are essential—and not even Mill professes to lay down rules for distinguishing the essential from the non-essential features of the phenomena to be investigated. The difference between scientific and primitive procedure is in this case entirely extra-logical. Again, the Method of Concomitant Variations is, as we have seen, the basis of much divination and magic; and here again the difference between the two logics is largely extra-logical. Related or similar things vary together; but what things are related or similar? The similarity which the primitive logician detects between the variations of the apparent size of the moon on the one hand, and of the actual size of sub-lunar growing or decaying objects on the other, is not regarded as essential by the man of science; and, speaking generally, we may say that is impossible to say à priori what points of similarity or dissimilarity primitive man will seize on as cardinal. And this amounts to saying that a complete history of logic from primitive times can only be written by the aid of folk-lore.
Hypothesis is another instrument of thought which is common to both stages of logic, and which is of interest to the folk-lorist. Indeed, if we accept the definition of folklore given in F.-L. J., iv, p. 196, that it is "the popular explanation of observed facts", then Hypothesis is the whole of folk-lore. But even if we limit ourselves to the statement that all popular explanations of observed facts are folk-lore (and this has the advantage of not excluding rites and customs), the importance of Hypothesis is still considerable. And here, again, the difference between savage and scientific man is not so considerable: both may accept Mill's definition that "an hypothesis is any supposition which we make in order to endeavour to deduce from it conclusions in accordance with facts which are known to be real". The principal difference lies in a difference of opinion as to the nature and necessity of verification; and with regard to primitive hypothesis as preserved in myths, we may say that it consists in explaining the thing that is
