Our two outside perspectives on myth and religion are, unlike the theological, thoroughly secular. When at their purest, history and comparative religion neither require nor tolerate viewing their objects with sacral eyes.
Otherwise, there is a distinct difference between the two.
History wants to know what religious events—such as foundings, political intrigues, and schisms—have occurred, in what chronological order they appeared, and, often as not, why they happened.
Comparative Religion tries to locate and analyze the similarities and differences of themes, myths, social structures, practices, and ideas that are found in the religions of the world, great or small, archaic or modern. Instead of viewing single events in their particularity, it seeks patterns that have appeared throughout human history.
Going beyond these catalogue copy definitions, we may say that the history of religions will use historical methods to ask when a text was produced, by whom, within what cultural context, and from what other texts, in order to ferret out the original meaning of that text. And comparative religion will examine such things as creation myths, rituals, beliefs, and so on, in order to see what they have in common and how they differ.
Both perspectives can ask why these patterns occur. For a moment, let’s wonder why both Buddhism and Christianity, among other religions, have founder myths. Did the miracle-filled stories about Gotama’s life influence the stories about Jesus, as a purely historical investigation might theorize? Or is there some universal archetype that underlies all hero myths, as Joseph Campbell claimed?
There appears to be an analogy between biological life and religion. Think, say, of the variety of turtle species that are found throughout the world. Species of the order Testudines are found on every continent except Antarctica, on many islands, and in the oceans. They’ve been around for the last 215 million years.
Now, think of the variety of creation myths. From tribal societies to the American present, these stories continue to be recited. They, too, are found everywhere on the inhabited earth, though their appearance has been relatively recent.
This analogy might be more than coincidence. Just as the fact that biological commonality and diversity are determined by both genetics and circumstance, it may be that religious commonality and diversity are determined by the same factors.
But so far, that’s speculation.