Is there such a thing as an entirely objective code of ethics? What really tells you that theft (or murder or copyright infringement) is a Bad Thing to do?
Religious people can usually point to some text or writing and say, “I believe that X is wrong, because my religion says so.” There’s also usually some penalty for Bad behavior, whether that be bad karma, or eternal hellfire, or reincarnation into the body of a cockroach. However it works, most religions provide guidelines to help their adherents live “virtuously” (whatever that is defined to mean).
But if you’re not religious, or if you just disagree with the “Ethics” chapter in your holy book, how do you know what’s Good and what’s Bad? What is it that tells you that, for instance, it would be wrong to kill someone for his money, but killing in self-defense might sometimes be justified?
(Simply saying, “My conscience tells me,” is not really any answer. Your conscience is part of your mind, so if it tells you not to do X, you must have (consciously or unconsciously) decided that X is a Bad Thing in this situation.)