Monism (from the Greek monos, "one", "alone", "unique") is a philosophical term which, in its various meanings, is opposed to Dualism or Pluralism. Wherever pluralistic philosophy distinguishes a multiplicity of things, Monism denies that the manifoldness is real, and holds that the apparently many are phases, or phenomena, of a one. Wherever dualistic philosophy distinguishes between body and soul, matter and spirit, object and subject, matter and force, the system which denies such a distinction, reduces one term of the antithesis to the other, or merges both in a higher unity, is called Monism.
I. IN METAPHYSICS.—The ancient Hindu philosophers stated as a fundamental truth that the world of our sense-experience is all illusion (maya), that change, plurality, and causation are not real, that there is but one reality, God. This is metaphysical Monism of the idealistic-spiritual type, tending towards mysticism. Among the early Greek philosophers, the Eleatics, starting, like the Hindus, with the conviction that sense-knowledge is untrustworthy, and reason alone reliable, reached the conclusion that change, plurality, and origination do not really exist, that Being is one, immutable, and eternal. They did not explicitly identify the one reality with God, and were not, so far as we know, inclined to mysticism. Their Monism, therefore, may be said to be of the purely idealistic type. These two forms of metaphysical Monism recur frequently in the history of philosophy; for instance, the idealistic-spiritual type in neo-Platonism and in Spinoza's metaphysics, and the purely idealistic type in the rational absolutism of Hegel. Besides idealistic Monism there is Monism of the materialistic type, which proclaims that there is but one reality, namely, matter, whether matter be an agglomerate of atoms, a primitive, world-forming substance (see Ionian School of Philosophy), or the so-called cosmic nebula out of which the world evolved. There is another form of metaphysical Monism, represented m these days by Haeckel and his followers, which, though materialistic in its scope and tendency, professes to transcend the point of view of materialistic Monism and unite both matter and mind in a higher something. The weak point of all metaphysical Monism is its inability to explain how, if there is but one reality, and everything else is only apparent, there can be any real changes in the world, or real relations among things. This difficulty is met in dualistic systems of philosophy by the doctrine of matter and form, or potency and actuality, which are the ultimate realities in the metaphysical order. Pluralism rejects the solution offered by scholastic dualism and strives, with but little success, to oppose to Monism its own theory of synechism or panpsychism (see Pragmatism). The chief objection to materialistic Monism is that it stops short of the point where the real problem of metaphysics begins.
II. IN THEOLOGY.—The term Monism is not much used in theology because of the confusion to which its use would lead. Polytheism, the doctrine that there are many Gods, has for its opposite Monotheism, the doctrine that there is but one God. If the term Monism is employed in place of Monotheism, it may, of course, mean Theism, which is a monotheistic doctrine, or it may mean Pantheism, which is opposed to theism. In this sense of the term, as a synonym for Pantheism, Monism maintains that there is no real distinction between God and the universe. Either God is indwelling in the universe as a part of it, not distinct from it (pantheistic Immanentism), or the universe does not exist at all as a reality (Acosmism), but only as a manifestation or phenomenon of God. These views are vigorously combated by Theism, not only on considerations of logic and philosophy, but also on considerations of human life and conduct. For the ethical implications of pantheism are as detrimental to it as its shortcomings from the point of view of consistency and reasonableness. Theism does not deny that God is indwelling in the universe; but it does deny that He is comprised in the universe. Theism does not deny that the universe is a manifestation of God; but it does deny that the universe has no reality of its own. Theism is, therefore, dualistic: it holds that God is a reality distinct from the universe and independent of it, and that the universe is a reality distinct from God, though not independent of Him. From another point of view, theism is monistic; it maintains that there is but One Supreme Reality and that all other reality is derived from Him. Monism is not then an adequate equivalent of the term Theism.
