A Letter to Rome examines Charles Hodge’s 1869 response to Pope Pius IX and the First Vatican Council, a rare moment when American Presbyterianism spoke directly to Rome. With clarity and charity, Hodge explains why the core issues of the Reformation—Scripture alone, the sufficiency of Christ, and the nature of church authority—made unity impossible. This episode revisits that letter and asks what modern Protestants can learn from Hodge’s firm convictions and pastoral tone in an age of renewed ecumenical pressure.