Common knowledge is

knowledge Knowledge is an Declarative knowledge, awareness of facts, a Knowledge by acquaintance, familiarity with individuals and situations, or a Procedural knowledge, practical skill. Knowledge of facts, also called propositional knowledge, is oft ...

that is publicly known by everyone or nearly everyone, usually with reference to the

community A community is a social unit (a group of people) with a shared socially-significant characteristic, such as place, set of norms, culture, religion, values, customs, or identity. Communities may share a sense of place situated in a given g ...

in which the knowledge is referenced. Common knowledge can be about a broad range of subjects, such as science,

literature Literature is any collection of Writing, written work, but it is also used more narrowly for writings specifically considered to be an art form, especially novels, Play (theatre), plays, and poetry, poems. It includes both print and Electroni ...

, history, or

entertainment Entertainment is a form of activity that holds the attention and Interest (emotion), interest of an audience or gives pleasure and delight. It can be an idea or a task, but it is more likely to be one of the activities or events that have deve ...

. Since individuals often have different knowledge bases, common knowledge can vary and it may sometimes take large-scale studies to know for certain what is common knowledge amongst large groups of people. Often, common knowledge does not need to be cited. Common knowledge is distinct from

general knowledge General knowledge is information that has been accumulated over time through various media and sources. It excludes specialized learning that can only be obtained with extensive training and information confined to a single medium. General know ...

. In broader terms, common knowledge is used to refer to information that an agent would accept as valid, such as information that multiple users may know. Assigning something the label of common knowledge requires certain considerations about the involved community, group, society and/or individuals, the time period, and the location.

Variation

Defining something as common knowledge can differ based on circumstances because there are variations in what is considered common knowledge amongst different groups. The variation can come from the time period, culture, population, class, age, demographic, and other circumstances. For example, the

Fifth Amendment to the United States Constitution The Fifth Amendment (Amendment V) to the United States Constitution creates several constitutional rights, limiting governmental powers focusing on United States constitutional criminal procedure, criminal procedures. It was ratified, along with ...

might be considered common knowledge among people residing in the United States of a certain age, but cannot be considered common knowledge when considering the general population of other countries.

Instability

Common knowledge is not always stable, and can shift over time to create new common knowledge. Knowledge that was once considered common knowledge amongst a group, society, or community might later become known as false. For example, for centuries it was common knowledge in Europe that the Sun revolved around the Earth, but after years of arguments, it is now common knowledge that the Earth revolves around the Sun.

Large scale

On a larger global scale, it is not possible to define almost any knowledge as common knowledge because it is difficult to know how far a fact has spread in global populations without large-scale global population studies. For example, the current president of the United States might be considered common knowledge in much of the world because of the power associated with that position, but one cannot assume that there is global recognition of this fact as common knowledge without further research into the knowledge of global populations.

Common belief

It is hard to distinguish fact from belief and thus there are scholars who prefer to separate common knowledge from common belief. Common belief is something that is more easily defined because the requirement is only that a majority of people within a specific group, community, or society believe something to be true whereas common knowledge must meet this requirement and also prove that the belief is a fact.

Examples

* "

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

is the capital of

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

." Many capital cities of developed countries are considered common knowledge by most people, but one cannot claim this as common knowledge for global populations without further research. * "It is dangerous to mix

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

and

bleach Bleach is the generic name for any chemical product that is used industrially or domestically to remove color from (i.e. to whiten) fabric or fiber (in a process called bleaching) or to disinfect after cleaning. It often refers specifically t ...

." Though both common household chemicals, accidents involving the mixing of ammonia and bleach are rare, because the potentially lethal danger in their chemical reaction is a widely circulated cautionary tale amongst some American families and so could possibly be considered common knowledge in those populations, but may not extend to wider populations.

Other settings

Many techniques have been developed in response to the question of distinguishing truth from fact in matters that have become "common knowledge". Techniques for how to shape common knowledge can vary through professional settings.

Legal

In legal settings,

rules of evidence The law of evidence, also known as the rules of evidence, encompasses the rules and legal principles that govern the proof of facts in a legal proceeding. These rules determine what evidence must or must not be considered by the trier of fa ...

generally exclude

hearsay Hearsay, in a legal forum, is an out-of-court statement which is being offered in court for the truth of what was asserted. In most courts, hearsay evidence is Inadmissible evidence, inadmissible (the "hearsay evidence rule") unless an exception ...

, which may draw on "facts" someone believes to be "common knowledge". The use of common knowledge in law varies between countries.

References

{{DEFAULTSORT:Common Knowledge Consensus reality Sociology of knowledge Social epistemology Consensus Concepts in epistemology