In looking back over a hundred years to John Stuart Mill's Principles of Political Economy and to the Communist Manifesto, joint product of Karl Marx and Frederick Engels, it is difficult not to be influenced by the stereotypes of “bourgeois” and “Marxian” economists that have developed in the process of doctrinal controversy. (It is sometimes as difficult to recognize the “orthodox” economist from the description of the “Marxian” as it is to recognize the “classical” economist from the description of the “Keynesian.”) But the difficulty does not lie simply in the probability that adherents of each school will caricature the leaders of the other, emphasizing contrasts; there is an equal probability that the modern adherents of each school will caricature their founders, emphasizing points that have come to be important. The “historical” Marx and Mill have to be sought with the special care that arises from an awareness of these difficulties.