In
sociological jargon, this
term denotes a certain type of
idea. A
social fact is an idea that is so
universally accepted by a
population that its
objective truth becomes
irrelevant. When an idea reaches such total saturation of a population, the
pressure of the combined belief of every member thereof can often force a social fact into objective
reality,
regardless of its
existence there before its
widespread acceptance.
One excellent example is the universally accepted idea that bullies have low self-esteem. This idea was so widely accepted that educational policy was based on it and scientific research wound up taking it for granted without any proof whatsoever, since everyone just knew it was true. Recent research has shown, however that those who engage in particularly aggressive behavior are in fact those who have particularly high self-esteem but who feel threatened in that regard.
Another relevant example that demonstrates a society's need to never invalidate one of these social facts is the Catholic church's position regarding Ptolemaic astronomy. They knew it to be true so unquestionably that those who questioned it were persecuted, thereby creating pressure in favor of the truth of Ptolemaic astronomy over theories that eventually wound up having more objective truth to them.
The term was first coined by Emile Durkheim in his book, The Rules of Sociological Method