This ultimate term or ground of knowledge is always of a metaphysical character. It is something in the way of a preconception, accepted uncritically, but applied in criticism and demonstration of all else with which the science is concerned. So soon as it comes to be criticised, it is in a way to be superseded by a new, more or less altered formulation; for criticism of it means that it is no longer fit to survive unaltered in the altered complex of habits of thought to which it is called upon to serve as fundamental principle. It is subject to natural selection and selective adaptation, as are other conventions. The underlying metaphysics of scientific research and purpose, therefore, changes gradually and, of course, incompletely, much as is the case with the metaphysics underlying the common law and the schedule of civil rights. As in the legal framework the now avowedly useless and meaningless preconceptions of status and caste and precedent are even yet at the most metamorphosed and obsolescent rather than overpassed,--witness the facts of inheritance, vested interests, the outlawry of debts through lapse of time, the competence of the State to coerce individuals into support of a given policy,--so in the science the living generation has not seen an abrupt and traceless disappearance of the metaphysics that fixed the point of view of the early classical political economy. This is true even for those groups of economists who have most incontinently protested against the absurdity of the classical doctrines and methods. In Professor Marshall's words, "There has been no real breach of continuity in the development of the science." But, while there has been no breach, there has none the less been change,--more far-reaching change than some of us are glad to recognise; for who would not be glad to read his own modern views into the convincing words of the great masters? Seen through modern eyes and without effort to turn past gains to modern account, the metaphysical or preconceptional furniture of political economy as it stood about the middle of this century may come to look quite curious. The two main canons of truth on which the science proceeded, and with which the inquiry is here concerned, were: (_a_) a hedonistic-associational psychology, and (_b_) an uncritical conviction that there is a meliorative trend in the course of events, apart from the conscious ends of the individual members of the community. This axiom of a meliorative developmental trend fell into shape as a belief in an organic or quasi-organic (physiological)[2] life process on the part of the economic community or of the nation; and this belief carried with it something of a constraining sense of self-realising cycles of growth, maturity and decay in the life history of nations or communities.