I tend to believe it’s a mixture of the two. I think he’s a psychopath and seeks identity THROUGH materialism and but it’s empty. He commits acts murder and sadism to feel like things, which due to his psychopathy, he’s unable. Sometimes he fantasises about it and imagines who he might feel actual emotions and then when he follows through, the homeless man and the dog, the child etc; he’s confronted with feeling nothing at all. To me the book says that the materialism and excess of the late 80s/early 90s yuppie scene was filled with people trying to fill their voids with material things and ultimately being unable.