Dualism in philosophy, is that system which explains the phenomena of the universe by assuming two primal principles instead of one (Monism). In theology, Dualism explains evil by assuming two original principles or beings, one good, the other evil. The doctrine of two primal causes, one good and the other evil, constantly warring with each other, lay at the foundation of the system of Zoroaster (q.v.). It was also developed later in Manicheism (q.v.); and among the Sclavonians, who, during the interval between their undisturbed faith in their national mythology and their conversion to Christianity, added to the worship of the good being that of a supremely evil one, viz. Czernebog (the Black God) (London Review, April 1855, page 11). It was in this Sclavonic soil that the Oriental dualism found a congenial home, and from it seems to have originated the dualism of the Cathari and other sects during the Middle Ages. SEE CATHARI.
Its root is always found in imperfect speculation on the relation of God to the world, and on the origin of evil. It is apt to spring up, also, in the practical sphere, from the sense of personal sin, which seeks relief in a transfer of guilt from the real self the man to something outside of him, e.g. to the physical side of his own nature, or to the general laws of nature.
1. Oriental Dualism. — The Chinese, at a very early period, adopted a dualistic philosophy and theology. The ordinary speech of their philosophers was dualistic, implying two primal essences, "one a power or cause, the other a more passive something on which that power or cause could operate. The former may be styled the ultimate immaterial principle of the universe (Le); the second, consisting of ethereal matter, is the ultimate material principle (Ke). The latter, again, is dual (yang and yin), viz. the paternal and maternal principles in nature. Man is the product of the marriage of the male and female principles in nature. Yang and yin, coexisting as the material ground in which the ultimate principle (Ke) takes effect, enter into the composition of rational as well as of irrational beings. In moral speculation, however, this dualism passed into a sort of pantheism" (Hardwick, Christ and other Masters, part 3, chapter 1).
The Persian Dualism. The Persian system, whether originated by Zoroaster, or, what is more likely modified by him from older doctrines, taught that there is "a supreme Being, all powerful and eternal, from whom have eternally proceeded, by his creative word (Honofer), two principles, Ormuzd and Ahriman; Ormuzd (Oromasdes) being pure and infinite Light, Wisdom, and Perfection, the Creator of every good thing; Ahriman the principle of darkness and evil, opposed to Ormuzd, either originally or in consequence of his fall. To this belief are attached fables respecting the conflicting efforts and creations of these two powers; on the universal dominion ultimately reserved for the good principle, and the return of Ahriman during four periods, each of which is to last three thousand years; on the good and the evil spirits (Amshaspands, Izeds, Ferfers, and Dives), and their differences of sex and rank; on the souls of men (Ferfers), which, created by Ormuzd before their union with the body, have their habitation in the heavens; and which ultimately, according as in this world they have served Ormuzd or Ahriman, pass after death into the dwellings of the blessed, or are precipitated into obscurity: finally, respecting the future resurrection of the bodies of the wicked after the victory of Ormuzd and the restoration of all things" (Tennemann, Manual Hist. of Philosophy, § 71; see also Hardwick, Christ and other Masters, part 3, chapter 3). The Oriental Dualism first sets the Hyle (ὕλη, matter) as an original principle over against the divinity. The Eastern philosophers soon found it necessary to run into Pantheism; for, the necessity of unity pressing on them, they found no other way of escape except to make God the soul of the world. But, the gulf between matter and divinity still remaining, they had to fall upon two principles, the material and spiritual; and, not willing to identify the original spiritual principle with matter, darkness, and evil, they fell upon the idea of two antagonistic beings or gods, a good and an evil one, the god of light and the god of darkness, the god of matter and the god of spirit Ahriman the evil principle, and Ormuzd the good.
