Without Nature or Plato or Aristotle or God to hand us our ideals, how do we know how to view good and evil? We must do what every thinking human being has done both before and after the rise of philosophy. You do not just accept whatever most people in your culture happen to believe. When I recommend Jefferson's ideals, they should carry no weight at all simply because you are an American and they were formulated by a revered American. Unless you find that they resonate with you, you have no good reason to adopt them or take pride in your nation's moral heritage. You should read widely, survey the diversity of ideals that human kind has developed, try to put yourself in their shoes, and reflect. Then you look within and ask certain questions.