It is perhaps a strange story, but it does present the author's view on human nature. But, sadly, his view is wrong as it contradicts the view of man's nature found in God's word. Humans have only one nature and it is corrupted by sin. "None is righteous, no, not one; no one understands; no one seeks for God. All have turned aside; together they have become worthless; no one does good, not even one." Romans 3:10-12 From birth we are children of wrath, dead in our sins. We can by nature do nothing that pleases God or could contribute to our salvation. In our heart, there is the potential for us to be able to do every kind of evil deed. Given the right time and circumstances, we could do every evil deed that has ever been done. But for the grace of God, we are not all as degraded as we could be.
God restrains evil in this world by a number of ways. He uses the government to restrain evil by making and upholding laws, even by punishing lawbreakers by death. God has given us consciences which restrain people from doing evil. People often want to feel good about themselves so they give themselves to good deeds. Or they are afraid of the thoughts and opinions of others. Some, desiring to obtain salvation, work hard to show kindness and charity to others. Also believers are God's salt and light in this world. By proclaiming the truth and walking in godliness, we have a positive influence in this world, as it reminds others of good and evil. These are all ways in which people are prevented from being as bad as they could be.
People are born liking sin. We enjoy it, even if the consequences are bad. And as we indulge and feed our desire for sin, we become more and more corrupt. And, as in the case of Dr. Jekyll, in the end, we look more like Mr. Hyde than we could ever imagine. We become monsters of sin. Even our facial features will reflect our evil nature. Let your lusts gallop away unrestrained, and they will drag you into filth and mud you never dreamed possible. Mr. Stevenson was right in a way about this aspect of human nature. If we continue to practice sin, it will corrupt us and turn us into horrible ogres.
Thankfully, in Jesus Christ there is hope. For God doesn't just forgives us, He changes us. He takes our old evil hearts out and puts in a new heart. God changes us from Mr. Hyde to Dr. Jekyll, yes even more than that for He give us new life in Christ so we begin to act more like Him. This is the great new birth.
Although we are now new creatures in Christ, yet we have remaining in us the sinful flesh. This unredeemed flesh is what makes us still sin. We are called to "put to death" our sins. (Colossians 3:5) Mr. Hyde must die. Putting sin to death is hard. It takes work, sweat, and agony. We must hunt down our sins and slay them when we find them and keep beating them down all our lives. The Christian is called to be the executioner of his own sin, even of those sins we love. This is very hard. I have found it much harder than I ever imagined. The sins are like a terrible beast that fight savagely. And even after a long battle, with many cuts and bruises, that results in victory, yet this subdued sin can rise up again if unattended and encouraged. Ah, but God has given us the power in this fight. We have the armor of God in this battle. Our sword when used right, never fails. We have God's promise that we will overcome and that we will be more than conquerors, not in our own strength but through the power of Jesus Christ. One day we will stand blameless and holy in the presence of God. Then the war with our sin will be done and we will live forever in pure joy and holiness.