Leibniz's Monadology provides a concise exposition of the central concept of his metaphysics: the Monad (from Greek monas, unit).----The present volume includes a side-by-side presentation of the original French (drawn from the Nolen edition of 1881) and an English translation (adapted from the translation of Frederic Henry Hedge, from The Journal of Speculative Philosophy, Vol. I, No. 3 (1867).----The philosophical use of the term Monad originated with Pythagoras, where it informed the basis of his numerical philosophy. The idea has come down through the centuries, in one form or another, as a core tenet of idealistic philosophy or spirituality. Leibniz adopted the term in his own explorations, where he determined that the only real beings are what he called "simple substances," of which all compound bodies or beings are but aggregates. He himself briefly explains, thus:"I do not eliminate body, but reduce it to what it is, for I show that corporeal mass . . . is not a substance, but a phenomenon resulting from simple substances, which alone have unity and absolute reality.""According to Leibniz there can be but one ultimate cosmic reality or Monad, the universe; but he recognizes an innumerable multiplicity of monads which pervade the universe, copies or reflections of the universal monad regarded as real except in their relation to the universal monad. He divides his derivative monads into three classes: rational souls; sentient but irrational monads; and material monads, or organic and inorganic bodies. As regards the material monads, while recognizing that corporeal matter is compound, and the attributes by which we perceive it unreal, unlike Berkeley, he does not deny its existence but regards it essentially as monadic. Thus his universe is an aggregate of individuals. The relations of these individuals to each other and to the universal is a supreme harmony, implying both individuality and coordination, thus reconciling the antinomy of bonds of law and freedom. The interrelations of various groups of monads is as a series of hierarchies." (Theos. Encycl. Gloss.)The Monad, and monads, holds also a central place in modern Theosophical philosophy, where an attempt is made to rectify some philosophical and metaphysical faults in Leibniz's approach. The interested student may find much of interest on the topic in H. P. Blavatsky's The Secret Doctrine (1888), in particular the section titled "Gods, Monads, and Atoms," vol. I, pp. 610 etc.