III. IN PSYCHOLOGY.—The central problem of rational psychology is the question of the relation between soul and body. Scholastic dualism, following Aristotle, maintains that man is one substance, composed of body and soul, which are respectively matter and form. The soul is the principle of life, energy, and perfection; the body is the principle of decay, potentiality, and imperfection. These two are not complete substances: their union is not accidental, as Plato thought, but substantial. They are, of course, really distinct, and even separable; yet they act on each other and react. The soul, even in its highest functions, needs the cooperation, at least extrinsic, of the body, and the body in all its vital functions is energized by the soul as the radical principle of those functions. They are not so much two in one as two forming one compound. In popular imagination this dualism may be exaggerated; in the mind of the extreme ascetic it sometimes is exaggerated to the point of placing a too sharp contrast between "the flesh" and "the spirit", "the beast" and "the angel", in us.
Psychological Monism tends to obliterate all distinction between body and soul. This it does in one of three ways. (A) Monism of the materialistic type reduces the soul to matter or material conditions, and thus, in effect, denies that there is any distinction between soul and body. The Stoics described the soul as a part of the material world-substance; the Epicureans held that it is a compound of material atoms; modern Materialism knows no substantial soul except the nervous system; Cabanis, for instance, proclaims his materialism in the well-known crude formula: "The brain digests impressions, and organically secretes thought." Psychological materialism, as metaphysical materialism, closes its eyes to those phenomena of the soul which it cannot explain, or even denies that such phenomena exist. (B) Monism of the idealistic type takes an entirely opposite course. It reduces the body to mind or mental conditions. Some of the neo-Platonists held that all matter is non-existent, that our body is, therefore, an error on the part of our minds, and that the soul alone is the personality.
John Scotus Eriugena, influenced by the neo-Platonists, held the body to be a resultant from incorporeal qualities which the soul, by thinking them and synthesizing them, creates into a body for itself. In modern times, Berkeley included the human body in his general denial of the reality of matter, and maintained that there are no substances except the soul and God. The grounds for this belief are epistemological. Psychological Monism runs counter to common sense and experience. Historically, it is a reaction against materialism. To refute materialism it is not necessary to deny that the body is a reality. The unreflecting dualism of common sense and the scientific dualism which the Scholastics built on the facts of experience steer a safe and consistent course between the hasty generalization of the Materialist, who sees nothing but body, and the bold paradox of the Idealist, who recognizes no reality except mind.
(C) A third kind of psychological Monism goes by the name of psychophysical parallelism. It maintains two principles, the one negative and the other affirmative. First, it denies categorically that there is, or can be, any direct causal influence of the soul on the body or of the body on the soul: our thoughts cannot produce the movements of our muscles, neither can the action of light on the retina produce in us the "thought" of a color. Secondly, it affirms in some shape or form that both the body and the soul are phases of something else, that this something evolves its activities along two parallel lines, the physical and the psychical, so that the thought, for instance, of moving my hand is synchronous with the motion of my hand, without one in any way influencing the other. This is the doctrine of Occasionalists who, like Malebranche, (q.v.), maintain that the union of the soul and body "consists in a mutual and natural correspondence of the thoughts of the soul with the processes of the brain, and of the emotions of the soul with the movements of the animal spirits" (Rech. de la Write, II, v). It is the doctrine of Spinoza, whose metaphysical Monism compelled him to hold that body and soul are merely aspects of the one substance, God, under the attributes extension and thought, but that they unfold their modes of activity in a manner preordained to correspondence (Eth., II, ii, schol.). Leibniz meets the difficulty in his own characteristic way by teaching that all monads are partly material and partly immaterial, and that among all monads and their activities there exists a preestablished harmony (see System of Leibniz; Monad). In the so-called Identitatsphilosophie of some German Transcendentalists, such as Schelling, reality is mind in so far as it is active, and matter in so far as it is passive; mind and matter are, therefore, two harmonious, but independent, series of phases of reality. Fechner's view is similar: he holds that the reality pervading the whole universe is at once physical and psychical, that, the physical is the "exterior" and the psychical the "interior", or "inner", side of reality, and that the body and soul in man are but one instance of a parellelism which prevails everywhere in nature. Paulsen ("Introd. to Phil.", tr. Thilly, 87 sqq.) holds that "two propositions are contained in the theory of parallelism: (I) Physical processes are never effects of psychical processes; (2) Psychical processes are never effects of physical processes." He adopts Fechner's pan-psychism, maintaining that "everything corporeal points to something else, an inner, intelligible element, a being for itself, which is akin to what we experience within ourselves". Both the corporeal and the "inner" are parts of the universal system, which is the body of God, and, though they do not interact, they act in such a way that harmony results.
