Many of the problems we saw arising in connection with the principle of simplicity are relevant to the principle of connectivity problems which will be discussed in this chapter. Here, too, the question arises whether the principle is an assertion about the nature of the physical universe or an assertion about something else. If it is an assertion about the world, then it has to be specified what would constitute a violation of the principle and to be shown that no such instance has ever been presented by nature. If, on the other hand, the principle is not an empirical assertion, then we shall want to inquire what sort of statement is being made. What are the reasons given for adopting it? And again, of course, the most important problem is to ascertain the precise meaning of the concept of 'connectivity' and to describe the exact circumstances in which the principle of connectivity applies. Needless to say, just as before,
To begin with I shall try to give a crude idea of what this principle is about, a description which for the time being will take a minimal and innocuous form, and with which most people would, I think, agree. Moreover, since the principle of connectivity is really an extension of the principle of causality, it will therefore be helpful to approach the idea of connectivity through the much better notion of causality. The principle of causality will serve as a familiar background to which our principle can conveniently be contrasted.