This might be the trickiest theme of them all. "Thanatopsis" doesn’t talk directly about any kind of religion. Still, the idea of death is all tied up in questions of spirituality. It’s like an undercurrent in this poem, rarely out in the open, but always there. What happens to us after we die? Does the soul live on? Those are definitely spiritual questions, and even if the poem doesn’t address them directly, they are still definitely in play.
In spite of the comforting tone of the final line, the poem mostly directs our attention away from spiritual concerns. Instead, it attempts to reassure us by focusing our attention on the ordinary, un-dramatic fact of human death.
Bryant avoids religious rhetoric, instead using broadly spiritual language. In this way, he can address feelings shared by almost all human beings, rather than just those with particular beliefs.