No one ever fights earnestly against the world, the flesh, and the devil unless he has engraved on his heart certain main principles that he believes. He might hardly know what they are, and may certainly not be able to define or write them down, but they are there, and consciously or unconsciously, they form the roots of his Christianity. Wherever you see someone, whether rich or poor, learned or unlearned, wrestling bravely with sin and trying to overcome it, you can be sure there are certain great principles that person believes.