In his book, Machen celebrates the modern advances in improving our physical lives that have come from scientific discoveries. The danger he sees is that these very successes have blinded many to the reality that there is more to life than physical well-being. They have focused exclusively on the material and have become materialists. The natural world that surrounds us, that can be seen and touched, is the only world. The supernatural, which is to say God’s acting beyond the natural in this world, is ruled out entirely. But Machen wisely alludes to the words of Jesus (Matt. 16:26): What will it profit a man to gain the whole world and lose his soul?

The great purpose of Machen’s book is to insist that only true Christianity can answer the challenge of materialism and to show that true Christianity is entirely different from and opposed to liberal or modernistic pseudo-Christianity. His reflections on the nature of true Christianity in each chapter show the profound and powerful importance of these truths. But before he develops this great theme, he reflects briefly on the broader issues confronting Christians in our times, particularly naturalism and materialism. “Material betterment has gone hand in hand with spiritual decline,” he writes.

As Machen sees it, “modern unbelief” has not just attacked true religion but has also undermined the higher life of individuals more generally. He sees a materialistic worldview as restricting the freedom of individuals to cultivate the great achievements of the human mind and spirit. He points to the modern arts, music, and literature as evidence of modern decline of human accomplishment.