“It is,” says Huxley,[198] “experimentally demonstrable--any one who cares to run a pin into himself may perform a sufficient demonstration of the fact--that a mode of motion of the nervous system is the immediate antecedent of a state of consciousness. We have as much reason for regarding the mode of motion as the cause of the state of consciousness, as we have for regarding any event as the cause of another. How the one phenomenon causes the other we know as much, or as little, as in any other case of causation; but we have as much right to believe that the sensation is an effect of the molecular change, as we have to believe that motion is an effect of impact; and there is as much propriety in saying that the brain evolves sensation, as there is in saying that an iron rod, when hammered, evolves heat.” But if we speak of the related antecedent as the cause, it is not obvious why we should not describe the desire to demonstrate the supposed fact as the cause of running in the pin. We seem to have just as much reason for calling this antecedent state of consciousness the cause of certain movements and behaviour, as of calling a mode of motion in the brain the cause of a further state of consciousness. It is true that we have not the least idea how the desire can cause the act; but Huxley practically admits that we have no idea how molecular change can be the cause of consciousness. In the one case we are no worse off than we are in the other. Neither position is logically defensible; since each assumes that physical events and states of consciousness can constitute links in the same causal chain.