Epistemology is the main discipline studying declarative knowledge. Among other things, it studies the essential components of declarative knowledge. According to a traditionally influential view, it has three elements: it is a belief that is true and justified. As a belief, it is a subjective commitment to the accuracy of the believed claim while truth is an objective aspect. To be justified, a belief has to be rational by being based on good reasons. This means that mere guesses do not amount to knowledge even if they are true. In contemporary epistemology, additional or alternative components have been suggested. One proposal is that no contradicting evidence is present. Other suggestions are that the belief was caused by a reliable cognitive process and that the belief is infallible.


Types of declarative knowledge can be distinguished based on the source of knowledge, the type of claim that is known, and how certain the knowledge is. A central contrast is between a posteriori knowledge, which arises from experience, and a priori knowledge, which is grounded in pure rational reflection. Other classifications include domain-specific knowledge and general knowledge, knowledge of facts, concepts, and principles as well as explicit and implicit knowledge.


Declarative knowledge is often contrasted with practical knowledge and knowledge by acquaintance. Practical knowledge consists of skills, like knowing how to ride a horse. It is a form of non-intellectual knowledge since it does not need to involve true beliefs. Knowledge by acquaintance is a familiarity with something based on first-hand experience, like knowing the taste of chocolate. This familiarity can be present even if the person does not possess any factual information about the object. Some theorists also contrast declarative knowledge with conditional knowledge, prescriptive knowledge, structural knowledge, case knowledge, and strategic knowledge.


Declarative knowledge is required for various activities, such as labeling phenomena as well as describing and explaining them. It can guide the processes of problem-solving and decision-making. In many cases, its value is based on its usefulness in achieving one's goals. However, its usefulness is not always obvious and not all instances of declarative knowledge are valuable. A lot of knowledge taught at school is declarative knowledge. It is said to be stored as explicit memory and can be learned through rote memorization of isolated, singular, facts. But in many cases, it is advantageous to foster a deeper understanding that integrates the new information into wider structures and connects it to pre-existing knowledge. Sources of declarative knowledge are perception, introspection, memory, reasoning, and testimony.

Types[edit]

Declarative knowledge arises in many forms. It is possible to distinguish between them based on the type of content of what is known. For example, empirical knowledge is knowledge of observable facts while conceptual knowledge is an understanding of general categorizations and theories as well as the relations between them.^[62][63][64] Other examples are ethical, religious, scientific, mathematical, and logical knowledge as well as self-knowledge. A further distinction focuses on the mode of how something is known. On a causal level, different sources of knowledge correspond to different types of declarative knowledge. Examples are knowledge through perception, introspection, memory, reasoning, and testimony.^[62][65][66]


On a logical level, forms of knowledge can be distinguished based on how a knowledge claim is supported by its premises. This classification corresponds to the different forms of logical reasoning, such as deductive and inductive reasoning.^[62][67][68] A closely related categorization focuses on the strength of the source of the justification. It distinguishes between probabilistic and apodictic knowledge. The distinction between a priori and a posteriori knowledge, on the other hand, focuses on the type of the source. These classifications overlap with each other at various points. For example, a priori knowledge is closely connected to apodictic, conceptual, deductive, and logical knowledge. A posteriori knowledge, on the other hand, is linked to probabilistic, empirical, inductive, and scientific knowledge. Self-knowledge may be identified with introspective knowledge.^[62][69]


The distinction between a priori and a posteriori knowledge is determined by the role of experience and matches the contrast between empirical and non-empirical knowledge. A posteriori knowledge is knowledge from experience. This means that experience, like regular perception, is responsible for its formation and justification. Knowing that the door of one's house is green is one example of a posteriori knowledge since some form of sensory observation is required. For a priori knowledge, on the other hand, no experience is required. It is based on pure rational reflection and can neither be verified nor falsified through experience. Examples are knowing that 7 + 5 = 12 or that whatever is red everywhere is not blue everywhere.^[70] In this context, experience means primarily sensory observation but can also include related processes, like introspection and memory. However, it does not include all conscious phenomena. For example, having a rational insight into the solution of a mathematical problem does not mean that the resulting knowledge is a posteriori. And knowing that 7 + 5 = 12 is a priori knowledge even though some form of consciousness is involved in learning what symbols like "7" and "+" mean and in becoming aware of the associated concepts.^[71][72][69]


