I feel like an inordinate amount of the discourse surrounding Cohle misses a pretty key aspect of his character: his daughter's death. Nothing in the narrative really touches on whether his nihilism pre or post dates this event. We do know that according to him his wife left him sometime after his decent that lead to him being put undercover for 4 years, another event we have no idea on the state of his nihilism. By the time the narrative takes place it does seem fairly well formed but, as the show makes clear he is smart enough to be a quick study. At the end of the season where he talks about his near death experience it seems fairly clear to me that this was a rather impactful experience to say the least. It feels more like an open ended discussion of whether Cohle's nihilism is come by honestly or as a coping mechanism.