"W. T. Krug follows Kant's usage in identifying solipsism with moral egoism ('making one's own self the end of all one's actions')... This identification is still repeated as late as 1890 by F. Kirchner. Meanwhile, some time during the 19th cent., solipsism was transferred from moral or practical egoism to theoretical (either epistemological or metaphysical) egoism, i.e. to the theory that I can know nothing but my own ideas and that I and my ideas are all that exists. This view was called simply 'egoism' by Wolf (who treats it, rightly, as an extreme species of idealism), Mendelssohn, Tetens, and other 18th cent. writers."