Duality is expressed as an opposition.  In, out; yes, no; up, down; male, female;  God, Satan.  Everything available to us in this physicality, then, has been drawn out to the point of separation in order to form a contrast that provides learning.  Through duality comes the illusion of separation, for in Spirit there is only Unity, and in the study of separation we are able to learn about and realize the real oneness of all things.  

Within each of us duality is expressed and choices provided.  In fact, without the intervention of the Human Being, duality does not exist, without consciousness no separation.  Only Man is aware of separation, for only Man has choice.  For example, only Man has decided to split the atom.  Why?  It is through the study of the atom split that we may understand those principles that allow for the unity expressed by the entire atom, the relationship of one atom with another to form molecules, molecules joined with one another to bring forth life.  Again, the study of separation brings forth the reality of Unity, the interconnectedness of all things.

Most of us do not understand how separation leads to greater understanding, for we become lost within that separation, we have reached an impasse where there is no choice and no decision, we have settled into oblivion.  We sleep, for in sleep is a "peace" where we may luxuriate in the absence of decision-making.  Sleeping is only a temporary condition, for we must awake, we must take nutrition, we must continue to grow.  Resistance is only a delaying action.

Embrace the contrast in your life and with that embrace find Unity.  Only through the study of the "parts" may you realize the "whole".