good vs evil

i do not believe in absolute good or evil. to say that these constructs are absolute and concrete is to say that they are an inherent part of nature, which seems to me a bit silly. good and evil are probably just human abstractions, and most likely not at all absolute across the universe. their definitions aren't even the same throughout human history or across cultures on earth or even with other animals. (i say probably because there is no way to prove such a thing one way or the other.) take cultures who practice human sacrifice as an example. to everyone who doesn't do this, it seems not good. but to those cultures, it is not evil, only their way of life. torture was very prevalent in the middle ages and it didn't seem a big deal to them. but now torture is some terrible, evil thing. and humans don't apply morality to animals. it is so wrong for a person to kill another, but if a shark or tiger does it, it isn't evil, just nature. humans are still a part of nature now matter how hard they try to distance themselves from it. and nature is indifferent.