If a work contains stories that are physically impossible, it shows a defect of judgment in the author, and decreases our confidence in his other statements; but it does not follow that these others are to be rejected.  We must try to compare them with other evidence.  Even incredible stories are significant:  they show what people were capable of believing, and, therefore, under what conditions they reasoned and acted.  One cause of the incredibility of popular stories is the fusion of legend with myth.  A legend is a traditionary story about something that really happened:  it may have been greatly distorted by stupidity, or exaggeration, or dramatisation, or rationalisation, but may still retain a good deal of the original fact.  A myth, however, has not necessarily any basis of fact:  it may be a sort of primitive philosophy, an hypothesis freely invented to explain some fact in nature, such as eclipses, or to explain some social custom whose origin is forgotten, such as the sacrificing of a ram.

All historical conclusions, then, depend on a sum of convergent and conflicting probabilities in the nature of circumstantial evidence.  The best testimony is only highly probable, and it is always incomplete.  To complete the picture of any past age there is no resource but the Comparative Method.  We use this method without being aware of it, whenever we make the records of the last generation intelligible to ourselves by our own experience.  Without it nothing would be intelligible:  an ancient coin or weapon would have no meaning, were we not acquainted with the origins and uses of other coins and weapons.  Generally, the further we go back in history, the more the evidence needs interpretation and reconstruction, and the more prominent becomes the appeal to the Comparative Method.  Our aim is to construct a history of the world, and of the planet as part of the world, and of mankind as part of the life of the planet, in such a way that every event shall be consistent with, and even required by, the rest according to the principle of Causation.

CHAPTER XVIII

HYPOTHESES

Sec. 1.  An Hypothesis, sometimes employed instead of a known law, as a premise in the deductive investigation of nature, is defined by Mill as “any supposition which we make (either without actual evidence, or on evidence avowedly insufficient) in order to endeavour to deduce from it conclusions in accordance with facts which are known to be real; under the idea that if the conclusions to which the hypothesis leads are known truths, the hypothesis itself either must be, or at least is likely to be, true.”  The deduction of known truths from an hypothesis is its Verification; and when this has been accomplished in a good many cases, and there are no manifest failures, the hypothesis is often called a Theory; though this term is also used for the whole system of laws of a certain class