Convention and ethics

Mathematics is a convention, but not an arbitrary convention. You cannot make a coherent mathematics in which the Peano axioms of arithmatic do not exist, or fail to define the natural numbers, addition, subtraction , multiplication and division. Likewise, ethics is just convention, but not arbitrary convention. Specifically, you cannot have a fully rational ethic in which it is acceptable to treat people as purely means to ends, or to consider their needs and desires fundamentally less important than your own. It follows that rape is wrong in any truly rational ethical convention, as is murder, and even dishonesty. Evil is just the persistent choice of an irrational ethical convention for your personal convenience, or perhaps for that of an ideology you hold. It is like insisting that 1+1 = 0 when adding up what you owe to others, but that 1+1=3 when adding up what others owe to you.