Herbert Spencer uses the word parallelism in a slightly different sense: the separate impressions of the senses and the stream of inner conscious states must be adjusted by the activity of the mind, if the two series are to be of any use to the developing or evolving animal or man; that is, there must be a parallelism between a certain physical evolution and the correlative psychical evolution" (Principles of Psych., n. 179), while both mind and matter are mere "symbols of some form of Power absolutely and forever unknown to us" (op. cit., n. 63). This idea finds favor among the evolutionists generally, and has one distinct advantage: it obviates the necessity of explaining many phenomena of mind which could not be accounted for by the principles of materialistic evolution. Thus, under the name "double-aspect theory" it is adopted by Clifford, Bain, Lewes, and Huxley. Among empirical psychologists parallelism has been found satisfactory as a "working hypothesis". Experience, it is maintained, tells us nothing of a substantial soul that acts on the body and is acted upon. It does tell us, however, that psychical states are apparently conditioned by bodily states, and that states of body apparently influence states of mind. For the purposes of science, conclude the empiricists, it is enough to maintain as an empirical formula that the two streams of activity are, so to speak, parallel, though never confluent. There is no need to ground the formula on any universal metaphysical theory, such as the pan-psychism of Fechner and Paulsen. It is enough that, as Wundt points out, the facts of experience establish a correspondence between physical and psychical, while the dissimilarity of the physical and the psychical precludes the possibility of one being the cause of the other. To all these parallelistic explanations of the relations between soul and body the Scholastic dualists take exception. First, the scholastics call attention to the verdict of experience. Up to a certain point, the facts of experience are capable of a parallelistic, as well as of a dualistic, explanation. But when we come to consider the unity of consciousness, which is a fact of experience, we find that the theory of parallelism breaks down, and the only explanation that holds is that of dualists, who maintain the substantiality of the soul. Secondly, if the parallelistic theory be true, what, ask the Scholastic dualists, becomes of the freedom of the will and moral responsibility? If our mental and bodily states are not to be referred to an immediate personal subject, but are considered phases or aspects of a universal substance, a cosmic soul, mind-stuff, or unknown "form of Power", it is not easy to see in what sense the will can be free, and man be held responsible for his mental or bodily acts.
In a minor sense the word monism is sometimes used in psychology to designate the doctrine that there is no real distinction between the soul and its faculties, Psychological dualism holds that soul and body are distinct, though incomplete, substances. But how about the soul itself? Plato's doctrine that it has three parts has had very little following in philosophy. Aristotle distinguished between the substance of the soul and its powers (dunameis), or faculties, and bequeathed to the Schoolmen the problem whether these faculties are really, or only notionally, distinct from the soul itself. Those who favor the real distinction are sometimes called pluralists in psychology, and their opponents, who say that the distinction is nominal or, at most, notional, are sometimes called psychological Monists. The question is decided by inferences from the facts of consciousness. Those who hold real distinction of function argue that this is sufficient ground for a real distinction of faculties.
