It is of course manifest that, so understood, the mechanical view of physical processes is forced upon us by our practical needs wherever it is requisite to formulate rules for successful intervention in the course of nature. If we are to intervene with success in the course of events, that course must, as we have already seen, be capable of being regarded as approximately uniform, otherwise we can have no security that our intervention according to rule and precedent will have a uniform and unambiguous result. Hence, if we are to formulate general rules for practical intervention, we must be able to treat the course of things as—to all intents and purposes—mechanical. And, on the contrary, if there are processes which cannot be even approximately regarded as mechanical, our power of framing general rules for the practical manipulation of events cannot extend to those processes. The limits of the mechanical view of events are likewise the limits of empirical science and of the general precepts of the practical arts. We see this admirably exemplified in the study of human natures. The behaviour of large aggregates of human beings, as we have already learned, exhibits approximate uniformity, at least in many respects, and may thus be treated as to all intents and purposes mechanical in those respects. Hence it is possible to have a number of empirical sciences of human nature, such as Ethnology and Sociology, in which those uniformities are collected and codified, and to base on these sciences a number of general prudential maxims for the regulation of our behaviour towards our fellow-men considered in the abstract. But when we come to deal with the actual conduct of concrete human individuals, the mechanical view, as we have seen, fails us. What a concrete individual will do can only be inferred with certainty from the knowledge of his interests and purposes; there can thus be no general science of individual character, and consequently no general rules of prudence for behaviour towards an individual fellow-man. It is not to the so-called sciences of human nature, but to personal experience of the individual himself, we have to go for the knowledge how to regulate our conduct towards the actual individuals with whom life brings us into direct and intimate personal relation. Philosophical reflection upon the nature and limits of scientific knowledge fully confirms the verdict passed by the practical sense of mankind on the doctrinaire pedantry which seeks to deduce rules for dealing with actual individuals from anything but concrete understanding of individual character and purpose.