Metaphysical pluralism in philosophy is the multiplicity of metaphysical models of the structure and content of reality, both as it appears and as logic dictates that it might be, as is exhibited by the four related models in Plato's
Republic and as developed in the
contrast between
phenomenalism and
physicalism. Pluralism is in contrast to the concept of monism in metaphysics, while
dualism is a limited form, a pluralism of exactly two models, structures, elements, or concepts. A distinction is made between the metaphysical identification of realms of reality and the more restricted sub-fields of ontological pluralism (that examines what exists in each of these realms) and
epistemological pluralism (that deals with the methodology for establishing knowledge about these realms).
Ancient pluralism In ancient Greece,
Empedocles wrote that they were fire, air, water and earth, although he used the word "root" rather than "element" (στοιχεῖον;
stoicheion), which appeared later in Plato. From the association (φιλία;
philia) and separation (νεῖκος;
neikos) of these indestructible and unchangeable root elements, all things came to be in a fullness (πλήρωμα;
pleroma) of ratio (λόγος;
logos) and proportion (ἀνάλογος;
analogos). Similar to Empedocles,
Anaxagoras was another Classical Greek philosopher with links to pluralism. His metaphysical system is centered around mechanically necessitated
nous which governs, combines and diffuses the various "roots" of reality (known as
homoioneroi). Unlike Empedocles' four "root elements" and similar to
Democritus' multitude of
atoms (yet not physical in nature), these
homoioneroi are used by Anaxagoras to explain the multiplicity in reality and becoming. This pluralist theory of being influenced later thinkers such as
Gottfried Wilhelm Leibniz's theory of
monads and
Julius Bahnsen's idea of
will henades. The notion of a governing
nous would also be used by
Socrates and
Plato, but they will assign it a more active and rational role in their philosophical systems.
Aristotle incorporated these elements, but his
substance pluralism was not material in essence. His
hylomorphic theory allowed him to maintain a
reduced set of basic material elements as per the
Milesians, while answering for the ever-changing flux of
Heraclitus and the unchanging unity of
Parmenides. In his
Physics, due to the continuum of
Zeno's paradoxes, as well as both logical and empirical considerations for natural science, he presented numerous arguments against the
atomism of
Leucippus and
Democritus, who posited a basic duality of
void and
atoms. The atoms were an infinite variety of
irreducibles, of all shapes and sizes, which randomly collide and mechanically hook together in the void, thus providing a reductive account of changeable figure, order and position as aggregates of the unchangeable atoms. == Ontological pluralism ==