Why is there so much good in a world of sinners? Why do many sinners act more honorably than Christian believers? How can wicked people write and perform works of beauty? How much can believers benefit from the talents and knowledge of unbelievers? Can believers cooperate with unbelievers? These perplexing questions are addressed by the doctrine of common grace. This brief primer introduces the reader to the doctrine with definition, historical development, exposition, and application.