What Is Faith?

J. Gresham Machen wrote this defense of Christian faith in 1925, during the height of the fundamentalist-modernist controversy that was splitting American Protestant denominations. As a professor at Princeton Theological Seminary and later founder of Westminster Theological Seminary, Machen faced liberal theologians who redefined faith as mere religious feeling or ethical commitment while abandoning supernatural beliefs. The book emerged from his conviction that modernist redefinitions of faith had emptied Christianity of its essential content.

Machen argues that genuine Christian faith has three inseparable elements: knowledge of the facts of the gospel, intellectual assent to those facts as true, and personal trust in Christ based on that knowledge. He systematically dismantles the liberal notion that faith can exist independently of doctrine or historical facts, insisting instead that faith must have cognitive content to be meaningful. Faith is not a leap in the dark or a feeling of dependence, but a response to revealed truth about God's saving work in Christ. Machen demonstrates that this understanding aligns with both New Testament teaching and the historic Christian tradition, while showing how modern attempts to separate faith from facts ultimately destroy both.

The work remains influential in Reformed and evangelical circles for its precise theological reasoning and its model of how to defend orthodox Christianity against reductionist alternatives. Machen's arguments anticipated many later debates about the relationship between faith and reason, and his insistence on faith's cognitive dimension continues to shape conservative Protestant apologetics. Who should read this: Students of theology and church history seeking to understand early twentieth-century theological debates, pastors and teachers defending traditional Christian beliefs, and anyone interested in Reformed perspectives on the nature of faith. Those looking for devotional material or practical spiritual guidance should look elsewhere.