Monism and pluralism are families of views about the roles of unity and multiplicity in the structure of reality. According to this view, even a complete understanding of physics would not render sciences dedicated to higher levels, such as psychology, obsolete. Non-reductive physicalists hold that everything is ultimately physical while insisting that higher-level psychological facts cannot be reduced to fundamental physics. In this sense, there can be matter without biological life, whereas life is built upon matter and depends on it. Lower levels, by contrast, operate according to more basic mechanisms and are prior to the higher ones.

Values

A central topic in ontology is the categories of being—fundamental classes that map out a comprehensive inventory of reality. Becoming, by contrast, covers change, like when an entity shifts from one state of being to another. Other suggested criteria identify reality with what is observable, measurable,a coherent,b useful, objective, intersubjective, or fundamental. It focuses on how things seem to be, distinguishing real appearances, which are as they seem, from illusory ones, which are not as they seem.
It comprises beliefs, ideas, and attitudes that form a background against which people interpret experiences, make decisions, and navigate life. By contrast, Arthur Schopenhauer (1788–1860) criticized German idealism and held that a blind, irrational will is the underlying principle of reality. Immanuel Kant (1724–1804) rejected the possibility of objective knowledge of the things in themselves, arguing instead that all experience is shaped by the innate structures of human cognition. Plato (c. 427 – c. 347 BCE) argued for the existence of a realm of eternal forms or ideas in addition to the material world of mutable entities.

• Epistemology, another philosophical subdiscipline, explores how people can know reality.
• In a broad sense, appearances are not limited to what people perceive but can also include memories, beliefs, and thoughts.
• It focuses on how things seem to be, distinguishing real appearances, which are as they seem, from illusory ones, which are not as they seem.
• For example, a person may be a realist about universals and an anti-realist about values.
• Some philosophers, such as Alexius Meinong, hold that being is a broader concept than reality, encompassing nonexistent objects, such as merely possible or incomplete objects, in addition to real or actual ones.
• The school of Vaisheshika arose roughly in the 2nd century BCE and developed a system of six fundamental categories of being.
• In psychoanalytic theory, the reality principle is a proposed mechanism that counteracts the pleasure principle, delaying immediate gratification when it collides with the demands of external reality.

For example, one view suggests that macroscopic objects, such as a chair, depend on the microscopic objects that underlie them, such as elementary particles. The structure of reality concerns the fundamental patterns of being, describing how entities are organized and interact with each other. According to a common view, concrete objects exist in space and time, such as a flower, a horse, and a ship. Events are proposed constituents of reality that occur in time, such as the discovery of penicillin and the Second World War.

Related concepts

In psychoanalytic theory, the reality principle is a proposed mechanism that counteracts the pleasure principle, delaying immediate gratification when it collides with the demands of external reality. For example, value theory is concerned with the reality of values, and the philosophy of mathematics explores in what sense mathematical objects, like numbers and sets, form part of reality. Different worldviews offer distinct answers to existential questions about meaning, morality, and the nature of reality, such as the contrast between religious and secular worldviews. A worldview is a comprehensive framework for understanding reality and humanity’s place within it. One perspective holds that such objects are illusory or unreal because they lack existence in the physical world outside the simulation. The reality–virtuality continuum is a theoretical framework that posits a continuous scale of mixed reality forms.
This view emphasizes that reality is encountered, rather than invented, and can resist or frustrate beliefs and desires, unlike malleable imaginary creations. Another influential proposal treats mind-independence as a criterion of reality, arguing that real entities do not depend on how people think about them. The Eleatic principle is controversial because it is typically taken to deny that abstract objects studied in fields like mathematics, such as numbers, are real. However, stories about Santa Claus, such as written texts in children’s books, are part of reality since they can influence how people think. Discussed in ancient Greek philosophy as the Eleatic principle, it states that to be real is to be able to produce changes and to be affected by them. Criteria of reality are proposed features or standards that distinguish real entities from unreal ones.
It overlaps with the cognitive sciences, which investigate how cognitive processes transform information about the world, and with neuroscience, which studies the brain activities underlying such processes. It concerns the question of how mental and linguistic entities, such as thoughts and words, can establish contact with reality by successfully referring to things in the world. It focuses on how individuals experience reality and how conscious states are intentional or directed towards entities other than themselves. Epistemology, another philosophical subdiscipline, explores how people can know reality. They examine what it means for something to be real, how entities are divided into different categories of being, and which entities exist at the most fundamental level.

