Godwin's law (or Godwin's rule of Hitler analogies) is an Internet adage that asserts that "As an online discussion grows longer, the probability of a comparison involving Hitler approaches 1"; that is, if an online discussion (regardless of topic or scope) goes on long enough, sooner or later someone will compare someone or something to Adolf Hitler or his deeds. Promulgated by the American attorney and author Mike Godwin in 1990,Godwin's law originally referred specifically to Usenet newsgroup discussions. It is now applied to any threaded online discussion, such as Internet forums, chat rooms, and comment threads, as well as to speeches, articles, and other rhetoric where reductio ad Hitlerum occurs.
Generalization, corollaries, usage
With respect to probability theory, Godwin's law becomes a special case of a Bernoulli trial.
Indeed, there are many corollaries to Godwin's law, some considered more canonical (by being adopted by Godwin himself) than others. For example, there is a tradition in many newsgroups and other Internet discussion forums that once such a comparison is made, the thread is finished and whoever mentioned Adolf Hitler has automatically lost whatever debate was in progress