"Everything is Dual; everything has poles; everything has its pair of  opposites; like and unlike are the same; opposites are identical in  nature, but different in degree; extremes meet; all truths are but  half-truths; all paradoxes may be reconciled."--The Kybalion.
This Principle embodies the truth that “everything is dual”;  “everything has two poles”; “everything has its pair of opposites,” all  of which were old Hermetic axioms. It explains the old paradoxes, that  have perplexed so many, which have been stated as follows: “Thesis and  antithesis are identical in nature, but different in degree”; “opposites  are the same, differing only in degree”;  “the pairs of opposites may  be reconciled”; “extremes meet”;”everything is and isn’t, at the same  time”; “all truths are but half truths”;”every truth is half-false”;  “there are two sides to everything,” etc., etc.,etc. It explains that in  everything there are two poles, or opposite aspects,and that  “opposites” are really only the two extremes of the same thing,with many  varying degrees between them. To illustrate: Heat and Cold,  although”opposites,” are really the same thing, the differences  consisting merely of degrees of the same thing. Look at your thermometer  and see if you can discover where “heat” terminates and “cold” begins.  There is no such thing as “absolute heat” or “absolute cold”–the two  terms “heat” and “cold” simply indicate varying degrees of the same  thing, and that ‘same thing” which manifests as “heat’ and ‘cold” is  merely a form, variety, and rate of Vibration. So”heat” and “cold” are  simply the “two poles’ of that which we call “Heat”–and the phenomena  attendant there upon are manifestations of the Principle of Polarity.
The same Principle manifests in the case of “Light and  Darkness,”which are the same thing, the difference consisting of varying  degrees between the two poles of the phenomena. Where does “darkness”  leave off, and “light”begin? What is the difference between “Large and  Small”? Between “Hard and Soft”? Between “Black and White”? Between  “Sharp and Dull”? Between “Noise and Quiet”? Between “High and Low”?  Between “Positive and Negative”? The Principle of Polarity explains  these paradoxes, and no other Principle can supersede it. The same  Principle operates on the Mental Plane. Let us take a radical and  extreme example-that of “Love and Hate,” two mental states apparently  totally different. And yet there are degrees of Hate and degrees of  Love, and a middle point in which we use the terms “Like or  Dislike,”which shade into each other so gradually that sometimes we are  at a loss to know whether we “like” or “dislike” or “neither.” And all  are simply degrees of the same thing, as you will see if you will but  think a moment. And, more than this (and considered of more importance  by the Hermetists), it is possible to change the vibrations of Hate to  the vibrations of Love, in one’s own mind, and in the minds of others.  Many of you, who read these lines, have had personal experiences of the  involuntary rapid transition from Love to Hate, and the reverse, in your  own case and that of others. And you will therefore realize the  possibility of this being accomplished by the use of the Will, by means  of the Hermetic formulas. “Good and Evil” are but the poles of the same  thing, and the Hermetist understands the art of transmuting Evil into  Good, by means of an application of the Principle of Polarity. In short,  the “Art of Polarization becomes a phase of “Mental Alchemy” known and  practiced by the ancient and modern Hermetic Masters. An understanding  of the Principle will enable one to change his own Polarity, as well as  that of others, if he will devote the time and study necessary to master  the art.