MONISM. — From μόνος "unique," it is, in the proper sense, any system that considers the multiplicity of things to be apparent, resolving it into a fundamental and absolute unity. The term is due to Chr. Wolff: "Monistae dicuntur philosophi qui unum tantum modo substantiae genus admittunt" (Psych. ration., § 32). The meaning of monism is therefore, first and foremost, metaphysical, as it presents itself as a system of interpreting reality in its constitutive and resolutive principle, both in terms of being and operation.
At this level, monism upholds the absolute unity of being and substance, opposing any dualism (v.) and pluralism (v.) that admit a final constitutive heterogeneity in the various orders, moments, or values of the real. It therefore affirms the fundamental identity of matter and spirit (v.), body and soul (v.), being and operation, substance (v.) and its determinations, nature and consciousness (v.), physical laws and biological laws, sense and intellect (v.), object and subject (v.), world and God (v.). The various qualifications of monism depend on the different conceptions of reality that are posited as the foundation and resolution of the whole. For materialistic monism, the only absolute reality is matter (v.) as the principle of force, energy, life, spirit, thought, and consciousness. Another expression of materialistic monism is energism (W. Ostwald, Die Energien, Leipzig 1908; V. DYNAMISM), inasmuch as it also resolves all reality and phenomena into a materialistic principle, essentially considered as force. Naturalism (v.) and evolutionism, in their most rigorous sense, are further determinations of materialistic monism, developed from the predominantly dynamic viewpoint of material reality itself. Opposed to materialistic monism (but ultimately only on the systematic and phenomenal level, for the final resolution, common to both, of being and experience into absolute unity) is spiritualistic monism. This is twofold: voluntaristic (or teleological) if it understands the fundamental reality as tendency or Will; intellectualistic (logical) if the only absolute reality is understood as Spirit, Thought, Intellectualism, Self-consciousness, Self-existence. In panlogism (v.), spiritualistic monism can be conceived with a static meaning (resolution of all things into an immutable spiritual Principle), or emanationistic (the world posited through a process of derivation from the spiritual principle), or dialectical (reality as the very immanent process of spirit). Between materialistic monism and spiritualistic monism may be placed (though here too the difference is only systematic) synthetic monism (or identity monism), which understands the one fundamental reality as an original indeterminate synthesis of matter and spirit; and ontological monism, which disregards any original determination of reality, affirming absolute Unity on the transcendent plane of pure being. Monistic are the absolute forms of immanentism (v.) and pantheism (v.), which differs from monism in general in that it recognizes divine value and significance in all reality.
The further particular meanings of the term "monism" are mostly, though not necessarily, derivations and applications of its fundamental metaphysical meaning. Physical monism upholds the specific identity of substance within the physical world: physical monism is therefore any system that affirms the original unity of matter, attributing the specific diversities of bodies to mere accidental determinations (quantitative variations and aggregations: atomism, mechanism, v.). To physical monism belong some forms of hylozoism (v.), which conceives the world as a single organism informed by a living principle, whether naturalistic or divine. Anthropological-psychological monism is the actualistic theory (v. ACTUALISM) that maintains the identity of physiological phenomena and conscious phenomena as expressions or parallel series of one and the same fundamental reality. It is also called the "identity theory" and rejects the conception of the soul as a substance distinct from the body. Epistemological monism denies any essential difference between sensitive knowledge and intellectual knowledge: in this sense, empiricism (v.) and nominalism (v.) are monistic. In a broader sense, epistemological monism is the affirmation of the absolute identity between subject and object. Ethical monism is any conception that upholds the autonomy (v.) of morality, whether in a spiritualistic sense (morality as a universal value immanent to reason) or in a materialistic-hedonistic sense (morality as a pure derivation and transformation of egoistic, utilitarian, altruistic tendencies of human nature, and as a product of feeling, custom, and tradition). Social monism (opposed both to the atomistic and to the personalistic conception of society) posits the State as the supreme value over against individuals and thus as the unique measure of law, source and term of every right and duty (v. INDIVIDUALISM; PERSONALISM; SOCIETY). Historical monism is finally the conception of history (v.) as a necessary process of a single absolute reality, excluding any real indetermination or self-determination of human freedom.