Realism and anti-realism

Anti-realism about abstract objects in mathematics takes various forms, including, but not limited to, fictionalism. Anti-realists hold that there are no abstract objects and offer alternative explanations. Realists and anti-realists about abstract objects debate whether, or in what sense, such entities form part of reality. Nominalism, another anti-realist view, rejects both mental and non-mental interpretations of universals. For example, a person may be a realist about universals and an anti-realist about values. In this sense, realism and anti-realism encompass many domain-specific positions across diverse fields.
Inspired by Leibniz, David Lewis (1941–2001) developed modal realism, maintaining that possible worlds are as real as the actual world. E. Moore (1873–1958) drew on common sense and empirical science to oppose idealism, emphasizing that the world exists independently of the mind. Responding to Kant’s philosophy, the German idealists sought a unifying principle as the foundation of all reality. In Hindu philosophy, the school of Advaita Vedanta emerged in the 8th century and held that the world of everyday appearances is an illusion, contrasting it with the ultimate reality of Brahman. Inspired by Plato’s realm of forms, Plotinus (c. 204 – c. 270 CE) identified the One as the supreme principle underlying all of reality. His student Aristotle (384–322 BCE) proposed a system of ten categories describing the fundamental constituents of reality.

• This view emphasizes that reality is encountered, rather than invented, and can resist or frustrate beliefs and desires, unlike malleable imaginary creations.
• In a narrow sense, being contrasts with becoming, and denotes stable or permanent aspects of reality.
• Philosophers discuss various sources of knowledge as ways of how this cognitive contact is established, including perception, introspection, reason, memory, and testimony.
• It overlaps with the cognitive sciences, which investigate how cognitive processes transform information about the world, and with neuroscience, which studies the brain activities underlying such processes.
• One strand of the field analyzes culture-specific worldviews and compares them across societies.
• Phenomenalism, a related view, reduces physical objects to collections of actual or possible sensory experiences.

Levels of reality

It characterizes realism as the view that the truth or meaning of sentences is determined by external standards or mind-independent reality. A semantic approach to the debate between realism and anti-realism, proposed by Michael Dummett, argues that the underlying disagreement https://www.zumospin.net/ concerns the meaning of statements rather than the existence of entities. On this view, reality is made up of countless concrete worlds existing in parallel without interacting with one another. In the social sciences, critical realism holds that observable events in the social world only partially disclose reality. Local realism is a view that combines the principle of locality with the notion that there are definite physical properties, whether or not they are being observed by someone.

Accordingly, worldviews address not only theoretical matters but also practical and evaluative outlooks about what matters and how one should act. Another view maintains that they are real as digital objects with genuine existence and causal powers, residing within and being constituted by computational processes. Similarly, virtual reality worlds may incorporate real-world objects into the simulation or be entirely virtual.l Although it is not a widely accepted position, various thought experiments undermining the reliability of human cognitive faculties are discussed in the academic literature. It denies the existence of knowledge in any form or domain, arguing that knowledge is impossible. These limitations indicate a gap whereby reality is not fully captured and exceeds knowledge.
It holds that the debate is not based on a substantive disagreement but arises instead from conceptual confusions. For example, metaphysical idealism asserts that everything is essentially mental, for instance, by understanding material objects as ideas in the mind. In this sense, reality does not depend on human knowledge or consciousness and exists apart from them, including the aspects that no one is aware of. The widely accepted Big Bang theory holds that the universe began about 13.8 billion years ago, initially in an extremely hot, dense state, expanding and cooling ever since.

More general constraints arise from limits of human cognitive faculties rather than situation-specific circumstances, such as facts too complex for anyone to conceive. Testimony is a transmission of knowledge from one person to another through communication.k Memory is the capacity to store information from other sources and make it available to cognitive processes when needed. Reason is the ability to draw logical inferences and arrive at truths independent of immediate sensory input. Anti-realism is understood as a view that identifies the meaning of a statement with the evidence that would support it or the conditions under which a person is justified in asserting it. It opposes the idea that world and mind are essentially correlated, emphasizing the mind-independent nature of reality beyond the way humans perceive and think about it.