IV. IN EPISTEMOLOGY, as in psychology, Monism is used in various senses to signify, in a general way, the antithesis of dualism. The Dualist in epistemology agrees with the ordinary observer, who distinguishes both in theory and in practice between "things" and "thoughts". Common sense, or unreflecting consciousness, takes things generally to be what they seem. It acts on the conviction that the internal world of our thoughts corresponds with the external world of reality. The philosophical dualist questions the extent and accuracy of that correspondence; he learns from psychology that many instances of so-called immediate perception have in them a large share of interpretation, and are, in so far, referable to the activity of the mind. Nevertheless, he sees no reason to quarrel with the general verdict of common sense that there is a world of reality outside us, as well as a world of representation within us, and that the latter corresponds in a measure to the former. He distinguishes, therefore, between subject and object, between self and not-self, and holds that the external world exists. The Monist in one way or another eliminates the objective from the field of reality, obliterates the distinction between self and not-self, and denies that the external world is real. Sometimes he takes the ground of idealism, maintaining that thoughts are things, that the only reality is perception, or rather, that a thing is real only in the sense that it is perceived, esse est percipi. He scorn-fully rejects the view of naive realism, refers with contempt to the copy-theory (the view that our thoughts represent things) and is rather proud of the fact that he is in conflict with common sense. Sometimes he is a solipsist, holding that self alone exists, that the existence of not, self is an illusion, and that the belief in the existence of other minds than our own is a vulgar error. Sometimes, finally, he is an acosmist: he denies that the external world exists except in so far as it is thought to exist: or he affirms that we create our own external world out of our own thoughts.
However, the classical form of epistemological Monism at the present time is known as Absolutism. Its fundamental tenet is metaphysical monism of the purely idealistic type. It holds that both subject and object are merely phases of an abstract, unlimited, impersonal consciousness called the Absolute; that neither things nor thoughts have any reality apart from the Absolute. It teaches that the universe is a rational and systematic whole, consisting of an intellectual "ground" and multiform "appearances" of that ground, one appearance being what the Realist calls things, and another what the Realist calls thoughts. This is the doctrine of the Hegelians, from Hegel himself down to his latest representatives, Bradley and McTaggart. All these forms of epistemological Monism—namely, idealism, solipsism, acosmism, and absolutism—have, of course, metaphysical bearings, and sometimes rest on metaphysical foundations. Nevertheless, historically speaking, they are traceable to a psychological assumption which is, and always will be, the dividing line between Dualism and Monism in epistemology. The Dualists, in their analysis of the act of knowing, call attention to the fact that in every process of perception the object is immediately given. It seems like emphasizing the obvious to say so, yet it is precisely on this point that the whole question turns. What I perceive is not a sensation of whiteness but a white object. What I taste is not the sensation of sweetness but a sweet substance. No matter how much the activity of the mind may elaborate, synthesize, or reconstruct the data of sense-perception, the objective reference cannot be the result of any such subjective activity; for it is given originally in consciousness. On the contrary, the Monist starts with the idealistic assumption that what we perceive is the sensation. Whatever objective reference the sensation has in our consciousness is conferred on it by the activity of the mind. The objective is, therefore, reducible to the subjective; things are thoughts; we make our world. In the dualist's analysis there is immediate, presentative contact in consciousness between the subject and the object. In the Monist's account of the matter there is a chasm between subject and object which must be bridged over somehow. The problem of Dualism or Monism in epistemology depends, therefore, for solution on the question whether perception is presentative or representative; and the dualist, who holds the presentative theory, seems to have on his side the verdict of introspective psychology as well as the approval of common sense.
In recent Pragmatist contributions to epistemology there is presented a different view of epistemological Monism from that given in the preceeding paragraphs, and a solution is offered which differs entirely from that of traditional dualism. In William James's works, for instance, Monism is described as that species of Absolutism which "thinks that the all-form or collective-unit form is the only form that is rational", while opposed to it is Pluralism, that is, the doctrine that "the each-form is an eternal form of reality no less than it is the form of temporal appearance" (A Pluralistic Universe, 324 sqq.). The multitude of "each-forms" constitute, not a chaos, but a cosmos, because they are "inextricably interfused" into a system. The unity, however, which exists among the "each-forms" of reality is not an integral unity nor an articulate or organic, much less a logical, unity. It is a unity "of the strung-along type, the type of continuity, contiguity, or concatenation" (op. cit., 325). Into this unfinished universe, into this stream of successive experiences, the subject steps at a certain moment. By a process which belongs, not to logic, but to life, which exceeds logic, he connects up these experiences into a concatenated series. In other words, he strings the single beads on a string, not of thought, but of the practical needs and purposes of life. Thus the subject makes his own world, and, really, we are not any better off than if we accepted the verdict of the intellectualistic Idealist. We have merely put the practical reason in place of the theoretical: so far as the value of knowledge is concerned the antithesis between Monism and Pluralism is more apparent than real, and the latter is as far from the saneness of realistic Dualism as the former. It is true that the Pluralist admits, in a sense, the existence of the external world; but so also does the Absolutist. The trouble is that neither admits it in a sense which would save the distinction between subject and object. For the Pluralist as well as the Monist is entangled in the web of subjective Idealism as soon as he favors the doctrine that perception is representative, not presentative.