Monism found expression in Indian pantheism (Upanishads), in which Brahma is understood as the supreme impersonal reality of which the world is but a manifestation. Monists are the first Greek philosophers who attempted to resolve nature into a single principle (ἀρχή φύσεως): Thales, Anaximenes, Anaximander ("he said that the infinity of nature is that from which all things are generated": F. G. A. Mullach, Fragm. philosophorum graec., I, p. 237), Heraclitus (op. cit., p. 312 b; cf. Aristotle, Met., I, 3). Monistic, as far as can be gathered from the fragments, is the doctrine of the Eleatics. Xenophanes identifies God, the One and All (ἐν καὶ πᾶν), with the world (theological monism); everything therefore has its source in the identical and "resolves into a single nature" (μὰν εἰς φύσιν: Sextus Empiricus, Pyrrh. Hypot., I, 224; cf. Plato, Soph., 242 d). For Parmenides, being is ungenerated, immortal, complete, unitary, immobile, eternal (οὐλόν, μουνογενές τε καὶ ἀγενὲς ἀώδυτον: Mullach, op. cit., p. 120, 60; cf. Plato, Soph., 244 e). There is no origin, multiplicity, or becoming in being, and there is identity between being and thinking: τὸ γὰρ αὐτὸ νοεῖν ἐστὶν τε καὶ εἶναι (Mullach, op. cit., p. 118, 40). Parmenides' ontological monism resolves into materialism, through the identification of being with corporeality (τὸ πλῆρες).
Materialist monists include the atomists (Democritus, Leucippus: cf. ARISTOTLE, *Phys.*, I, 4, 5; *Met.*, I, 8; EPICURUS, Lucretius). The Stoics, dualists in ethics (opposition between virtue and passion, sense and reason), defend a metaphysical monism: the λόγος (reason) is the universal reality that vivifies and unifies the universe: «Dei vero substantiam Zeno quidem ait mundum totum atque coelum» (DIOGENES LAERTIUS, VII, 1, 148). Plotinus also tends toward spiritualistic monism insofar as matter itself seems to be conceived as an emanation of the One.
Expressions of a panentheistic monism are found in John Scotus Eriugena (v.), even if in the end he seems to free himself from a true and proper monism, and in David of Dinant. A form of anthropological monism is offered by the doctrine of Averroes (v.) on the unity of the intellect.
Renaissance philosophy, with Neoplatonic and Stoic derivations and in dependence on the new scientific conception of the universe (v.), returns to the immaculate “divine force” in nature. BRUGNATO (v.), God is the formal cause and internal principle of the world, which from its inmost being expresses aspects and forms; and it is the only life of God that manifests itself in all worlds (*On the Infinite, the Universe and the Worlds*, II, ed. G. Gentile, *Opere italiane*, I, 2nd ed., Bari 1925, pp. 178 ff.). Similarly, Paracelsus, Valentin Weigel, Giulio Cesare Vanini, and Jakob Böhme (*Morgenröte*, chaps. 2–3).
In modern philosophy, BERGER, ELIE (v.) presents a form of anthropological monism: man is only spirit; the body (and matter in general) is pure representation. Metaphysical monism Spinoza (v.), for whom thought and extension are pure manifestations of the single divine substance: «substantia cogitans et substantia extensa una eademque est substantia» (*Ethics*, Part 2, Proposition 6, scholium; ed. G. Gentile, 2nd ed., Bari 1933, p. 53; cf. pp. 4, 6). Materialistic monism is defended by Claude-Adrien Helvétius, Denis Diderot (*Pensées sur l'interprétation de la nature*, London 1744), Julien Offray de La Mettrie (*L’homme machine*, Paris 1748), Paul-Henri Thiry, Baron d’Holbach (*Système de la nature*, London [Amsterdam or Leiden] 1770), Pierre-Jean-Georges Cabanis (*Rapports du physique et du moral de l'homme*, Paris 1802), Jakob Moleschott (*Der Kreislauf des Lebens*, Mainz 1832), Ludwig Büchner (*Kraft und Stoff*, Frankfurt 1855), Carl Vogt, Heinrich Czolbe (*Köhlerglaube und Wissenschaft*, Giessen 1854; *Vorlesungen über den Menschen...*, ibid. 1863); by Darwinian evolutionism, Haeckel (v.). For Haeckel (whose system can be considered a synthesis of Spinoza, Bruno, and Darwin), the substance of the world is at once God and nature and has as its attributes matter and force. Consequently, any spiritual order that is posited as distinct from and transcendent to the order and finality of the body is excluded (*The Riddle of the Universe*, chaps. 18–19). Similarly to Haeckel, Hugo Münsterberg (*Grundzüge der Psychologie*, Leipzig 1900) and Theodor Ziehen (*Gehirn und Seelenleben*, ibid. 1902).
