Thoughts from Hatsumi

“In the world of combat survival, the superior fighter makes use of all advantages at hand, including the influences of the mind. As a means of increasing the difficulty for an enemy, ninja of old developed the strategy of kyojitsu tenkan ho, or the interchange of the concepts of falsehood and actuality.
A strategy for winning that relies on the presentation of truth and falsehood in ways that permit the antagonist to be deceived, kyojitsu tenkan forms the basic approach for all ninjutsu activities and thinking. Because the ninja is dealing freely with the concepts of truth and falsehood, fluidly bending one into the other, he must be well grounded in his own concept of reality. To prevent becoming lost, misguided, or swallowed up by his own deception or awareness altering, the ninja must maintain seishin, or purity of heart. In this sense, the word pure means “complete” or ” total.” The ninja carries the truth in his heart,
though he may appear in many psychological guises to others. His intentions remain resolute, though others may have no idea what those commitments entail. Because he is totally honest with himself at all levels of introspection, he can venture into the realm of falsehood and untruth without defiling himself or his spirit. He can willingly plunge into the cold darkness, knowing full well that he has the power to create his own light from the brightness he carries in his heart.”