"I shall not attempt to teach a tiger the virtues of vegetarianism; but I shall as hopefully attempt that task as I would try to convince an unregenerate man of the truths revealed by God concerning sin, and righteousness, and judgment to come. These spiritual truths are repugnant to carnal men, and the carnal mind cannot receive the things of God. Gospel truth is diametrically opposed to fallen nature; and if I have not a power much stronger than that which lies in moral suasion, or in my own explanations and arguments, I have undertaken a task in which I am sure of defeat. . . Except the Lord endow us with power from on high, our labor must be in vain, and our hopes must end in disappointment."
--Charles Spurgeon, An All-Round Ministry: Addresses to Ministers and Students