If this antagonism is substantial it is serious; for Natural Philosophers will not be willing to concede fundamental inaccuracy or uncertainty about their recognised and long-established laws of motion, when applied to ordinary matter; nor will they be prepared to tolerate any the least departure from the law of the conservation of energy, when all forms of energy are taken into account. Hence, if guidance and control can be admitted into the scheme by no means short of undermining and refuting those laws, there may be every expectation that the attitude of scientific men will be perennially hostile to the idea of guidance or control, and so to the efficacy of prayer, and to many another practical outcome of religious belief. It becomes therefore an important question to consider whether it is true that life or mind is incompetent to disarrange or interfere with matter at all, except as itself an automatic part of the machine,—whether in fact it is merely an ornamental appendage or phantasmal accessory of the working parts. Now experience—the same kind of experience as gave us our scheme of mechanics—shows us that to all appearance live animals certainly can direct and control mechanical energies to bring about desired and preconceived results; and that man can definitely will that those results shall occur. The way the energy is provided is understood, and its mode of application is fairly understood; what is not understood is the way its activity is _determined_. Undoubtedly our body is material and can act on other matter; and the energy of its operations is derived from food, like any other self-propelled and fuel-fed mechanism; but mechanism is usually controlled by an attendant. The question is whether our will or mind or life can direct our body's energy along certain channels to attain desired ends, or whether—as in a motor-car with an automaton driver—the end and aim of all activity is wholly determined by mechanical causes. And a further question concerns the mode whereby vital control, if any, is achieved. Answers that might be hazarded are: (_a_) That life is itself a latent store of energy, and achieves its results by imparting to matter energy that would not otherwise be in evidence: in which case life would be a part of the machine, and as truly mechanical as all the rest. Experiment lends no support to this view of the relation between life and energy, and I hold that it is false; because the essential property of energy is that it can transform itself into other forms, remaining constant in quantity, whereas life does not add to the stock of any known form of energy, nor does death affect the sum of energy in any known way.