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. Moral skepticism is the view that there is no moral knowledge, for instance, that one cannot know whether a given behavior is morally right or wrong. Some forms target specific domains of knowledge, such as religious skepticism, which denies that beliefs about God or other religious doctrines amount to knowledge. Philosophers examine various limitations of knowledge or obstacles to the cognitive contact with reality. Philosophers discuss various sources of knowledge as ways of how this cognitive contact is established, including perception, introspection, reason, memory, and testimony.
It holds that this practice can be useful in some contexts without ascribing substantive or framework-independent reality to such entities. Relativism, another form of anti-realism, holds that what counts as real varies based on one’s perspective or conceptual framework. Phenomenalism, a related view, reduces physical objects to collections of actual or possible sensory experiences. In the broadest sense, realism is the view that the external world and its constituents exist as they do regardless of how people perceive or think about them.

Realism and anti-realism

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.

• Criteria of reality are proposed features or standards that distinguish real entities from unreal ones.
• One perspective holds that such objects are illusory or unreal because they lack existence in the physical world outside the simulation.
• 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.
• Anti-realism about abstract objects in mathematics takes various forms, including, but not limited to, fictionalism.
• For example, if a planet or a virus is real then it exists on its own and behaves according to its nature, even if people are unaware or hold false beliefs about it.
• The structure of reality concerns the fundamental patterns of being, describing how entities are organized and interact with each other.
• 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.

Related concepts

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.

Levels of reality

In this sense, it is the state of being real or what all real entities have in common, separating them from unreal or illusory ones. In a slightly different sense, reality is not the totality itself but an aspect shared by all its constituents. Contemporary technology in the form of augmented and virtual reality can inform experience and raises questions about the ontological status of virtual objects. Other discussions examine space and time as frameworks that organize relations among entities, and laws of nature describing regularities or general patterns of how entities interact and changes unfold. 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.

Realism and anti-realism

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.

On this view, unobservable entities may be invoked in theory construction to aid prediction but should not be taken to exist. Scientific realism is the view that the best scientific theories provide an accurate description of a mind-independent world. Error theory asserts that all value statements are false because there are no values.i Another form of anti-realism maintains that value statements are neither true nor false but meaningless. According to subjectivism, values depend on the attitudes and preferences of individuals. Non-naturalism, another form of realism, maintains that values differ significantly from empirical properties and belong to another domain of reality.

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. Laws of nature play a central role in the physical sciences by providing frameworks for predicting outcomes under specified conditions.

• It comprises beliefs, ideas, and attitudes that form a background against which people interpret experiences, make decisions, and navigate life.
• Testimony is a transmission of knowledge from one person to another through communication.k
• Realists hold that values are objective features of reality, meaning that there are mind-independent facts about whether something is good or bad, irrespective of subjective beliefs or personal preferences.
• It is often contrasted with appearance, opposing what is with what seems to be, although the accuracy and fundamentality of this contrast are disputed.
• Some outlooks suggest that only the fundamental level is ultimately real, arguing that non-fundamental entities are in some sense eliminable since reality can be described without them.
• Scientific realism is the view that the best scientific theories provide an accurate description of a mind-independent world.
• Formalism, another form of anti-realism, understands mathematics as a practice of symbol manipulation, suggesting that mathematical truth is grounded in whether the manipulation rules permit the construction of a proof.

For example, psychologism asserts that mathematical objects are mental constructions or ideas rather than abstract objects. Fictionalists argue that discourse about abstract objects concerns fictional entities within make-believe frameworks. According to conceptualism, universals exist in the mind as concepts through which people categorize and order their impressions, acting as tools of cognitive organization rather than properties of external entities. Platonism about universals holds that they are part of reality in their own right, independent of the particular entities that instantiate them.
For example, one view suggests that macroscopic objects, such as a chair, depend on the microscopic objects that underlie them, such https://www.zumospin.net/ 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.
In a broad sense, appearances are not limited to what people perceive but can also include memories, beliefs, and thoughts. Unreal entities, by contrast, depend for their existence on thoughts and ideas; they would not arise or would vanish without the mental activity creating or sustaining them. A related topic concerns the possibility and limits of knowledge as a successful cognitive contact with reality. Anti-realism, by contrast, holds that certain aspects of reality depend on mental processes, subjective perspectives, or social conventions.
In the broadest sense, being is the most general category that applies to everything and contrasts only with nothingness. The term reality overlaps with various related concepts, such as being, existence, world, actuality, and truth. This view contrasts being real with being fake, like the distinction between a real duck and a fake one used as a decoy.
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. Some outlooks suggest that only the fundamental level is ultimately real, arguing that non-fundamental entities are in some sense eliminable since reality can be described without them.
Skepticism about metaphysics holds that it is not possible to know the fundamental nature of reality, such as claims about categories of being or the existence of universals. It holds that the scientific view of the world is either exactly or at least approximately true by presenting reality as it is. For example, emotivism holds that value statements express emotional attitudes of subjective approval or disapproval rather than objective facts. Anti-realist views reject the mind-independent existence of values and can take various forms. Realists hold that values are objective features of reality, meaning that there are mind-independent facts about whether something is good or bad, irrespective of subjective beliefs or personal preferences.