Realism from a metaphysical standpoint may be described as a theory that the world of our experience is real and not merely apparent or illusory. It may be compatible with metaphysical monism (the theory that reality consists of a single substance), metaphysical dualism (the theory that reality consists of only two substances, e.g. mind and matter) or metaphysical pluralism (the theory that reality consists of many different substances).
A substance may be defined in a variety of ways. It may be described as simply "that which is." It may also be described as that in which the properties of a thing inhere, or as that which has properties but is not itself a property. It may also be described as that without which a thing would not exist (or the essence of a thing, that without which the thing would not be what it is, rather than some other thing).
Aristotle (in the Metaphysics) says that substance is the only category of being that does not belong to, and cannot be predicated of, any other category of being. All of the other categories of being may be predicated of a substance, but substance itself as a category of being does not depend on any of the other categories. It is both essence (form) and substratum (matter). The substance of a thing is the particular nature of that thing. The being of any particular thing is primarily defined by what is (i.e. by its substance, its "whatness" or quiddity).
Spinoza (in the Ethics, 1677) defines a substance as that which is "in itself" (that which does not depend on something else for its being), and as that which is conceived through itself (that which does not depend on something else for its conception).
The theory that reality consists of many, or perhaps an infinite number of, substances (real things, facts, entities, or events), for which we may use the abbreviated term "reals," is a kind of realism that may be compatible with metaphysical idealism (the theory that ultimate reality is mental, and that the world consists of ideas), provided that realism and idealism are not defined as being contradictory to each other (with realism, on the one hand, being defined as a theory holding that the world exists independently of mind, and idealism, on the other hand, being defined as a theory holding that the world does not exist independently of mind). The "reals" posited by this kind of realism may be mental, physical, or both, without any necessary self-contradiction in this kind of theory.
If the "reals" that constitute reality are different substances and not the same substance, then this kind of realism may be a metaphysical pluralism that is in opposition to metaphysical monism. A version of this kind of theory was formulated by the German philosopher Gottfried Wilhelm Leibniz (1646-1716) in The Monadology (La Monadologie, 1714), and another version of this kind of theory was proposed by the German philosopher Johann Friedrich Herbart (1776-1841) in his General Metaphysics (Allgemeine Metaphysik, 1828-9). Herbart's version will hereafter be referred to as Herbartian realism (HR).
Leibniz defines "monads" as simple substances that are the basic elements of things,1 while Herbart refers to "reals" as the reality of attributes of being.2
However, "reals" may be defined in other kinds of metaphysical pluralism as not only substances, attributes, qualities, or properties, but also as objects, relations, kinds, and ways (or modes) of being. "Reals" may be the basic elements, constituents, or building blocks of reality. Thus, Leibnizian monadology or Herbartian realism (HR) may represent a kind of foundationalism or reductionism, holding that reality, from an epistemological viewpoint, can be reduced to various basic or foundational elements from which all other elements are derived.
According to this viewpoint, reals are simple substances from which compound and complex substances are derived. As simple substances, they do not consist of parts, and therefore cannot be further reduced to simple parts. This epistemological or ontological viewpoint may be a kind of reism or concretism in its reification or concretization of real things or entities (in opposition to abstractionism, the theory that abstract objects are real and actually exist). Change, becoming, and transformation may be explained by rearrangements of the various building blocks, basic elements, monads, or "reals" that constitute reality. A deterministic (mechanistic, essentialist) or indeterministic (inessentialist, accidentalist) viewpoint may be taken with regard to the origin of this change, becoming, or transformation.
Ludwig Wittgenstein (in the Tractatus Logico-Philosophicus, 1922), says that the world is the totality of "atomic facts," and that these facts are expressed by propositions. Elementary propositions assert the existence or nonexistence of atomic facts, and are true or false depending on whether these facts exist or do not exist. Every logical proposition is a model of reality.
Bertrand Russell (in a series of lectures entitled "The Philosophy of Logical Atomism," 1918-19), says that atomic facts are the simplest kind of facts, and that they are expressed by atomic propositions. Atomic propositions are propositions that express atomic facts. Facts are things (objects, events, states of affairs) about which we may have beliefs, and these beliefs may be expressed by propositions. The world may thus be logically analyzed in terms of the facts that it contains. Russell says that this approach is a logical, rather than physical, atomism, because it is concerned with a logical rather than physical analysis of the real world.3
Rudolf Carnap (in The Logical Structure of the World, 1964) describes the logical structure of the world as a system of hierarchical construction in which the objects of each successive level are constructed from simpler or more elementary objects. At the most basic level of construction are basic objects, which include basic elements and basic relations. Basic elements are elementary experiences that are not constructed from simpler or more elementary objects. Rather, they are immediately given as formal objects. Thus, they cannot be analyzed into proper constituents, and cannot be given property descriptions. They can only be given relation descriptions.
John R. Searle (in The Construction of Social Reality, 1995) describes social and institutional facts as the building blocks of social reality, and he says that social facts are objective facts, insofar as they are ultimately based on physical facts and are not merely a matter of subjective preference or opinion.
If "reals" are the basic facts of reality, then monadic realism (MR) may be a kind of factualism, in accordance with epistemological objectivism and in opposition to subjectivism. It may be reconcilable with absolutism or relativism with regard to whether the "reals" that constitute reality are absolute or relative (to observation, to perception, or to a particular viewpoint). If the real is the given, and the "reals" of MR are the given facts that constitute reality, then MR is also in opposition to constructivism. Reality is not constructed by a subject; it is given to, or present for, perception, regardless of how extensive or limited a subject's perception of it might be.
MR is also a theory of the multiple, of the infinite, of diversity.
If monadic realism is a theory that reality is monadic and individual, and if it is a theory that reality consists of many different entities, substances, selves, objects, or concepts, then it also implies that reality is disjunctive, split, or discontinuous, and that there are many distinct or independent realities.
If the reals proposed by monadic realism are ultimate reality and are the ultimate facts of the world, are they knowable or unknowable? If our knowledge of the basic facts of reality is restricted to the phenomena of sensory experience, or to truths that are derived from the phenomena of sensory experience, is this theory a kind of phenomenalism or sensationalism?
Are reals the noumena of which the objects of sensory experience are the phenomena?4 Are there unknowable objects (noumena) that correspond to the knowable objects (phenomena) of sensory experience? According to Immanuel Kant (in the Critique of Pure Reason, 1781), the objects of cognition can be divided into phenomena and noumena. Phenomena are objects of possible experience, but noumena are not objects of possible experience.
What kinds of reality are there? How are they similar or different? How do we distinguish between moral, social, cultural, historical, physical, material, formal, practical, subjective, objective, and virtual reality?
1Gottfried Wilhelm Leibniz, in G.W. Leibniz's Monadology: An Edition for Students, by Nicholas Rescher (Pittsburgh: University of Pittsburgh Press, 1991) p. 17
2Johann Friedrich Herbart, "Allgemeine Metaphysik nebst den Anfängen der Philososphischen Naturlehre," in Johann Friedrich Herbart's Sämtliche Werke, Herausgegeben von G. Hartenstein, Vierter Band, (Hamburg and Leipzig, Leopold Voss, 1886, s. 207 p. 86)
3Bertrand Russell, "The Philosophy of Logical Atomism," in The Monist (Oct. 1918), p. 497.
4Charles De Garmo, Herbart and the Herbartians (Honolulu: University Press of the Pacific) p. 28.