One classification distinguishes between knowledge of facts, concepts, and principles. Knowledge of facts pertains to the association of concrete information, for example, that the red color on a traffic light means stop or that Christopher Columbus sailed in 1492 from Spain to America. Knowledge of concepts applies to more abstract and general ideas that group together many individual phenomena. For example, knowledge of the concept of jogging implies knowing how it differs from walking and running as well as being able to apply this concept to concrete cases. Knowledge of principles is an awareness of general patterns of cause and effect, including rules of thumb. It is a form of understanding how things work and being aware of the explanation of why something happened the way it did. Examples are that if there is lightning then there will be thunder or if a person robs a bank then they may go to jail.^[73][74] Similar classifications distinguish between declarative knowledge of persons, events, principles, maxims, and norms.^[75][76][77]


Declarative knowledge is traditionally identified with explicit knowledge and contrasted with tacit or implicit knowledge. Explicit knowledge is knowledge of which the person is aware and which can be articulated. It is stored in explicit memory. Implicit knowledge, on the other hand, is a form of embodied knowledge that the person cannot articulate. The traditional association of declarative knowledge with explicit knowledge is not always accepted in the contemporary literature. Some theorists argue that there are forms of implicit declarative knowledge. A putative example is a person who has learned a concept and is now able to correctly classify objects according to this concept even though they are not able to provide a verbal rationale for their decision.^[78][79][80]


A further contrast is between domain-specific and general knowledge. Domain-specific knowledge applies to a narrow subject or a particular task but is useless outside this focus. General knowledge, on the other hand, concerns wide topics or has general applications. For example, declarative knowledge of the rules of grammar belongs to general knowledge while having memorized the lines of the poem The Raven is domain-specific knowledge. This distinction is based on a continuum of cases that are more or less general without a clear-cut line between the types.^[6][81] According to Paul Kurtz, there are six types of descriptive knowledge: knowledge of available means, of consequences, of particular facts, of general causal laws, of established values, and of basic needs.^[82] Another classification distinguishes between structural knowledge and perceptual knowledge.^[83]

Value[edit]

Declarative knowledge plays a central role in human understanding of the world. It underlies activities such as labeling phenomena, describing them, explaining them, and communicating with others about them.^[100] The value of declarative knowledge depends in part on its usefulness in helping people achieve their objectives. For example, to treat a disease, knowledge of its symptoms and possible cures is beneficial. Or if a person has applied for a new job then knowing where and when the interview takes place is important.^{[101][102][103]} Due to its context-independence, declarative knowledge can be used for a great variety of tasks and because of its compact nature, it can be easily stored and retrieved.^[4][3] Declarative knowledge can be useful for procedural knowledge, for example, by knowing the list of steps needed to execute a skill. It also has a key role in understanding and solving problems and can guide the process of decision-making.^{[104][105][106]} A related issue in the field of epistemology concerns the question of whether declarative knowledge is more valuable than true belief. This is not obvious since, for many purposes, true belief is as useful as knowledge to achieve one's goals.^{[103][107][108]}


Declarative knowledge is primarily desired in cases where it is immediately useful.^[97] But not all forms of knowledge are useful. For example, indiscriminately memorizing phone numbers found in a foreign phone book is unlikely to result in useful declarative knowledge.^[102] However, it is often difficult to assess the value of knowledge if one does not foresee a situation where it would be useful. In this regard, it can happen that the value of apparently useless knowledge is only discovered much later. For example, Maxwell's equations linking magnetism to electricity were considered useless at the time of discovery until experimental scientists discovered how to detect electromagnetic waves.^[97] Occasionally, knowledge may have a negative value, for example, when it hinders someone to do what would be needed because their knowledge of associated dangers paralyzes them.^[102]