To begin with, it is clear that the undeviating conformity of the actual course of any concrete process to scientific “law” cannot be verified as an empirical fact by observation or experiment. For in no observation or experiment can we ever deal with the whole of any concrete actual event or process. We have always, for the purposes of our observation, to select certain of the general aspects of the process, to which we attend as the “relevant factors” or “conditions” of the result, while we disregard other aspects as “immaterial” or “accidental” circumstances. And this artificial abstraction, as we saw in discussing Causality, though indispensable for our practical purposes, is logically indefensible. Again, within the aspects selected for attention, all that experiment can establish is that the deviation from uniform law, if there is any deviation, is not sufficiently great to affect our measurements and calculations. But how far our standards of measurement are from rigid precision may be readily learned from the chapter on physical standards in any good work on the logic of the inductive sciences.[131] Our failure to detect deviation from law is absolutely worthless as evidence that no deviation has taken place. Thus, if the absolute uniformity of natural processes is more than a practical postulate, it must be an axiom, that is, it must be implied in the very notion of those processes as elements in a systematic whole. But it should at once be clear that we have no more ground for asserting such uniformity as an axiom, than we had for treating the causal postulate as axiomatic. It is by no means implied in the concept of a systematic whole that its parts shall be connected by uniform law. For the unity of the system may be teleological, that is, the parts may be connected by the fact that they work together to realise the same end, to execute the same function. In that case the behaviour of any one part will depend on the demands laid upon it by the plan which the working of the system fulfils. As these demands vary from time to time, the behaviour of the part under consideration will then vary correspondingly, though to all appearance its surroundings may, for a spectator who fails to grasp the end or purpose realised by the system, be identical.[132] This is actually the case with those systematic wholes in which human insight can directly detect unity of purpose or aim. A man with definite purposes before him does not react in a uniformly identical way upon situations which, apart from their relation to his purpose, would be pronounced identical. He learns, for instance, from previous failure in the same circumstances, and so acquires the power to react on them in a way better adapted to the obtaining of his end. Or his progressive execution of his purpose, where there has been no failure, may require different conduct on the two occasions. To speak with strict logical accuracy, the situations, relatively to his special