In this article, Ed Welch addresses the question of how the church can be in the world but not of it. He argues that the church always moves between two extremes in its relationship to the world: either tempted to withdraw into a “gated community” to protect purity, or tempted to blend in with the world’s cultural forms in order to gain relevance. Welch maintains that Ephesians 5:3-20 teaches how to be in the world but not of it. First, don’t partner with the world, but keep yourself pure (5:3-7). Second, get involved with a purpose, invading the world with light (5:8-14). Third, be very careful and very thankful in how you live (5:15-20). Welch concludes we have the difficult, twofold task of guarding our hearts from the influence of the world while yet shining as light into the world.