One system that really excels at exploring philosophical themes is Numenera. Its setting encourages players to confront ideas about the nature of existence and what it means to be human after the fall of civilization. The focus on discovery and the myriad of choices players can make often leads to discussions about morality and free will.
Another great option is Blades in the Dark, especially when you're dealing with concepts like loyalty, betrayal, and the consequences of one's actions in a gritty, morally gray world. Plus, the mechanics around characters' vices and traumas can really spark deep conversations about personal morality.
I'd love to hear what specific themes you're interested in. Are you leaning more towards a gritty, dark narrative or something more whimsical yet thought-provoking?
