Things Unseen is both an accessible systematic theology, and a masterclass in evangelistic apologetics. Introduced by Timothy J. Keller, Foreword by Sinclair B. Ferguson, Historical Preface by Stephen J. Nichols, Afterword by Richard B. Gaffin, Jr. On a Sunday afternoon in 1935, J. Gresham Machen stepped into a broadcast booth at WIP Radio in Philadelphia and began something no one had tried before: teaching Reformed theology over the radio. In the vein of C.S. Lewis s landmark Mere Christianity talks, Machen s addresses are a crystal-clear articulation of the basics of the Christian faith, unfolding into an exceptional and persuasive explanation of Reformed theology.