[...] when life starts to feel insubstantial, you may be tempted to abuse substances. Wallace hints at this connection between feeling insubstantial and the abuse of substances by consistently writing "Substance abuse" with a capital "S". He does so because part of what's at stake in substance abuse is a hunger for some uppercase Substance that could, for once, satisfy desire and appease the head's hunger for transcendence.
But this hunger for some final Substance is a dead end. You can't get rid of it. [...]
though Miller doesn't mention it in this chapter, this relates to SFT's desire to get all the pampering out of one's system, etc