In an essay on the importance of Christian scholarship, Machen demonstrated a strong view of the antithesis between believers and unbelievers (so much so that one might be tempted to think he was Dutch).
One thing needs always to be remembered in the Christian Church—true Christianity, now as always, is radically contrary to the natural man, and it cannot possibly be maintained without a constant struggle. A chip that floats downwards with the current is always at peace; but around every rock the waters foam and rage. Show me a professing Christian of whom all men speak well, and I will show you a man who is probably unfaithful to His Lord. (J. Gresham Machen, “The Importance of Christian Scholarship” in Education, Christianity, and the State: Essays by J. Gresham Machen, p. 23.)
Such a view should have significant implications regarding how Christians should live in this world, education being just one prime example.