and protons trying to jazz out of each other’s way, which is what physics maintains is really taking place at your finger-tip. Or, at least, it _seems_ very different. But as we shall see, the knowledge we derive from physics is so abstract that we are not warranted in saying that what goes on in the physical world is, or is not, intrinsically very different from the events that we know through our own experiences. CHAPTER XIV PERCEPTION AND PHYSICAL CAUSAL LAWS In an earlier chapter we saw the inadequacy of the traditional notion of cause, without adequately explaining the causal laws which are a substitute in the practice of science. The time has now come when it is possible to remedy this defect, and, in so doing, to fit perception into its place in the chain of physical causation and recapitulate the main points of previous arguments. The old view was that an event A will always be followed by a certain event B, and that the problem of discovering causal laws is the problem, given an event B, of finding that event A which is its invariable antecedent or _vice versa_. At an early stage of a science this point of view is useful; it gives laws which are true usually, though probably not always, and it affords the basis for more exact laws. But it has no philosophical validity, and is superseded in science as soon as we arrive at genuine laws. Genuine laws, in advanced sciences, are practically always quantitative laws of _tendency_. I will try to illustrate by taking the simplest possible case in physics.