[Footnote 129: Sess. V. Decree on Original Sin.] Thus, Christianity explains the origin of this conflict in the human heart, in a manner agreeable to reason and human experience. But it does more. It reveals to us the purpose of this conflict. Why does our Lord leave us subject to this strife? The same holy Council I have quoted already, answers distinctly; this incentive to sin is left in the soul "_to be wrestled with_." The state of the case is this: The passions desire to be gratified without waiting for the sanction of reason, sometimes even in defiance of reason. Morally speaking, this is no evil. The passions are but blind instincts; it is the province of the will to restrain them in their proper limits, and to help her in this work she has reason and the grace of God. {384} If she fails to do her work, then she sins. Whenever sin is committed, it is the will that commits it. It is only the will that can sin. The sin lies not in the inordinate desire, but in the will's not resisting that desire. The will is the viceroy of God in the heart, appointed to keep that kingdom in peace. And herein lies the root of Christian morality, the secret of sanctification, and the essence of human probation. We speak of outward actions of sin; but all sin goes back to the will. There was the treason. "_Out of the heart_," says our Blessed Lord, "_proceed murders, adulteries, fornications, thefts, false testimonies, blasphemies_." [Footnote 130] [Footnote 130: St. Matt. xv. 19.] Each black deed is done in the secret chamber of the heart before the hand proceeds to execute it. Each false, impure, and blasphemous word is whispered first by the will before the lips utter it. Yes, man's heart is the battle-field. There is the scene of action. We speak sometimes of a man's being alone or being idle: why, a man is never alone; never idle. He may, indeed, be silent, his hands may be still, no one may be near him; but in that kingdom within great events are going on all the time. Angels and saints are there. The armies of Heaven and the armies of Hell meet there. Attack and repulse, parley and defiance, truce and surrender, stratagem and treason, victory and defeat--are things of daily occurrence there.