That question is ubiquitous among the believers quiver. You can't help them until they are ready.

My reply...

If you need a book to tell you your morals: you are just a naturally immoral person. If you are choosing a book for morals, try one which says rape is wrong, slavery is wrong, and killing people for mild infractions is wrong.

nobody knows I am agnostic.......so nope......

This I think is one of the best retorts to that question.
I don't know who coined it though.

If you can't tell the difference between right and wrong, you don't lack religion, you lack empathy.

not a religious friend. religious antagonists yes. my friends don't ask obnoxious questions like that. they know i am an ethical person. ask your friend why she thinks people can't be good unless they have a promise of heaven or the threat of hell, and whether it isn't more ethical or moral to be good because that's the kind of person you are!

g

My sense of morality stems from having a healthy respect for all life and a desire to live in harmony with my fellow creatures on this planet

I believe you and your religious friend share the source of your morality.

It begins when we are and selfish and our parents teach us the difference between right and wrong. Then, as we grow, siblings, teachers, friends, etc. continue to impress moral lessons on us in a variety of ways because the morality we learn improves how well the social structure works for everyone. Finally, when we are mature enough to think it through, we realize that everyone feels the same pain and sorrow that we feel in response to the behavior of others. Our response to that knowledge is to refrain from such behaviors. For most, the circle of influence extends from family to friends, and then to larger groups in which we find interest. Finally, the edges of that circle of influence begin to fray and we find it more and more difficult to sympathize with 'faraway unknown others.' When we give, we give only leftovers. Really, how many of us are willing to give--to our own detriment--to benefit the lives of others (unlike what we are willing to give to our family and friends), whom we have never met and never will?

The initial helping of selfishness and survival instinct, with which we are all born, remains and continues into adulthood to a greater or lesser degree for all--religious and nonreligious alike. Thus, the authors of the Bible received their moral education in the same multitudinous ways that you and your friend received yours. The only difference is that some attribute moral knowledge to a supreme being instead of to the evolution of empathy in their own lives.