Your friend saw this resource on bethinking.org and thought you should see it:
Why Be Good? - a review
What should motivate us to be good? This book examines four possible answers.
See the full resource online by visiting bethinking.org:
https://www.bethinking.org/morality/why-be-good-review
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bethinking.org is a collection of resources which aims to make sense of the big questions of life about God, Jesus and Christianity.