What do churches that affirm the LGBTQ lifestyle, celebrate God as mother, and host drag queen performances have in common? They are not remotely Christian. While they may identify as “liberal” or “progressive” Christians, they are so far from the core of Christianity that they are altogether a “different religion.” This conclusion is the key insight of J. Gresham Machen in Christianity and Liberalism, a book that celebrates its one hundredth anniversary this year in 2023. While the presenting issues looked different a century ago, the core was the same: Liberal Christianity proclaims a toxic view of doctrine, God, man, the Bible, Christ, Salvation, and the Church. Our Lord reminded us that “the tree is known by its fruit” (Matt. 12:33). This month, we aim to retrieve Machen’s chapter-by-chapter insights to equip a new generation of Christians to discern truth from error.