Take such a sentence as this: African explorers are subject to fevers which cause restlessness and delirium. Note the expression, "cause restlessness." _Restlessness has a cause_. Clearly, then, any one who wished to get rid of restlessness would proceed at once to deal with the cause. If that were not removed, a doctor might prescribe a hundred things, and all might be taken in turn, without producing the least effect. Things are so arranged in the original planning of the world that certain effects must follow certain causes, and certain causes must be abolished before certain effects can be removed. Certain parts of Africa are inseparably linked with the physical experience called fever; this fever is in turn infallibly linked with a mental experience called restlessness and delirium. To abolish the mental experience the radical method would be to abolish the physical experience, and the way of abolishing the physical experience would be to abolish Africa, or to cease to go there. Now this holds good for all other forms of Restlessness. Every other form and kind of Restlessness in the world has a definite cause, and the particular kind of Restlessness can only be removed by removing the allotted cause. All this is also true of Rest. Restlessness has a cause: must not _Rest_ have a cause? Necessarily. If it were a chance world we would not expect this; but, being a methodical world, it cannot be otherwise. Rest, physical rest, moral rest, spiritual rest, every kind of rest has a cause, as certainly as restlessness. Now causes are discriminating. There is one kind of cause for every particular effect, and no other; and if one particular effect is desired, the corresponding cause must be set in motion. It is no use proposing finely devised schemes, or going through general pious exercises in the hope that somehow Rest will come. The Christian life is not casual but causal. All nature is a standing protest against the absurdity of expecting to secure spiritual effects, or any effects, without the employment of appropriate causes. The Great Teacher dealt what ought to have been the final blow to this infinite irrelevancy by a single question, "Do men gather grapes of thorns or figs of thistles?" Why, then, did the Great Teacher not educate His followers fully? Why did He not tell us, for example, how such a thing as Rest might be obtained? The answer is, that _He did_. But plainly, explicitly, in so many words? Yes, plainly, explicitly, in so many words. He assigned Rest to its cause, in words with which each of us has been familiar from his earliest childhood. He begins, you remember--for you at once know the passage I refer to--almost as if Rest could be had without any cause: "Come unto me," He says, "and I will _give_ you Rest."