Almost everything that matters in life is a matter of perspective. Think about health and wealth. A poor person in the U.S. would be considered rich in some countries. Likewise, a healthy person may actually be sick depending on different criteria used to determine fitness. Or take "brilliance." A genius of 4,000 years ago probably didn't know things that a middle school student does today, and our best current knowledge might appear simple and naive to observers 4,000 years from now. The same goes for good and evil. Everyone measures these by their own conceptions of happiness, pleasure, virtue, etc. To be objective doesn't mean that everyone must be in full agreement about the particulars of each case, it just means that given a standard of well-being that everyone naturally cares for, as rational, sentient beings, there is a spectrum of various physical and mental states that can be weighed against it.
He who loves God cannot endeavour that God should love him in return - Baruch Spinoza
