Machen was not one to pussyfoot about theological differences. But he also recognized the chasm that lay between Catholoicism and Protestant liberalism ( Christianity and Liberalism ):
“Far more serious still is the division between the Church of Rome and evangelical Protestantism in all its forms. Yet how great is the common heritage which unites the Roman Catholic Church, with its maintenance of the authority of Holy Scripture and with its acceptance of the great early creeds, to devout Protestants today!
“We would not indeed obscure the difference which divides us from Rome. The gulf is indeed profound. But profound as it is, it seems almost trifling compared to the abyss which stands between us and many ministers of our own Church. The Church of Rome may represent a perversion of the Christian religion; but naturalistic liberalism is not Christianity at all.”