Last Sunday in Episode 5, entitled The Secret Fate of All Life, Rust Cohle (played by Matthew McConaughey) introduced True Detective's audience to the concept of Eternal Return, a hypothesis close to my heart, particularly as it is one I thought up for myself after nearly a decade of rumination, only to learn later (with the advent of Wikipedia) that the concept had already been around for a long, long time.
Eternal Return is a hypothesis that, in various forms, has been speculated upon since ancient times, although it fell largely into obscurity with the rise of Christianity. Rust Cohle's take on it is akin to that of Nietzsche in his philosophical novel Also sprach Zarathustra - we not only return after death to the very same lives we lived before but also repeat every single choice and action we made the last time around. This could be described as a pessimistic take on Eternal Return, and Cohle describes himself as a pessimist (in the philosophical sense) in Episode 1.
An optimistic take - such as the one I discussed last year in my post Why Time Travellers Never Turn Up To Dinner - would argue that there are enough variables and random occurrences to ensure a variety of outcomes - ie the alternative or parallel universes or timelines associated with the multiverse hypothesis. But of course, with the infamous Yellow King of Carcosa lurking in the show's background, the optimist's take on Eternal Return would seem out of place.