Historically, cyclothymia has been used broadly to refer either to a temperament (Kretschmer) or the entire range of bipolar disorders. Within this spectrum, it is uncertain whether it characterizes the "hard" (or manic-depressive) forms (as Kurt Schneider argued) or its "soft" expressions (bipolar II and highly recurrent depressions); the latter perspective is in line with Falret's view that the melancholic expressions of his folie circulaire (circular insanity) were highly prevalent in the community.