MENTAL SYSTEMS 55
stands, and is used for pulling the train. A third is a pro fessor of economics ; to him also it is a complicated organiza tion of parts and functions (dimly understood for the most part), the invention of which occurred at a particular point in economic history and which has performed a most im portant function in the economic development of society. The latter associations may be in the focus of his attention, or only in the fringe, and so may constitute only a surround ing nebula of meaning. In either case they distinguish the meaning in his mind from that in the others. But to him also the engine is something that pulls the train. In this last point all the meanings, so divergent in other respects, agree, because that is the one aspect of the engine which is most obvious and most manifestly affects the daily lives of men. We may say, then, that the use meanings of things are like threads that run through variant mental systems, giving them unity; and when these use meanings are of an obvious, every-day character, the larger is the number of mental systems which they unite and the more closely the systems are united. On the other hand, those meanings which are constituted in the effort to systematize one s knowledge reflectively will become more and more unlike in different minds the more general, abstract, theoretical they become.
This divergence of mental systems in their theoretical meanings is to a limited extent overcome by the precision given to technical terms. A technical term is a coin of the realm which passes at its face value among all the in habitants. It is supposed to mean the same thing in every mind; and it approximates this generality of meaning as nearly as is possible. But in every mind these terms of fixed meaning are organized into larger bodies of ideas, and, in these larger correlations of thought, acquire quite different atmospheres of meaning. When, therefore, the effort is made by means of carefully framed definitions to reduce a number of minds to a common denominator in their thought upon some subject, only partial success can be expected.
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