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.
On this view, higher levels show greater complexity and new phenomena but depend on the lower ones and could not exist without them. Some philosophical approaches rely on the idea of fundamentality and dependence to analyze the world in terms of levels or layers, such as material, biological, psychological, and social reality. In the Hindu tradition, it is often identified with Brahman as the all-pervasive reality and the supreme principle grounding all being.
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.
Various criteria for distinguishing real from unreal entities have been proposed, including causal powers, mind-independence, and being non-illusory. It is often contrasted with appearance, opposing what is with what seems to be, although the accuracy and fundamentality of this contrast are disputed.
Computer scientists discuss how systems of knowledge representation can organize information about reality and make it accessible to computational processes. Reality testing is another suggested psychological function in which individuals distinguish intrapsychic from external events to assess how their experience aligns with reality. 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.
Viewpoints on reality
In this sense, realism and anti-realism encompass many domain-specific positions across diverse fields. Anti-realism rejects this view, arguing instead that there is no external world or that reality depends in certain respects on mental processes, subjective perspectives, or social conventions. Realism and anti-realism are families of views concerning the mind-independence of reality. Some interpretations of quantum mechanics hold that measurement outcomes are inherently probabilistic, thereby rejecting causal determinism, but this is not true for all interpretations.g According to this view, what happened in the past fixes what will happen in the future, including human behavior. Causal determinism is the view that every event is fully determined or necessitated by prior events.
Realism and anti-realism
It holds that the debate is not based on a substantive disagreement but arises instead from conceptual confusions. Relativism, another form of anti-realism, holds that what counts as real varies based on one’s perspective or conceptual framework. For example, metaphysical idealism asserts that everything is essentially mental, for instance, by understanding material objects as ideas in the mind. The widely accepted Big Bang theory holds that the universe began about 13.8 billion years ago, initially in an extremely hot, dense state, mister golden expanding and cooling ever since.
- The simulation hypothesis is the view that the whole world and everything within it is a simulated reality, including humans.
- In a slightly different sense, reality is not the totality itself but an aspect shared by all its constituents.
- In the social sciences, critical realism holds that observable events in the social world only partially disclose reality.
- According to conventionalism, the truth of mathematical statements rests on linguistic conventions or definitions, rather than on their relation to language-independent reality.
- Lower levels, by contrast, operate according to more basic mechanisms and are prior to the higher ones.
- 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.
- In a broad sense, appearances are not limited to what people perceive but can also include memories, beliefs, and thoughts.
- More general constraints arise from limits of human cognitive faculties rather than situation-specific circumstances, such as facts too complex for anyone to conceive.
- A semantic approach to the debate between realism and anti-realism, proposed by Michael Dummett, argues that the underlying disagreement concerns the meaning of statements rather than the existence of entities.
- This view emphasizes that reality is encountered, rather than invented, and can resist or frustrate beliefs and desires, unlike malleable imaginary creations.
- Epistemology, another philosophical subdiscipline, explores how people can know reality.
- While some skeptical scenarios use the idea of a simulated reality to challenge the reliability of human cognition, contemporary technologies such as augmented reality and virtual reality can also inform experience.
Inspired by Leibniz, David Lewis (1941–2001) developed modal realism, maintaining that possible worlds are as real as the actual world. Responding to Kant’s philosophy, the German idealists sought a unifying principle as the foundation of all reality. 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. In ancient Greek philosophy starting in the 6th century BCE, the pre-Socratics discussed the first principles from which all things arise. 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, the laws of thermodynamics describe how heat and other forms of energy behave, such as the idea that the total amount of energy is always conserved. Existence monism contrasts with existence pluralism, which aligns more closely with everyday experience by asserting that reality is made up of many objects. There are different ways to conceptualize the relation between fundamental and non-fundamental entities, including the ideas of ontological dependence, metaphysical grounding, reduction, supervenience, and emergence.
According to conventionalism, the truth of mathematical statements rests on linguistic conventions or definitions, rather than on their relation to language-independent reality. Anti-realism about abstract objects in mathematics takes various forms, including, but not limited to, fictionalism. Fictionalists argue that discourse about abstract objects concerns fictional entities within make-believe frameworks. Anti-realists hold that there are no abstract objects and offer alternative explanations.