There is a great difference between historical facts and speculative opinions; nor is the knowledge of the one propagated in the same manner with that of the other. An historical fact, while it passes by oral tradition from eye-witnesses and contemporaries, is disguised in every successive narration, and may at last retain but very small, if any, resemblance of the original truth, on which it was founded. The frail memories of men, their love of exaggeration, their supine carelessness; these principles, if not corrected by books and writing, soon pervert the account of historical events; where argument or reasoning has little or no place, nor can ever recal the truth, which has once escaped those narrations. It is thus the fables of HERCULES, THESEUS, BACCHUS are supposed to have been originally founded in true history, corrupted by tradition. But with regard to speculative opinions, the case is far otherwise.
If these opinions be founded on arguments so clear and obvious as to carry conviction with the generality of mankind, the same arguments, which at first diffused the opinions, will still preserve them in their original purity. If the arguments be more abstruse, and more remote from vulgar apprehension, the opinions will always be confined to a few persons; and as soon as men leave the contemplation of the arguments, the opinions will immediately be lost and be buried in oblivion. Whichever side of this dilemma we take, it must appear impossible, that theism could, from reasoning, have been the primary religion of human race, and have afterwards, by its corruption, given birth to polytheism and to all the various superstitions of the heathen world. Reason, when obvious, prevents these corruptions: When abstruse, it keeps the principles entirely from the knowledge of the vulgar, who are alone liable to corrupt any principle or opinion.
~ David Hume, The Natural History of Religion, 1757