Defining something as common knowledge can differ based on circumstances because there are variations in what is considered common knowledge amongst different groups.
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 is the capital of
France." 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 and
bleach." 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 ==