And according to both the Collins Gem English Dictionary (New Edition for the 21st Century) and the Oxford Dictionary of Current English (Third Edition), "God" and "the Devil" are to be capitalized, presumably because they are the names of beings, just like "Zeus" is, but "heaven" and "hell" are, in fact, lowercase. Furthermore, in my psychology text book on death and dying, entitled, "The Last Dance: Encountering Death and Dying (Eighth Edition)" "Purgatory" is capitalized (as there is only one Purgatory), whereas "heaven" and "hell" are lowercase. This all makes perfect sense to me in accordance with the argument that I have given above.

How does there only being one heaven and hell mean that they should be lowercase? How do you logically go from the former claim to the latter one? I don't understand. And that's not true, by the way; there are different variations of heaven and hell in the many different myths that humanity has come up with throughout history, Christianity only being one of them. In a way, you could say that there are many "heavens" and "hells" that you can find in mythology, which would actually be good reason for them to be lowercase, since, in that case, they would NOT be proper nouns. For example, Valhalla is just one version of heaven, hence making heaven like "city" or "country." Buddhism has its heaven: Nirvana. Now take a look at this statement: "There is no heaven or hell awaiting you when you die." In that sentence, it is being stated that no heaven or hell of any kind exist, making them both common nouns. And most biblical translations do, in fact, have "heaven" and "hell" as being lowercase.