This story deals with the obvious fact that we humans are split, dual. We have urges to do the 'right' thing, to be honorable and wise, but we also frequently fail to follow these better instincts and follow instead urges to do dishonorable, evil things. We seem to battle within ourselves. Are we really composed of two different personalities housed within the same brain, within the same person? Dr Jeckyll in this story is so convinced and manages by scientific means to actually split himself into his ordinary composite self, and his evil self whom he calls Mr. Hyde. The horror of this unnatural split is well documented here and shows what might happen were this possible.