The same alternation between energy of motion and of position takes place in all rhythmical movements such as waves, which, whether in water, air, or ether, are propagated, as in the case of the pendulum, by particles forced out of their position of rest and oscillating between the two energies.
Thus if waves run along an elastic wire A B, the particle P, which has been forced into the position p, oscillates backwards and forwards between p and q, beginning with nothing but energy of position at p, losing it all for energy of motion at P, and regaining it at q. All wave-motions therefore—that is to say, all sound, light, and heat—depend on this primitive polarity.
If we have got this definition of the two forms of energy clearly into our heads, we shall be the better prepared for this further generalisation—the grandest, perhaps, in the whole range of modern science—that energy, like matter, is indestructible, and can only be transformed, but never created or annihilated.
This is at first sight a more difficult proposition to establish in the case of energy than in that of matter. In the latter case we have nothing in our experience that can lead us to suppose that we have ever created something out of nothing; but in the former, our first impression undoubtedly is that we do create force. If I throw a stone at a bird I have an instinctive impression that the force which projects the stone is the creation of my own conscious will; that I had the choice either to throw or not to throw; and that if I had decided not to throw, the impelling force would never have existed. But, if we look more closely at the matter, it is not really so. The chain of events is this: the first impulse proceeds from the visual rays, which, concentrated by the lens of the eye on the retina, give an image of the bird; this sends vibrations along the optic nerve to the brain, setting in motion certain molecules of that organ; these again send vibrations along other nerves to certain muscles of the arm and hand, which contract, and by doing so give out the energy of movement which throws the stone. All this process is strictly mechanical; the eye acts precisely like a camera obscura in forming the image; the nerve-vibrations, though not identical with those of the wires of an electric telegraph, are of the same nature, their velocity can be measured, and their presence detected by the galvanometer; the energy of the muscle is stored there by the slow combustion of the food we have eaten, in the oxygen of the air we have breathed. Take any of these conditions away, and no effort of the will can produce the result. If the nerve is paralysed, or the muscle, from prolonged starvation, has no energy left, the stone will not be thrown, however much we may desire to kill the bird.
Again, precisely the same circle of events takes place in numerous instances without any intervention of this additional factor of conscious will. We breathe mechanically, the muscles of the chest causing it to rise and fall like the waves of the ocean, without any deliberate intention of taking air into the lungs and exhaling it. Nay more, there are instances of what was at first accompanied by the sensation of conscious will, ceasing to be so when the molecular movements had made channels for themselves, as when a piano-player, who had learned his notes with difficulty, ends by playing a complicated piece automatically. The case of animals also raises another difficulty. Suppose a retriever dog sees his master shoot at and miss a hare: shall he obey the promptings of his animal instinct and give chase, or those of his higher moral nature which tell him that it is wrong to do so without the word of command? It is hard to see how this differs from the case of a man resisting or yielding to temptation; and how, if we assign conscious will to the man, we can deny it to the dog.
Reasoning from these premises, some philosophers have come to the conclusion that man and all animals are but mechanical automata, cleverly constructed to work in a certain way fitting in with the equally preordained course of outward phenomena; and that the sensation of will is merely an illusion arising as a last refinement in the adjustment of the machinery. But here comes in that principle of duality or polarity, by which a proposition may be at once true and untrue, and two contradictory opposites exist together. No amount of philosophical reasoning can make us believe that we are altogether machines and not free agents; it runs off us like water from a duck’s back, and leaves us in presence of the intuitive conviction that to a great extent
Man is man and master of his fate.
If this be an illusion, why not everything—evidence of the senses, experiment, natural law, science, as well as morality and religion?