The novel speaks to a condition in which human beings are shown to struggle within both dualities of being in the world.  Dr. Jekyll understands this aspect of his own being in the world:  "With every day, and for both sides of my intelligence, the moral and the intellectual, I thus drew steadily nearer to that truth, by whose partial discovery I have been doomed ... that man is not truly one, but truly two ... I hazard the guess that man will be ultimately known for a mere polity of multifarious, incongruous and independent denizens."  For Jekyll, consciousness is understanding that there is an intrinsic division within the consciousness of man.  The elements of construction collides with that of destruction.  

The novel's statement about the duality of man exists in this point.  Consciousness exists in understanding that there is not one singular construction of humanity.  Rather, there are different aspects to the personality of the individual that has to be understood.  The duality of man is one that plagues individuals because social construction tells a different narrative.  Jekyll's desire to understand this aspect of his own being embodies the struggle that the modern individual undertakes.  The understanding of self is one in which multiple visions of the self have to be embraced and fully grasped.  It is in this where complexity exists in the modern predicament for the duality of man creates human beings as complex creatures.