The knowledge of the laws of evolution in the past would have no value for Marxists unless this knowledge could help them to predict the future. Such foreknowledge is supposed to give the Marxist doctrine of the class struggle the aureole of scientific certainty, and to reinforce the confidence of the masses in Marxist guidance because it makes them believe that ultimate victory is indubitable. In view of the impossibility of basing foreknowledge on any historical method, Marxism gets out of the difficulty with the aid of determination by economic categories. Marxism, in its causal interpretation of history, confounds causes and conditions in the same way in which Darwinism has confounded them in biology. Darwin’s discovery led Darwinists to believe that the Darwinian theory had explained why animal species undergo transformation.