Platonic realism in the context of "Platonism"

Ontology is the philosophical study of being. It is traditionally understood as the subdiscipline of metaphysics focused on the most general features of reality. As one of the most fundamental concepts, being encompasses all of reality and every entity within it. To articulate the basic structure of being, ontology examines the commonalities among all things and investigates their classification into basic types, such as the categories of particulars and universals. Particulars are unique, non-repeatable entities, such as the person Socrates, whereas universals are general, repeatable entities, like the color green. Another distinction exists between concrete objects existing in space and time, such as a tree, and abstract objects existing outside space and time, like the number 7. Systems of categories aim to provide a comprehensive inventory of reality by employing categories such as substance, property, relation, state of affairs, and event.

Ontologists disagree regarding which entities exist at the most basic level. Platonic realism asserts that universals have objective existence, while conceptualism maintains that universals exist only in the mind, and nominalism denies their existence altogether. Similar disputes pertain to mathematical objects, unobservable objects assumed by scientific theories, and moral facts. Materialism posits that fundamentally only matter exists, whereas dualism asserts that mind and matter are independent principles. According to some ontologists, objective answers to ontological questions do not exist, with perspectives shaped by differing linguistic practices.

In metaphysics, nominalism is the view that universals and abstract objects do not actually exist other than being merely names or labels. There are two main versions of nominalism. One denies the existence of universals—that which can be instantiated or exemplified by many particular things (e.g., strength, humanity). The other version specifically denies the existence of abstract objects as such—objects that do not exist in space and time.

Most nominalists have held that only physical particulars in space and time are real, and that universals exist only post res, that is, subsequent to particular things. However, some versions of nominalism hold that some particulars are abstract entities (e.g., numbers), whilst others are concrete entities – entities that do exist in space and time (e.g., pillars, snakes, and bananas). Nominalism is primarily a position on the problem of universals. It is opposed to realist philosophies, such as Platonic realism, which assert that universals do exist over and above particulars, and to the hylomorphic substance theory of Aristotle, which asserts that universals are immanently real within them; however, the name "nominalism" emerged from debates in medieval philosophy with Roscellinus.

Moderate realism (also called immanent realism) is a position in the debate on the metaphysics of universals which holds that there is no realm in which universals exist (in opposition to Platonic realism, which asserts the existence of abstract objects), nor do they really exist within particulars as universals, but rather universals really exist within particulars as particularised, and multiplied.

Anthroposophy is a spiritual new religious movement which was founded in the early 20th century by the esotericist Rudolf Steiner that postulates the existence of an objective, intellectually comprehensible spiritual world, accessible to human experience. Followers of anthroposophy aim to engage in spiritual discovery through a mode of thought independent of sensory experience. Though proponents claim to present their ideas in a manner that is verifiable by rational discourse and say that they seek precision and clarity comparable to that obtained by scientists investigating the physical world, many of these ideas have been termed pseudoscientific by experts in epistemology and debunkers of pseudoscience.

Anthroposophy has its roots in German idealism, Western and Eastern esoteric ideas, various religious traditions, and modern Theosophy. Steiner chose the term anthroposophy (from Greek ἄνθρωπος anthropos-, 'human', and σοφία sophia, 'wisdom') to emphasize his philosophy's humanistic orientation. He defined it as "a scientific exploration of the spiritual world"; others have variously called it a "philosophy and cultural movement", a "spiritual movement", a "spiritual science", "a system of thought", "a speculative and oracular metaphysic", "system [...] replete with esoteric and occult mystifications", or "a spiritualist movement", or folie a culte, or "positivistic religion", or "a form of 'Christian occultism'", or "new religious movement" and "occultist movement".