Every thought, emotion or mental state has its corresponding rate and mode of vibration. And by an effort of the will of the person, or of other persons, these mental states may be reproduced, just as a musical tone may be reproduced by causing an instrument to vibrate at a certain rate--just as color may be reproduced in the same may. By a knowledge of the Principle of Vibration, as applied to Mental Phenomena, one may polarize his mind at any degree he wishes, thus gaining a perfect control over his mental states, moods, etc. In the same way he may affect the minds of others, producing the desired mental states in them. In short, he may be able to produce on the Mental Plane that which science produces on the Physical Plane--namely, "Vibrations at Will." This power of course may be acquired only by the proper instruction, exercises, practice, etc., the science being that of Mental Transmutation, one of the branches of the Hermetic Art. A little reflection on what we have said will show the student that the Principle of Vibration underlies the wonderful phenomena of the power manifested by the Masters and Adepts, who are able to apparently set aside the Laws of Nature, but who, in reality, are simply using one law against another; one principle against others; and who accomplish their results by changing the vibrations of material objects, or forms of energy, and thus perform what are commonly called "miracles." As one of the old Hermetic writers has truly said: "He who understands the Principle of Vibration, has grasped the scepter of Power." CHAPTER X POLARITY "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. The great Fourth Hermetic Principle--the Principle of Polarity embodies the truth that all manifested things have "two sides"; "two aspects"; "two poles"; a "pair of opposites," with manifold degrees between the two extremes. The old paradoxes, which have ever perplexed the mind of men, are explained by an understanding of this Principle. Man has always recognized something akin to this Principle, and has endeavored to express it by such sayings, maxims and aphorisms as the following: "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"--"there is a reverse side to every shield," etc., etc.