Gustav A. Köttgen um 1846 · Public domain

A German-Jewish philosopher who moved from being an early influence on Karl Marx and Friedrich Engels — developing an "ethical socialism" and theory of alienation before either of them — to becoming, in his later years, an early forerunner of Zionism. Disillusioned by the resurgence of nationalism and antisemitism after 1848, he argued in his 1862 book Rome and Jerusalem that Jews were a distinct nation whose future depended on a national revival in their historical homeland, anticipating political Zionism by decades.