript, ibid., 6 (19451946): 547583; Raphael Demos, "Types of Unity According to Plato and Aristotle," ibid., 534545; Abraham Edel, "Monism and Pluralism," in Journal of Philosophy 31 (21) (October 1934): 561571; and Jonathan Bennett, "A Note on Descartes and Spinoza," in Philosophical Review 74 (3) (July 1965): 379380. Such nineteenth-century works as Ernst Haeckel, Der Monismus als Band zwischen Religion und Wissenschaft (Bonn: E. Strauss, 1893; translated by J. Gilchrist as Monism as Connecting Religion and Science, London: A. and C. Black, 1895), are not now of much philosophical interest, for they are not about monism in general but are presentations of an outdated type of materialism.


On dualism see the main works of Descartes. The difficulties of the dualist position in general are well brought out by John Passmore in his Philosophical Reasoning (London: Duckworth, 1961), Ch. 3. See also Simone Pétrement, Le dualisme chez Platon, les gnostiques, et les manichéens (Paris: Presses Universitaires de France, 1947).


The most readable book on pluralism and other theories is William James's A Pluralistic Universe (London: Longman, 1909). For further reading, there is James Ward, The Realm of Ends, or Pluralism and Theism (Cambridge, U.K.: Cambridge University Press, 1911). A dry but clear account is to be found in C. D. Broad, The Mind and Its Place in Nature (London: Kegan Paul, 1925), introduction. More difficult and technical but classic is G. E. Moore, "External and Internal Relations," in PAS 20 (19191920): 4062, reprinted in his Philosophical Studies (New York: Harcourt Brace, 1922). Compare Bertrand Russell, "The Nature of Truth," in Mind 15 (1906): 528533, reprinted as "The Monistic Theory of Truth," in Russell's Philosophical Essays (London: Allen and Unwin, 1910). See also J. H. Muirhead, F. C. S. Schiller, and A. E. Taylor, "Why Pluralism?," in PAS 9 (19081909): 183225; and P. Laner, Pluralismus oder Monismus (1905).

Roland Hall (1967)