Since Rousseau and Kant, there have been two schools of Liberalism, which may be distinguished as the hard-headed and the soft-hearted. The hard-headed developed, through Bentham, Ricardo, and Marx, by logical stages into Stalin; the soft-hearted, by other logical stages, through Fichte, Byron, Carlyle, and Nietzsche, into Hitler. That statement, of course, is too schematic to be quite true, but it may serve as a map and a mnemonic. The stages in the evolution of ideas have had almost the quality of the Hegelian dialectic: doctrines have developed, by steps that each seem natural, into their opposites. But the developments have not been due solely to the inherent movement of ideas; they have been governed, throughout, by external circumstances and the reflection of these circumstances in human emotions. … That this is the case may be made evident by one outstanding fact: that the ideas of liberalism have undergone no part of this development in America, where they remain to this day as in Locke.

Bertrand Russell, History of Western Philosop…, loc. 2337