One of my favorite Tim Keller sermons is one on Romans 7 entitled Splitness where he makes extensive use of Robert Louis Stevenson’s classic The Strange Case of Dr. Jekyll and Mr. Hyde. Here is the part of the book he quotes from for the meat of his argument. I used it for a sermon on Jesus’ parable of the Pharisee and the Tax Collector in Luke 18.

I resolved in my future conduct to redeem the past; and I can say with honesty that my resolve was fruitful of some good. You know yourself how earnestly in the last months of last year, I laboured to relieve suffering; you know that much was done for others, and that the days passed quietly, almost happily for myself. Nor can I truly say that I wearied of this beneficent and innocent life; I think instead that I daily enjoyed it more completely; but I was still cursed with my duality of purpose; and as the first edge of my penitence wore off, the lower side of me, so long indulged, so recently chained down, began to growl
for licence.

It was a fine, clear, January day, wet under foot
where the frost had melted, but cloudless overhead; and the Regent’s Park was full of winter chirrupings and sweet with spring odours. I sat in the sun on a bench; the animal within me licking the chops of memory; the spiritual side a little drowsed, promising subsequent penitence, but not yet moved to begin.

After all, I reflected, I was like my neighbours; and then I smiled, comparing myself with other men, comparing my active goodwill with the lazy cruelty of their neglect. And at the very moment of that vain-glorious thought, a qualm came over me, a horrid nausea and the most deadly shuddering. These passed away, and left me faint;
and then as in its turn the faintness subsided, I began to be aware of a change in the temper of my thoughts, a greater boldness, a contempt of danger, a solution of the bonds of obligation. I looked down; my clothes hung formlessly on my shrunken limbs; the hand that lay on my knee was corded and hairy. I was once more Edward Hyde.