It’s widely known and accepted that the Buddha and his teachings didn’t emerge out of a vacuum. I think everyone accepts that the Buddha was one of many samanas, and we know he studied with other samanas before finding his own path. So it shouldn’t be a surprise that Buddhism shares many ideas with other Indian religions. So what is uniquely Buddhist? Has anyone ever researched this and complied a table, for example, of things that Buddhism shares with other Indian religions? I read a book that attempted to do this with meditation (this book), but I don’t think I’ve seen a comprehensive list of everything (kamma, rebirth, devas, a layered model of heavenly realms, etc.). Based on my limited knowledge, it seems that there’s very little that’s uniquely Buddhist. Recently I read that the Ficus Religiosa (the kind of tree the the Bodhi tree is) was considered sacred before Buddhism. So it’s no accident that the Buddha is represented as attaining enlightenment under that kind of tree. I guess to limit the scope of this question, I’ll add that I’m only talking about early Buddhism.
To be clear, I’m not talking about arguments like the one that goes “The Buddha only taught rebirth because that idea was prevalent at the time.” I’m also not implying that just because Buddhism shares something with the Upanishads or the Jains it’s automatically wrong. I’m just curious.