Now all of this is, of course, commonplace. And yet a failure to recognize it has vitiated very much thinking in the field of economic theory. Economic thought is to-day very largely based on the philosophic conceptions which characterize the period in which economics began to be a differentiated science,--the skeptical doctrines of David Hume, the close friend of Adam Smith.[88] The individual is all-important; his world of thought and feeling is shut off from that of every other man; social relationships are largely mechanical, and grow out of calculating self-interest on the part of the individual; social laws are conceived after the analogy of physical laws. Ethics and politics, however, have been far more influenced by later thinking, and the organic conception of society has largely dominated these sciences of late, while the new science, sociology, free to base itself more largely upon present-day epistemological, philosophical, and psychological notions, has gone further than any other in accepting the doctrine of the unity and pervasiveness of social relations, organically conceived. I think there are few things more strikingly in contrast than the conception of society which the student meets in most works on economic theory, and that which he meets in studying the other social sciences. That this is so is due precisely to the fact that the economists have too largely neglected philosophy and psychology, and have accepted uncritically the assumptions of the founders of the science. Doctrines accepted then have become _crystallized_, and still form part of the current stock in trade of economic science, even though rejected by philosophy itself. To one of these faulty doctrines from the earlier time, attention has already been called. It is that the intensities of wants and aversions in the mind of one man stand in no relation to the same phenomena in the mind of another man, and that there can be no comparison instituted between them. The individual is an isolated monad,[89] mechanically connected with his fellows, who are to him "a part of the _non-ego_,"[90] but spiritually self-sufficient and inaccessible. The doctrine appears in Marshall's statement:[91] "No one can compare and measure accurately against one another even his own mental states at different times, and no one can measure the mental states of another at all, except indirectly and conjecturally, by their effects." Pareto I have quoted, as also Jevons, in chapter IV. The doctrine appears in Professor Veblen's recent article in criticism of Professor Clark:[92]--