oyyoyyoy,
is it better to not do something cause your a good prson, or cause hashem said so. killing for example
What defines a good person is societally and culturally dependent, as oomis eloquently described. What one society considers morally repugnant behavior another might see as great virtue.
Some behaviors, such as killing and stealing, seem to carry a greater universal morality than others, such as dietary laws. I believe this sense of heightened morality comes from the fact that societies cannot be built or maintained unless these behaviors are curtailed. Therefore, there are some basic moral concepts that all humans, who are social creatures, instinctively adopt. Also, we are wired to feel empathy, so most humans can develop a sense of, “what is hateful to me, do not do to others.”
Torah changes the entire ball game. Instead of morality from within, which can be influenced by environment, culture, and society, Torah gives us morality from Heaven. Some of that morality will line up with our instincts, but some will not. Building a society around this heavenly moral code is what the Jewish people are all about.