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in that Adrian's 'deal with the devil' admission is an attempt at meaning, and to share responsibility as an agent, to describe horrors of the world. As he descends into madness from the syphilis, and loses control on his bearings from dementia, he holds onto some semblance of control by admitting a role in the chaos of his life that he cannot explain. Or, if there was a deal with the devil, it was partly as a way to relinquish the responsibility of agency, while taking full control of one's destiny with that crutch. Adrian yells to the crowd at the end that he was destined to turn to the devil from birth, another way to diffuse responsibility while simultaneously taking on all the shame, a double-edged sword. Celeste does something similar - whether she imagined it, or actually did it - the idea of making a deal with the devil only serves as a crutch. It's a support for if life doesn't work out well it's a psychological safeguard to share the burden and not internalize it alone. In the absence of God, or hope, one will seek it where they can, and after that traumatic event it seems sensible to turn to the tangible that is sin to find solace. Adrian's advisement to the crowd to live life sober and admitting to being inebriated through his own, also discounts that initial declaration that he was destined for this fate from birth, but hits on the idea that he (and Celeste, and all of us to some degree) chose to spend his life out of the sobering awareness of the world's disorder and uncontrollable cosmic forces. It's a lot easier to give that advice when you're at the end of your rope than when you're young and scared and need to turn to something tangible to alleviate that unbearable dysphoria!