It's no secret that in Tropic of Cancer, Henry Miller is obsessed with sex. But what about that other obsession? You know—death. He actually associates the two pretty strongly; and for good reason, given that there are so many venereal diseases floating around. On a more general note, Miller—mostly through the figure of Boris—asserts that civilization has lost its grip on the life force and has been reduced to celebrating death. Looks to us like Henry is totally on board.
Sex and death, sex and death. If you get a handle that these two things are important to Henry, you'll have it made. They both provoke equal measure of pleasure and horror for him, and they're at the center of Tropic of Cancer.
Henry believes he is witnessing the death of Western civilization. He also believes that he will live through it.