Morals and Natural Law

It does not take religion to see that morals do not change over time. In other words, what might have been bad to do years ago, is still bad to do today. Natural Law helps us realize this. Take, for example the eye. We know that the nature and purpose of the eye is to help the person see. Suppose an object gets lodged into the eye. This would hinder the eye from fulfilling it's purpose. When this happens, it would be considered an evil. But suppose that one goes to the eye doctor and helps that person see again. That would be considered a good. What helps a thing come to fulfillment is good and what hinders a thing from its fulfillment is bad. So when it comes to ethics, what determines good from evil would be weather or not that action helps that person and society obtain its purpose. Does it go against its nature or not.
Without religion, we can see we are made for community. In order for society to build, reproduction needs to happen. Darwin understood that. This requires a male and female, a community of two persons. Moreover; a child cannot feed itself. The mother needs to look after the child. So the mother and father needs to look after the common good of that societal unit. Sociologists should understand that. So we need community and to do the common good for the community of humanity. Murder is bad for society, just like a thing lodged in the eye is bad for the eye. Their purpose is defeated. That is why contraception, abortion, homosexuality, pre-marital sex, fraud, dishonesty, jealousy and anything else that hinders the building up of humanity is bad. It wounds society.
That is where God comes in and offers us healing. Note: This was just pure reasoning. Pagans believed this. There is more reasoning which comes from God. God's reasoning is not natural like the reasoning above. It is rather supernatural. So from the religious point of view, it still comes up short, but it is not wrong.