“Without an understanding of common grace, Christians will believe they can live self-sufficiently within their own cultural enclave. Some might feel that we should go only to Christian doctors, work only with Christian lawyers, listen only to Christian counselors, or enjoy only Christian artists. Of course, all non-believers have seriously impaired spiritual vision. Yet so many of the gifts God has put in the world are given to nonbelievers. Mozart was a gift to us–whether he was a believer or not. So Christians are free to study the world of human culture in order to know more of God; for as creatures made in His image we can appreciate truth and wisdom wherever we find it.
Without an understanding of common grace, Christians will have trouble understanding why non-Christians so often exceed Christians morally and in wisdom. Properly understood, the doctrine of sin means that believers are never as good as our true worldview should make us. Similarly the doctrine of grace means that unbelievers are never as messed up as their false worldview should make them. For in the Christian story, the antagonist is not non-Christians but the reality of sin, which (as the gospel tells us) lies within us as well as within them.
And so we are likely to be on firm footing if we make common ground with non-Christians to do work that serves the world. Christians’ work with others should be marked by both humble cooperation and respectful provocation. An understanding of common grace, as well as an experience of God’s pardoning grace in Christ, should lead us to freely and humbly work with others who may not share our faith but can be used greatly by God to accomplish enormous good.”
-Timothy Keller, in Every Good Endeavor: Connecting Your Work to God’s Work