Christianity they will tell us is a life and not a doctrine. Now that seems to be a devout and pious utterance, but it is radically false all the same, and to see that it is false you do not need even to be a Christian, you need have just common sense and common honesty. For when you say that Christianity is this or that, you are making an assertion in the sphere of history. You are not saying what you think ought to be true, but what you think actually is a fact. When people say that Christianity is this or that—some have ventured the absurd assertion that Christianity is democracy —when you say Christianity is this or that, you are making an assertion in the sphere of history. It is just like saying that the Roman Empire under Nero was a free democracy. It is possible that the Roman Empire under Nero might have been a great deal better if it had been a free democracy, but the question is whether as a matter of fact it was a free democracy or not. So when you say that Christianity is a life, not a doctrine, you are making an assertion in the sphere of history, because Christianity is an historical phenomenon exactly like the Roman Empire, like the kingdom of Prussia or the United States of America.
J. Gresham Machen, “Christianity Vs. Modern Liberalism”