The history of the description by Jean-Pierre Falret of circular insanity, the origin of our present day bipolar disorder, is presented as well as the claims of priority raised by his colleague Jules Baillarger. A detailed account is given of the long-lasting controversy which has often given rise to biased judgments about the respective roles of the two psychiatrists. It is shown that the clinical concept was an expression of Falret's views about the nature of mental disorders and that, through the influence these views had on future nosological systems, the apparently purely picturesque episode corresponds to a landmark in the history of psychiatry.