"We must confess," said Prof. J. H. Poynting (1900, p. 616), "that physical laws have greatly fallen off in dignity. No long time ago they were quite commonly described as the Fixed Laws of Nature, and were supposed sufficient in themselves to govern the universe. Now we can only assign to them the humble rank of mere descriptions, often erroneous, of similarities which we believe we have observed.... A law of nature explains nothing, it has no governing power, it is but a descriptive formula which the careless have sometimes personified." It used to be said that "the laws of Nature are the thoughts of God"; now we say that they are the investigator's formulae summing up regularities of recurrence.[13]
If natural law aims at prediction it tells us what we can do. Moral laws, on the other hand, tell us, not what we can, but what we ought to do. The civil or municipal law, finally, tells us not what we can, nor what we ought, but what we must do. It is very evident that these three types of law may be very intimately related. We do not know what we ought to do until we know what we can do; and we certainly should consider what men can do before we pass laws prescribing what they must do. There is, moreover, no likelihood that these distinctions will ever be completely abolished. As long as the words "can," "ought," and "must" continue to have any meaning for us the distinctions that they represent will persist in science as well as in common sense.
The immense prestige which the methods of the natural sciences have gained, particularly in their application to the phenomena of the physical universe, has undoubtedly led scientific men to overestimate the importance of mere conceptual and abstract knowledge. It has led them to assume that history also must eventually become "scientific" in the sense of the natural sciences. In the meantime the vast collections of historical facts which the industry of historical students has accumulated are regarded, sometimes even by historians themselves, as a sort of raw material, the value of which can only be realized after it has been worked over into some sort of historical generalization which has the general character of scientific and ultimately, mathematical formula.