Knowledge is an awareness of facts ( descriptive knowledge), a familiarity with individuals and situations ( knowledge by acquaintance), or a practical skill ( procedural knowledge). Descriptive knowledge, 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. ...

Psychology is the scientific study of the mind and behavior. Its subject matter includes the behavior of humans and nonhumans, both conscious and unconscious phenomena, and mental processes such as thoughts, feelings, and motives. Psychology is an academic discipline of broad scope, crossing the boundaries between the natural and social sciences. A professional practitioner or researcher involved in the discipline is called a psychologist. Some psychologists can also be classified as behavioral or cognitive scientists. Some psychologists attempt to understand the role of mental functions in individual and social behavior. Others explore the physiological and neurobiological processes that underlie cognitive functions and behaviors. Biological psychologists seek an understanding of the emergent properties of brains, linking the discipline to neuroscience. As social scientists, psychologists aim to understand the behavior of individuals and groups. As part o ...

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 ...

An idea (from the Greek word: ἰδέα (idea), meaning 'a form, or a pattern') is the result of thought. Although the word is used in common usage, in philosophy, ideas can also be mental representational images of some object. Many philosophers have considered ideas to be a fundamental ontological category of being. The capacity to create and understand the meaning of ideas is considered to be an essential and defining feature of human beings. An idea arises in a reflexive, spontaneous manner, even without thinking or serious reflection, for example, when we talk about the ''idea'' of a person or a place. A new or an original idea can often lead to innovation. Our actions are based upon beliefs, beliefs are patterns or organized sets of ideas. Etymology The word ''idea'' comes from Greek , , , from the root of , . History An argument over the underlying nature of ideas was opened by Plato, whose exposition of his theory of forms—which recurs and accumulates ov ...