The latter term had been introduced by the physician Esquirol, who had succeeded Pinel, to refer to a form of insanity where there is a fixation or excess in only one area. It was also used widely by Étienne-Jean Georget. It was theorized to be caused by a split in the faculties of the mind. Prichard considered his first category of intellectual (rather than moral) insanity, to be equivalent to monomania. This in turn meant that the symptoms of moral insanity could increase, causing an overall degeneration into monomania. "On the surface, monomania can thus appear even more circumscribed a form of derangement than moral insanity." However, Esquirol by contrast considered moral insanity to be simply one form of monomania.