Page:An Enquiry Concerning the Principles of Natural Knowledge.djvu/199



Evidently therefore causal characters can only be directly known to us as functions of apparent characters. They are characters of characters. For example, a quantity which we assign to a physical object as the result of some measurement is a character of its apparent character.

61.2 It is necessary however to avoid a misunderstanding; the causal character of an event is not merely a function of the apparent character of that event. It is in truth a function of the apparent characters of all events, though in general the apparent character of that event — or of an associated event of somewhat later date — is the dominant element in the formation of the function. For example, a quantity determined by measurement is a relation of the apparent character of the event to the apparent characters of other events. But it is the dominance of the apparent character which in practice makes the discovery of the causal character generally possible; for it assigns the situation of the causal character. This dominance is merely a practical aid to the discovery of causal characters and has in it no element of necessity. Indeed as causal characters are progressively discovered, scientific theory assigns causal characters to events which are destitute of, apparent character — namely the events forming the ether in empty space and time.

61.3 So far the explanation of causal characters has exhibited them as the outcome and issue from apparent characters, whereas the causal idea, which is that of science, requires the causal characters should be the origin of the apparent characters. We have to seek the reason for this inversion of ideas.

Causal characters are much simpler than apparent