Essayist Terrence Heath is troubled by a story in which a church-going person commits a nasty deed. That prompted him to extensively quote the WikiHow page on How to Determine Moral Principles Without Religion. This is to counter the claim that all morals come from God and if you aren't a believer you are without morals. That is contradicted first by the supposed believer who committed the nasty deed.
The second contradiction is from noting that nobody insists that every last Biblical law must be followed. We actually find many of those "laws" repugnant. Therefore there is some method outside of (or in addition to) divine revelation to determine what is moral.
Other thoughts from the WikiHow article.
* Morals should be based on improving this life, not in getting into the next.
* Consider what moral principles you never violate. One example for most people is aggressive violence.
* Make your moral code consistent by examining principles that you sometimes violate. Will you lie when your partner asks, "Does this make me look fat?"
* Do your principles promote happiness and lessen suffering?
* Developing a personal moral code does not lead to moral relativism, in which all moral codes are equal. There are objective criteria to allow ranking one set of principles as better or worse than another.
My own moral principles are based on two questions. Does an action harm or improve mental health in myself or another? Does an action build or tear down community?