I could fight the devil; I could overcome every sin that ever tempted me, if it were not that I had an enemy within. Those Diabolians within do more service to Satan than all the Diabolians without. As Bunyan says in his Holy War, the enemy tried to get some of his friends within the City of Mansoul, and he found his darlings inside the walls did him far more good than all those without. Ah! Christians, thou couldst laugh at thine enemy, if thou hadst not thine evil heart within; but remember, thine heart keeps the keys, because out of it are the issues of life. And sin is there. The worst thing thou has to fear is the treachery of thine own heart.