2. Dualism in the Christian Age. — This Oriental Dualism, carried out into the various departments of nature and mind, and embellished by innumerable beautiful fancies, had a great charm for the imagination of even the primitive Christian mind; and it seemed also to form a certain kind of natural and easy alliance with the doctrines of good and evil, God and Satan, spirit and matter, in the human constitution, as these are unfolded in the Christian revelation, so that this dualistic mode of thinking failed not to insinuate itself largely into the thinking of many in the primitive Church. It has also revealed itself, more or less, in various sects and systems in every period of Christian history, and its false theories have often troubled the mind of the Church in the development and statement of its dogmas. Thus in Gnosticism, and especially in the Docetic phase of it, Dualism enters as a ruling element. The Gnostics found it difficult to explain the existence of the sensible world, and especially the existence of evil, on the direct assumption of one absolutely good Being. Hence they mixed into their theory some elements of the Oriental philosophy. "They thought themselves compelled to combine with the doctrine of emanation that of Dualism, in order, by the commixture of two hostile realms, by the products of two opposite principles, to explain the origin of a world not answering to the divine idea, with all the defects cleaving to it, all the evils it contains" (Neander, Hist. of the Chr. Church, Bohn's ed. 2:14). For the Manichaean Dualism, SEE MANICHEISM; and for that of the Cathari, SEE CATHARI.
That the ascetic tendencies of the early Christian age were strongly stimulated, if not unconsciously caused by a leaven of Dualism, can hardly be doubted. "A dark instinct of a state of abnormal and dangerous antipathy to God leads the devotee to take vengeance in time upon that part of himself which is outside, and which may be hardly treated, and even tortured, at far less cost than the renewal of the spirit of his mind, and the bringing of his whole inner man back to gravitate towards God instead of turning upon itself. Manes endeavored to unite Christianity and the noblest form of Oriental paganism in his brilliant and elaborately constructed speculative system. The Church repulsed the heresiarch because of his personal pretensions, his rival hierarchy, and his too open importations from the religion of Persia; but it was not the less profoundly modified by the tendencies which it nominally rejected. Monasticism in Syria and Egypt was the direct result of the contact of degenerating Christianity with pagan habits of thought. The idea that abstinence from food was meritorious in itself, the notion of impurity attached to the sexual relation, the growing tendency to look upon marriage as a state less holy than celibacy these were so many triumphs of the invading pagan conception. The errors and extravagances of the ascetic life were especially prevalent in the Eastern Church. Schmid quotes authorities to show that remembrances of Manichaeism were long kept up in Oriental convents, and also that sundry Greek monks, in their solitude, imagined they had constantly to struggle with the devil, whose power they magnified until they put him almost on a rank with God" (London Review, April 1855, page 10; see also Lea, Sacerdotal Celibacy, Phila. 1867, page 42 sq.).
The progress of philosophy and theology in all Christian ages has been a continuous struggle to overcome Dualism, to bring God and the world, the infinite and the finite, heaven and earth, spirit and matter together, and to do this without violence to the essential nature of either, by, on the one hand, confusing them, or, on the other, annihilating one or the other by identification of them. Pantheism, as it has sprung up on the arena of modern theological investigation, has been an earnest, though mistaken effort to overcome Dualism. Much as Pantheism is to be abhorred and dreaded, yet ought its service to be acknowledged in helping philosophy and theology to master Dualism. It has both suggested and stimulated the movement that aims at the creation of a christological theology, and we may also say philosophy, which professes, not without hope of success, to overcome that mischievous Dualism which knows only to negate, and which, in a cowardly manner, has only given up the great fundamental problems. It holds that the great gulf can be, and can only be, bridged by the God man in whose mysterious person all dualismn is overcome the center and perennial source of all life and thought, the principle of all unities and the unity of all principles, the whole of all that is divided, the harmony of all manifoldness and diversity, the center of all science, and the imperial, incarnate Word of all authority and truth, the final rest of all minds, as he is also of all hearts. Hardwick, Christ and other Masters (London. 1863, 2 volumes, 12mo); Dorner, Doctrine of the Person of Christ (see Index); Hagenbach, Hist. of Doctrines, Smith's ed., § 51, 127; Theol. Stud. u. Kritiken (1837), page 357; Lange, Life of Christ (Edinb. 1854, 6 volumes, 8vo), 1:135 sq.; H. Schmid, in Herzog, Real Encykl. 19:432.