in some tenable fashion construed any apparent exception as a special instance under the rule. So also in modern scientific inquiry. The conceptual elements with which the scientist is content to work are precisely those that have commended themselves as competent in their technological use. Since action by contact is, on the whole, the working principle in the machine process, it is also accepted as the prime postulate in the formulation of all exact knowledge of impersonal facts. There is, of course, no inclination here to criticise or take exception to this characteristic habit of thought that pervades modern scientific inquiry. It has done good service, and to this generation, trained in the enexorably efficient ways of the machine process, the fact that it works is conclusive of its truth.[148] Yet the further fact is not to be overlooked that adherence to this principle is not due to unsophisticated observation simply. It is a principle, a habit of thought, not a fact of simple observation. Doubtless it is a fact of observation, direct and unambiguous, in respect of our own manual operations; and doubtless also it is a matter of such ready inference in respect of many external phenomena as to do duty as a fact of observation in good faith; but doubtless also there are many of these external phenomena that have to be somewhat painstakingly construed to bring them under the rule. Conceivably, even if such a habit of thought had not been handed down from the experience of handicraft it might have been induced by the discipline of the machine process, and might even have been ingrained in men exposed to this discipline in sufficiently rigorous fashion to serve as a prime postulate of scientific inquiry; the machine process doubtless bears out such a principle in the main, and very rigorously. But in point of historical fact it is quite unnecessary to suppose this principle of action by contact to be a product _de novo_ of the discipline of the machine, since it is older than the advent of the machine industry and is also quite consonant with the habits of work enforced by the technology of handicraft, more so indeed than with the technology of the machine industry. It appears fairly indubitable that this principle is a legacy taken over from the experience of life in the days of craftsmanship. And it may even be an open question whether the machine technology would not today be of an appreciably different complexion if it had, as it conceivably might have, developed without the hard and fast limitations imposed by this postulate. Doubtless, scientific inquiry, and the theoretical formulations reached by such inquiry, would differ somewhat notably from what they currently are if the scientists had gone to their work without such a postulate, or holding it in a qualified sense, as a principle of limited scope, as applying only within a limited range of phenomena, only so far as empirical evidence might enforce it in detail.