Represented mainly by
Karl Marx; also by his
anarchist rivals,
Kropotkin and
Bakunin. All sought to distinguish their particular brands of
Socialism from that of their precedessors, those who adhered to
Utopian Socialism.
Not a
contradiction in terms. Socialism has been accorded scientific treatment by everyone from
Marx to
Marcuse; it is only when
Marx makes prophecies that
Marxism becomes unscientific. Scientific, by which I mean grounded on a rigorous system of analysis and not mere "moralizing." By the standards of 20th century empirical science, I'm sure any sort of "premodern" science looks quite sloppy indeed. In addition, Marx's science can be wildly inaccurate; as can any old science be --
Darwinism, for example.
Marxian economics is fairly sound, although there a some problems relating to the
Labor Theory of Value (which
Marx shared with
Smith and
Ricardo) that have not been worked out yet.
Socialism can be as scientific as
capitalism; although there are limitations on how scientific
economics and
sociology can be. (
Remember kids, they're only
pseudo-sciences.)