Monistic is post-Kantian idealism. For Schelling (v.), reality is the inner process of the absolute as the original principle and infinite tendency (influenced by Bruno and Spinoza), in whose identity every distinction is resolved. For Hegel (v.), multiplicity is a pure dialectical moment in the becoming of the single and supreme reality, the Idea: «only the absolute Idea is being, life that does not pass away, truth that is concise in itself, and it is all truth» (*Science of Logic*, Italian trans. by A. Moni, III, Bari 1925, p. 305). Monistic is the conception of Eduard von Hartmann (v.), for whom the One, while expressing itself through its dynamic functions in a multiplicity of individuals, remains immanent to them; SCHOPENHAUER, ARTHUR (v.), for whom the world and man and all their phenomenal manifestations are expressions of the single fundamental reality, the Will (*Wille zur Leben*). Similarly, Fouillée (v.), who admits the fundamental identity between nature and thought insofar as the will, dispersed in the world and in eternal expansion, reflects back upon itself, concentrates, and becomes conscious in man.
Monistic is the dialectical materialism of Ludwig Feuerbach (*Gottheit, Freiheit u. Unsterblichkeit*, Leipzig 1886) and Marxism, to which is proper the affirmation of the exclusive naturalistic-economic significance of the world of the spirit. Psycho-physical anthropological monism is defended by Gustav Fechner (*Elemente der Psychophysik*, Leipzig 1860; the “physical” is the external aspect, the “psychic” the internal aspect of a single reality), Friedrich Paulsen, Wilhelm Wundt, and also by Hippolyte Taine, Alexander Bain, Friedrich Jodl, Hermann Ebbinghaus, Herbert Spencer, who consider the “physical” and the “psychic” to be manifestations of a further reality (Neo-Spinozism). For Spencer, consciousness and matter are «pure symbols of a Power that is forever and absolutely unknown to us» (*Principles of Psychology*, § 63).
Monistic is Gentile’s actualism: «the finite thing is always the very reality of God» and the world «an eternal theogony that is fulfilled in the inmost of our being» (*Teoria generale dello spirito come atto puro*, 5th ed., Florence 1938, p. 265). Existentialism (v.) in its atheistic and agnostic forms is also fundamentally inspired by monism.
In Germany, the Monistenbund (founded in Jena in 1906; before the First World War it had about 7,000 members in 45 sections; cf. *Monistenbund*, in *LThK*, VII, cols. 281–82) enjoyed wide diffusion in the first decades of the 20th century. The purpose of the Monistenbund, openly anti-Christian and anti-Catholic, was to spread a naturalistic conception, excluding from science and philosophy any supernatural factor. Less radical was the journal *The Monist* (founded by Paul Carus, Chicago, January 1891), which aimed to defend the unity and harmony of all truths and thus also the reconciliation between science and faith. Nevertheless, it too embraced the fundamental monist idea of an inseparable unity of the whole, and in science the monistic conception of Haeckel.
Monism, considered in its fundamental metaphysical expression, is radically irreconcilable with Christianity. It involves, in fact, the negation of the transcendence and personality of God and thus, besides obviously opposing the very possibility of a supernatural order, it suppresses the only valid foundation of religion, of a universal ethics, and of an authentic spiritual conception of life. Whether understood in a materialistic or idealistic sense, monism is unable to preserve the Christian concepts of freedom, responsibility, obligation, conscience, and sin (v. the respective entries). From a philosophical point of view, it must be observed that the irreducible multiplicity of personal consciences, of which the whole human world is a clear manifestation, finds no real explanation in monism. Even in the order of lower nature, the plurality of structures, living and non-living, manifests on the empirical-phenomenal plane a specificity so profound that it cannot have its adequate reason except in a diversification that reaches back to the very ontological level of being. «It is impossible to resolve all things into unity» (ἀδύνατον φαίνεται τὰ ὄντα ἐν εἶναι: ARISTOTLE, *Phys.*, I, 3, 186 a 4; cf. *De generatione et corruptione*, I, 1; PLATO, *Sophist*, 244 b).
It must further be noted that monism, by closing the becoming of reality within itself, is ultimately forced into a radical irrationalism (v.) that makes the act (v.) derive from potency, the determined
from the indeterminate and therefore being from non-being. Conclusions that Christian thought is able to avoid by positing the ontological distinction between absolute and relative, being per se and participated being. This does not negate the positive thrust of monism, namely the exigency of explaining and reducing all reality to a single Principle, in opposition to the extreme expressions of dualism, which is fully preserved in Christian thought. Only here the unity of being is achieved not through identity, but on the basis of the relationship of causality, the sole dialectical moment that, by grounding the derivation of the relative from the absolute, simultaneously opposes its resolution into the absolute itself and guarantees on the plane of being its own consistency. V. CONOSCENZA; DIO; ENTE-ESSERE; PANTEISMO; SOSTANZA.