in philosophy, formerly, moral egoism (as used in the writings of Immanuel Kant), but now, in an epistemological sense, the extreme form of subjective idealism that denies that the human mind has any valid ground for believing in the existence of anything but itself. The British idealist F.H. Bradley (Bradley, F H), in Appearance and Reality (1897), characterized the solipsistic view as follows:

Presented as a solution of the problem of explaining human knowledge of the external world, it is generally regarded as a reductio ad absurdum. The only scholar who seems to have been a coherent radical solipsist is Claude Brunet, a 17th-century French physician.