Perception in the context of "Vision (sense)"

Experience refers to conscious events in general, more specifically to perceptions, or to the practical knowledge and familiarity that is produced by these processes. Understood as a conscious event in the widest sense, experience involves a subject to which various items are presented. In this sense, seeing a yellow bird on a branch presents the subject with the objects "bird" and "branch", the relation between them and the property "yellow". Unreal items may be included as well, which happens when experiencing hallucinations or dreams. When understood in a more restricted sense, only sensory consciousness counts as experience. In this sense, experience is usually identified with perception and contrasted with other types of conscious events, like thinking or imagining. In a slightly different sense, experience refers not to the conscious events themselves but to the practical knowledge and familiarity they produce. Hence, it is important that direct perceptual contact with the external world is the source of knowledge. So an experienced hiker is someone who has actually lived through many hikes, not someone who merely read many books about hiking. This is associated both with recurrent past acquaintance and the abilities learned through them.

Many scholarly debates on the nature of experience focus on experience as a conscious event, either in the wide or the more restricted sense. One important topic in this field is the question of whether all experiences are intentional, i.e. are directed at objects different from themselves. Another debate focuses on the question of whether there are non-conceptual experiences and, if so, what role they could play in justifying beliefs. Some theorists claim that experiences are transparent, meaning that what an experience feels like only depends on the contents presented in this experience. Other theorists reject this claim by pointing out that what matters is not just what is presented but also how it is presented.

Epistemology is the branch of philosophy that examines the nature, origin, and limits of knowledge. Also called the theory of knowledge, it explores different types of knowledge, such as propositional knowledge about facts, practical knowledge in the form of skills, and knowledge by acquaintance as a familiarity through experience. Epistemologists study the concepts of belief, truth, and justification to understand the nature of knowledge. To discover how knowledge arises, they investigate sources of justification, such as perception, introspection, memory, reason, and testimony.

The school of skepticism questions the human ability to attain knowledge, while fallibilism says that knowledge is never certain. Empiricists hold that all knowledge comes from sense experience, whereas rationalists believe that some knowledge does not depend on it. Coherentists argue that a belief is justified if it coheres with other beliefs. Foundationalists, by contrast, maintain that the justification of basic beliefs does not depend on other beliefs. Internalism and externalism debate whether justification is determined solely by mental states or also by external circumstances.

Positivism is a philosophical school that holds that all genuine knowledge is either true by definition or positive – meaning a posteriori facts derived by reason and logic from sensory experience. Other ways of knowing, such as intuition, introspection, or religious faith, are rejected or considered meaningless.

Although the positivist approach has been a recurrent theme in the history of Western thought, modern positivism was first articulated in the early 19th century by Auguste Comte. His school of sociological positivism holds that society, like the physical world, operates according to scientific laws. After Comte, positivist schools arose in logic, psychology, economics, historiography, and other fields of thought. Generally, positivists attempted to introduce scientific methods to their respective fields. Since the turn of the 20th century, positivism, although still popular, has declined under criticism within the social sciences by antipositivists and critical theorists, among others, for its alleged scientism, reductionism, overgeneralizations, and methodological limitations. Positivism also exerted an unusual influence on Kardecism.

Knowledge is an awareness of facts, a familiarity with individuals and situations, or a practical skill. Knowledge of facts, also called propositional knowledge, is often characterized as true belief that is distinct from opinion or guesswork by virtue of justification. While there is wide agreement among philosophers that propositional knowledge is a form of true belief, many controversies focus on justification. This includes questions like how to understand justification, whether it is needed at all, and whether something else besides it is needed. These controversies intensified in the latter half of the 20th century due to a series of thought experiments called Gettier cases that provoked alternative definitions.

Knowledge can be produced in many ways. The main source of empirical knowledge is perception, which involves the usage of the senses to learn about the external world. Introspection allows people to learn about their internal mental states and processes. Other sources of knowledge include memory, rational intuition, inference, and testimony. According to foundationalism, some of these sources are basic in that they can justify beliefs, without depending on other mental states. Coherentists reject this claim and contend that a sufficient degree of coherence among all the mental states of the believer is necessary for knowledge. According to infinitism, an infinite chain of beliefs is needed.

