A more subtle enemy of revolutionary science than its open rejection, or the attempt to destroy it by “revision”, is the Menshevik betrayal of it. I have already shown that the distinction between Menshevik and Bolshevik can only be defined psychologically, and that Lenin originally so defined it. It seems to me of great importance, not only to revolutionary science, but to human wisdom in general, that this distinction should be really understood. It does not belong merely to politics, but can be made wherever human beings gather together on the basis of belief in a radical or extreme idea.