V. IN COSMOLOGY, the central question is the origin of the universe. The early Ionian philosophers assigned, as the cause or principle (arche is the Aristotelian word) of the universe, a substance which is at once the material out of which the universe is made and the force by which it was made. As Aristotle says, they failed to distinguish between the material cause and the efficient cause. They were, therefore, dynamists and hylozoists. That is, they held matter to be of its nature active, and endowed with life. Without the aid of any extrinsic force, they said, the original substance, by a process of thickening and thinning, or by quenching and kindling, or in some other immanent way, gave rise to the universe as we now see it. This primitive cosmothetic Monism gradually gave way to a dualistic conception of the origin of the world. Tentatively at first, and then more decisively, the later Ionians introduced the notion of a primitive force, distinct from matter, which fashioned the universe out of the primordial substance. Anaxagoras it was, who, by clearly defining this force and describing it as mind (nous), earned the encomium of being the "first of the ancient philosophers who spoke sense". Dualism, thus introduced, withstood the onslaughts of materialistic Atomism and Epicureanism, pantheistic Stoicism and emanationistic neo-Platonism. It was developed by Socrates, Plato, and Aristotle, who brought to their description of the world-forming process a higher notion of cosmothetic mind than the pre-Socratic philosophers possessed. It was left for the Christian philosophers of Alexandria and their successors, the Scholastics of medieval times, to elaborate the doctrine of creation ex nihilo, and thus bring out more clearly the role played by the Divine Power and Will in the formation of the universe. The order, harmony, and purposiveness evident everywhere in nature are cited by the creationists as evidence to show that mind must have presided at the origination of things. Furthermore, the question of dynamism or mechanism hinges on the problem of the nature of matter. This phase of the question has been developed especially in post-Cartesian philosophy, some maintaining that matter is essentially inert and must, therefore, have acquired force and activity from without, while others as stoutly maintain that matter is by nature active and, consequently, may have developed its own force from within. Evolution of the thoroughgoing type takes the latter view. It holds that in the primitive cosmic matter was contained "the power and potency" of all life and movement, in such a way that no external agent was required in order to bring it to actual existence. Here, as in the question of Theism, Christian philosophy is frankly dualistic, although it acknowledges that, since actuality antecedes potency by nature and, as a matter of fact, the world originated in time while God is eternal, there was, before creation, but One Reality.
VI. IN ETHICS, the word Monism is very little used. In some German works it is employed to designate the doctrine that the moral law is autonomous. Christian ethics is essentially heteronomic: it teaches that all law, even natural law, emanates from God. Kantian ethics and Evolutionistic ethics hold that the moral law is either self-imposed or emanates from the moral sense which is a product of the struggle for existence. In both the Kantian and the Evolutionistic systems there is only one source of the power of moral discrimination and approval. For this reason the word Monism is here used in its generic sense. In English philosophical literature, however, the word has no such signification. In accounting for the origin of evil, a problem which, though it belongs to metaphysics, has important bearings on ethical questions, some philosophers have adopted a Dualistic doctrine and explained that good and evil originate from two distinct principles, the one supremely good, the other completely and absolutely evil. This was the doctrine of the ancient Persians, from whom it was borrowed by Manes, the founder of the Manichean sect. Opposed to this is the Monistic view, that God is indeed the cause of all that is good in the universe, and that evil is not to be assigned to any supreme cause distinct from God. Whatever explanation be given of the existence of evil in the world, it is maintained that a supreme principle of evil is utterly impossible and even inconceivable.