The mind is that which thinks, feels, perceives, imagines, remembers, and wills. It covers the totality of mental phenomena, including both conscious processes, through which an individual is aware of external and internal circumstances, and unconscious processes, which can influence an individual without intention or awareness. The mind plays a central role in most aspects of human life, but its exact nature is disputed. Some characterizations focus on internal aspects, saying that the mind transforms information and is not directly accessible to outside observers. Others stress its relation to outward conduct, understanding mental phenomena as dispositions to engage in observable behavior.

The mind–body problem is the challenge of explaining the relation between matter and mind. Traditionally, mind and matter were often thought of as distinct substances that could exist independently from one another. The dominant philosophical position since the 20th century has been physicalism, which says that everything is material, meaning that minds are certain aspects or features of some material objects. The evolutionary history of the mind is tied to the development of nervous systems, which led to the formation of brains. As brains became more complex, the number and capacity of mental functions increased with particular brain areas dedicated to specific mental functions. Individual human minds also develop over time as they learn from experience and pass through psychological stages in the process of aging. Some people are affected by mental disorders, in which certain mental capacities do not function as they should.

Cognitions are mental activities that deal with knowledge. They encompass psychological processes that acquire, store, retrieve, transform, or otherwise use information. Cognitions are a pervasive part of mental life, helping individuals understand and interact with the world.

Cognitive processes are typically categorized by their function. Perception organizes sensory information about the world, interpreting physical stimuli, such as light and sound, to construct a coherent experience of objects and events. Attention prioritizes specific aspects while filtering out irrelevant information. Memory is the ability to retain, store, and retrieve information, including working memory and long-term memory. Thinking encompasses psychological activities in which concepts, ideas, and mental representations are considered and manipulated. It includes reasoning, concept formation, problem-solving, and decision-making. Many cognitive activities deal with language, including language acquisition, comprehension, and production. Metacognition involves knowledge about knowledge or mental processes that monitor and regulate other mental processes. Classifications also distinguish between conscious and unconscious processes and between controlled and automatic ones.

In linguistics, sound symbolism is the perceptual similarity between speech sounds and concept meanings. It is a form of linguistic iconicity. For example, the English word ding may sound similar to the actual sound of a bell.

Linguistic sound may be perceived as similar to not only sounds, but also to other sensory properties, such as size, vision, touch, or smell, or abstract domains, such as emotion or value judgment. Such correspondence between linguistic sound and meaning may significantly affect the form of spoken languages.

A sense is a biological system used by an organism for sensation, the process of gathering information about the surroundings through the detection of stimuli. Although, in some cultures, five human senses were traditionally identified as such (namely sight, smell, touch, taste, and hearing), many more are now recognized. Senses used by non-human organisms are even greater in variety and number. During sensation, sense organs collect various stimuli (such as a sound or smell) for transduction, meaning transformation into a form that can be understood by the brain. Sensation and perception are fundamental to nearly every aspect of an organism's cognition, behavior and thought.

In organisms, a sensory organ consists of a group of interrelated sensory cells that respond to a specific type of physical stimulus. Via cranial and spinal nerves (nerves of the central and peripheral nervous systems that relay sensory information to and from the brain and body), the different types of sensory receptor cells (such as mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors) in sensory organs transduct sensory information from these organs towards the central nervous system, finally arriving at the sensory cortices in the brain, where sensory signals are processed and interpreted (perceived).

Consciousness, at its simplest, is awareness of states or objects either internal to one's self or in one's external environment. However, its nature has led to millennia of explanations, analyses, and debate among philosophers, scientists, and theologians. Opinions differ about what exactly needs to be studied, or can even be considered consciousness. In some explanations, it is synonymous with mind, and at other times, an aspect of it.

In the past, consciousness meant one's "inner life": the world of introspection, private thought, imagination, and volition. Today, it often includes any kind of cognition, experience, feeling, or perception. It may be awareness, awareness of awareness, metacognition, or self-awareness, either continuously changing or not. There is also a medical definition that helps, for example, to discern "coma" from other states. The disparate range of research, notions, and speculations raises some curiosity about whether the right questions are being asked.