American Presbyterian theologian (1881-1937), New Testament scholar at Princeton Theological Seminary from 1906 to 1929, and founder of Westminster Theological Seminary (1929) after Princeton's reorganization under modernist influences. Machen's most influential book, Christianity and Liberalism (1923), remains one of the sharpest Protestant polemics ever written — arguing that theological liberalism is not a kind of Christianity at all but a different religion using Christian vocabulary.
Machen was the 20th century's most effective defender of historic Protestant orthodoxy against liberal drift. Four points. (1) Christianity and Liberalism. His thesis: liberalism rejects the supernatural core of Christianity (inspiration, deity of Christ, virgin birth, substitutionary atonement, bodily resurrection, second coming) while retaining the vocabulary — essentially a different religion in Christian clothing. The book is short, sharp, and still definitive. Every generation's version of "progressive Christianity" is a rebranded iteration of Machen's target. (2) Princeton's reorganization. When Princeton Seminary was restructured in 1929 to accommodate theological pluralism, Machen led the exodus that founded Westminster Theological Seminary in Philadelphia. Westminster remains a confessional Reformed institution. (3) Founding of the OPC. When the PCUSA's denominational Board of Foreign Missions proved modernist, Machen led the founding of the Independent Board of Presbyterian Foreign Missions (1933) and, after being deposed by the PCUSA, the Presbyterian Church of America in 1936 — later renamed the Orthodox Presbyterian Church. (4) The Virgin Birth of Christ (1930) and The Origin of Paul's Religion (1921) — technical NT scholarship defending supernatural Christianity against Liberal and History-of-Religions critiques. Machen died age 55 of pneumonia contracted while traveling to preach in North Dakota. His last telegram to fellow Reformed pastor John Murray: "I'm so thankful for the active obedience of Christ. No hope without it." A theologian's deathbed.