VII. CONTEMPORARY MONISTIC MOVEMENTS AND SCHOOLS.—In current philosophical literature, when-ever no special qualification is added, Monism generally means the modified materialistic monism of Haeckel. Modern materialistic Monism in Germany begins with Feuerbach, a disciple of Hegel. Feuerbach was followed by Vogt and Moleschott. To these succeeded Haeckel, who combines Darwinian evolution with a materialistic interpretation of Spinoza and Bruno. Haeckel's works, both in the original and in English translations, have had a wide circulation their popularity being due rather to the superficial manner in which Haeckel disposes of the most serious questions of metaphysics than to any intrinsic excellence of content or method. Haeckel is honorary president of the Monistenbund (Society of Monists), founded at Jena in 1906, for the purpose of propagating the doctrines of Monism. The society is openly anti-Christian, and makes active warfare against the Catholic Church. Its publications, "Der Monist" (a continuation of the "Freie Glocken"—first number, 1906), "Blatter des deutschen Monistenbunds" (first number, July, 1906), and various pamphlets (Flugblatter des Monistenbunds), are intended to be a campaign against Christian education and the union of Church and State.
The group of writers in America who, under the editorship of Dr. Paul Carus, have been identified with the "Monist" (Chicago, monthly, first number, January, 1891) are not, apparently, actuated by the same animosity against Christianity. Nevertheless, they hold Haeckel's fundamental tenet that Monism as a system of philosophy transcends Christianity as a form of belief, and is the only rational synthesis of science and religion. "Religious progress no less than scientific progress", writes Carus, "is a process of growth as well as a cleansing from mythology.... Religion is the basis of ethics.... The ideal of religion is the same as that of science, it is a liberation of the mythological elements and its aim is to rest upon a concise but exhaustive statement of facts" (Monism, Its Scope and Import, 8, 9). This "concise but exhaustive statement of facts" is positive Monism, the doctrine, namely, that the whole of reality constitutes one inseparable and indivisible entirety. Monism is not the doctrine that one substance alone, whether it be mind or matter, exists: such a theory, says Dr. Carus, is best designated as Henism. True Monism "bears in mind that our words are abstracts representing parts or features of the One and All, and not separate existences" (op. cit., 7). This Monism is Positivistic, because its aim is "the systematisation of knowledge, that is, of a description of facts" (ibid.). "Radical free thought" is the motto of this school of Monism; at the same time, it disclaims all sympathy with destructive Atheism, Agnosticism, Materialism, and Negativism in general. Nevertheless, the untrained student of philosophy will be likely to be more profoundly influenced by the Monistic criticism of Christianity than by the constructive effort to put something in place of the errors referred to.
All Monism may be described as resulting from the tendency of the human mind to discover unitary concepts under which to subsume the manifold of experience. So long as we are content to take and preserve the world of our experience as we find it, with all its manifoldness, variety, and fragmentation, we are in the condition of primitive man, and little better than brute animals. As soon as we begin to reflect on the data of the senses, we are led by an instinct of our rational nature to reduce manifold effects to the unity of a causal concept. This we first do in the scientific plane. Afterwards, carrying the process to a higher plane, we try to unify these under philosophical categories, such as substance and accident, matter and force, body and mind, subject and object. The history of philosophy, however, shows with unmistakable clearness that there is a limit to this unifying process in philosophy. If Hegel were right, and the formula, "The rational alone is real", were true, then we should expect to be able to compass all reality with the mental powers which we possess. But, Christian philosophy holds, the real extends beyond the domain of the (finite) rational. Reality eludes our attempt to compress it within the categories which we frame for it. Consequently, Dualism is often the final answer in philosophy; and Monism, which is not content with the partial synthesis of Dualism, but aims at an ideal completeness, often results in failure. Dualism leaves room for faith, and hands over to faith many of the problems which philosophy cannot solve. Monism leaves no room for faith. The only mysticism that is compatible with it is rationalistic, and very different from that "vision" in which, for the Christian mystic, all the limitations, imperfections, and other shortcomings of our feeble efforts are removed by the light of faith.