THE SIMILARITY OF TALES
The argument that myths tend to be alike, because there is a common source to them (Frazer's argument), is often an assumption brought to myths, not a deduction based on evidence.
"Poems and poetic tales tend to be a little alike, not because Hebrews were really Chaldeans, nor because Christians were really Pagans, but because men are really men. Because there is, in spite of all the trend of modern thought, such a thing as man and the brotherhood of men. Anyone who has really looked at the moon might have called the moon a virgin and a huntress without ever having heard of Diana. Anyone who had ever looked at the sun might call it the god of oracles and of healing without having heard of Apollo. A man in love, walking about in a garden, compares a woman to a flower, and not to an earwig; though an earwig also was made by God, and has many superiorities to flowers in point of education and travel. To hear some people talk, one would think that the love of flowers had been imposed by some long priestly tradition, and the love of earwigs forbidden by some fearful tribal taboo."
THE FALLACY OF BORROWING AS A COMPLETE EXPANATION
The second argument he tackes is that when there is borrowing, it is using it in the same way, rather than taking inspiration and a starting point with the stories. Frazer supposed that if there was borrowing of stories, this meant that they were taken across completely, and thought this discredited the borrower; what philosophers (and linguists) now call the "genetic fallacy".
"The second great blunder is to suppose that such fables, even when they really are borrowed from older sources, are used in an old tired and customary spirit....Thus, when professors tell us that the Christians "borrowed" this or that fable or monster from the heathens, it is as if people said that a bricklayer had "borrowed" his bricks from clay, or a chemist had "borrowed" his explosives from chemicals; or that the Gothic builders of Lincoln or Beauvais had "borrowed" the pointed arch from the thin lattices of the Moors."
