The works of two nineteenth century thinkers promote conflicting theories of the locus of responsibility for the course of historical events. Thomas Carlyle, in his 1841 treatise On Heroes, Hero-Worship, and the Heroic in History, places little emphasis on the events or conditions that produce major figures or the environments that allow them to rise to prominence. Instead, Carlyle posits that the extraordinary charisma, intelligence, wisdom, or political skill of individual “great” figures, invariably men, are the primary means by which social progress is effected. Herbert Spencer (1820–1903), though, writes not only that social environments are responsible for any great figures societies produce, but that Carlyle's approach is puerile and “unscientific” in the vein of many popular sociological works of the era. Although both thinkers promote a theory attempting to isolate the “mechanisms” of history vis-à-vis individual figures, only Spencer's has survived recent criticism largely intact. He emphasizes the lesser-understood contingencies of progress that comprise the immense majority of sociohistorical phenomena. He concludes that while major figures often take credit for the causal chain of significant events, the individuals themselves are less directly responsible for them than is commonly believed. This generality demonstrates how Spencer laid the foundation for twentieth-century historical scholarship, which holds to the belief that historical events, even those led by “heroes,” follow from multitudinous and sometimes untraceable social preconditions.