"Everything is dual, everything has polarity, everything has its opposite. All things are paired by an opposite, the similar and opposite are the same, as opposites are united in nature, differing only in degree. The ends meet, all half-truths are united in completion and the paradox is reconciled."
THE KYBALION

The Forth Great Hermetic Principle - the Principle of Polarity - encompasses the truism that all things that are manifest have two sides, two aspects, two poles; a duality with opposite polarities at each end. Those old paradoxes that have always confounded the minds of men are reconciled when one understands this principle. Men have always recognized something of the nature of this principle and tried to express it in various statements, maxims or aphorisms like these: "At the same time, everything both is and is not." "All truths are no more than half-truths"; "All truth is half false"; "Everything has two sides"; "There is an obverse for every reverse", and so on.

The hermetic teachings say of the diametric difference that exists between seemingly opposite things is only a question of degree. And they affirm that every pair of opposites can be reconciled, the thesis and the antithesis are identical in nature and differ only in degree. The universal reconciliation of opposites is recognized in this Principle of Polarity. Examples of this principle are everywhere, when the real nature of things is examined. Spirit and matter are no other than poles of the same thing, being merely planes seemingly separated by degrees of vibration. The ALL and the many are the same, their only enduring difference being in the degree they manifest to the mind. In like manner, the LAW and the many laws are separate poles of the same, and a single, thing. It is the same with the PRINCIPLE and principles, with the infinite MIND and the finite mind.

On the physical plane we find that hot and cold are identical in nature, their only difference being a simple question of degrees. The thermometer indicates degrees of temperature, being the lower pole being called "cold" and the higher one called "heat". Between these two there are many degrees of hot and cold and whichever name we may give them is correct. Of any two degrees, the higher one is always hot in comparison with the lower one, which is therefore colder. There is not any one place on the thermometer at which heat absolutely ceases and cold begins. Everything can be broken down into measurements of higher or lower vibrations. The same words: "higher" and "lower", that we are compelled to use are nothing more than the two poles of the same thing; the terms are relative. It is the same with "East" and "West". If we travel around the world in an Eastern direction we will end up in a place to the "West" of the place from which we start. If we go sufficiently far to the North we will be traveling South, and just the opposite.
Light and darkness are also opposite poles of the same thing, with many degrees of variation between the two poles. The musical scale is the same. Leaving one note we arrive at another and so on, the differences being again a question of degree. In spectrum of color another variation occurs, the vibratory intensity being the only difference between red at one end and violet at the other. Things that are and small are relative as are noise and quiet, hard and soft, sharp and blunt. Positive and negative are two polarities of the same thing, between one pole and the other are countless different graduations.
Good and bad are not absolute; rather we call one end of a scale good and the other bad but mean that they are good or bad relative to each other and depending on the value we have given them. One thing may be less good than another that is higher on the scale of good, yet that which is higher might in turn be lower than something else depending on the range of the scale by which we measure them.

A similar scale occurs on the mental plane. Love and hate are considered diametrically opposed, in total opposition and irreconcilable. However by applying the Principle of Polarity we find that absolute love does not exist, nor does absolute hate; they are relative one to the other. Both are no more than terms applied to two poles of the same thing. Beginning at any point on the scale and you can find "more love" or "less hate" by ascending, or "less love" by descending. This is a certainty that is true regardless of where we start on the scale. Many degrees of both love and hate exist on the spectrum and it could even be said that there is a half way point where pleasure and aversion are so intermingled that one cannot distinguish them. Valor and fear are also governed by this same rule. Pairs in opposition exist everywhere. Wherever we find one thing, we will find its opposite also: the two polarities.
This fact is what allows for the hermetic mental transmutation from one mental state to another by shifting the polarity. Different types of things cannot be transmuted into something else, but a thing can be refined without becoming something else. Therefore love cannot be transformed into east or west, red or violet, but can change to hate and equally hate can change to love, by changing polarity. Bravery can be transformed into fear and vice versa. Things that are hard can become soft, hot changed to cold, and so on but always it is things changing by degrees within the range of their own kind. In this way a cowardly man, if his mental vibrations rise on the scale between fear and bravery, may become filled with courage and scorn danger. Likewise, someone who is lazy can become active and energetic by polarizing toward the desired quality.

Disciples familiar with the procedures used to bring about mental changes in their pupils may not be familiar with the scientific principles that bring about those changes. Nonetheless, once you understand the principal of polarity it immediately becomes apparent that movement on the scale of polarity causes those mental changes. Such changes are not in the nature of changing something into something totally different but rather they are the result of a change in the degree of polarity, it is the degree of difference that matters. To take and example from the physical world, it is impossible to change heat to make it sharper or more flexible, heavier or taller, but it can easily be transmuted toward cold just by slowing the vibration. In the same way love and hate are reciprocal and can be transmuted from one to the other, as can fear and bravery. Fear cannot become love, or change into hate. All mental states belong to various classes, each with their opposing poles, and it is their nature that can be transmuted.
It is easy to understand that, just as phenomena on the physical plane, the dual poles of mental states are often classified respectively as positive and negative. Therefore we say that love is positive compared to hate, bravery more positive in energy than fear, activity compared to inactivity etc. And it is noticeable, even disregarding the principle of vibrations, that the positive seems to be elevated compared to the negative polarity. Nature tends to flow toward the positive polarity.

Besides changing the polarity of our own mental states by applying the art of polarization, the same demonstrative phenomenon that affects our mental states can be demonstrated to influence others also. A good deal has been written about this in recent years. Once someone understands that mental transmission of this type is possible, that thoughts can be transmitted from one person to another, then we can understand how it is possible to effect someone else with certain levels of vibrations, resulting in a change of their polarization. Most results obtained by these "mental treatments" are accomplished according to this principle of polarities. As an example consider a person who is sad, melancholic and fearful. Someone who understands this mental science elevates his own mental state to the desired degree by skillful exercise of his will in order to obtain the polarization required in his own mental state. Then by induction he can produce a similar mental state in the other person because the intensified vibrations polarize the mind of the patient toward the positive polarity on the scale rather than moving toward the negative. Hence their sorrow, melancholy and fear are transformed into bravery, contentment and similar inner states. Meditation on the matter will reveal that mental changes are almost always made along the lines of polarity. That is, they are a change of degree rather than of kind.
Understanding this great hermetic principle allows a better understanding or our mental states, and those of others also. Further, it becomes apparent that those mental states differ only by degrees, and by understanding this fact we are able to elevate inner vibrations through will, changing their polarity. In this we become the owner of our thoughts, instead of being enslaved and made servant to them. This knowledge will also allow you to offer assistance to others by using these methods appropriately to change their polarity. It is desirable to become familiar with this principle because understanding it well will provide greater light when dealing with dark and difficult problems.