The one argument used by the Indeterminist against the Deterministic position with some degree of universality is that of the testimony of consciousness. It is the one to which practically all have appealed, and which all have flattered themselves was simple in nature and convincing in character. Professor Sidgwick, although he admitted that this testimony might be illusory, yet asserted "There is but one opposing argument of real force, namely, the immediate affirmation of consciousness in the moment of deliberate action." And by the testimony of consciousness must be meant, not, of course, a consciousness of acting, but that at the moment of acting we could, _under identical conditions_, have selected and acted upon an alternative that has been rejected. I emphasize the phrase "under identical conditions," because otherwise nothing is in dispute, and because, as we shall see, this important consideration has not been always or even frequently borne in mind. The question is, What does consciousness really tell us, and how far is its testimony valid? In some directions it must be admitted that the testimony of consciousness is absolute. In others it cannot, without verification, claim any authority whatever. When I say that I have a feeling of heat or coldness, of pleasure or pain, there is here a direct deliverance of consciousness against which there is no appeal. But consciousness does not and cannot tell me why I feel hot or cold, or what is the cause of a pain I am experiencing. In this last case the testimony of consciousness may be distinctly misleading. As it tells us nothing of the existence of a brain, a nervous system, viscera, etc., its testimony as to the cause of pain is obviously of no value. We are conscious of states of mind, and that is all. A man seized with sudden paralysis may be conscious of his power to move a limb, only to discover by experience his impotence. In short, consciousness cannot, indeed does not, tell us the causes of our states of mind. For this information we are thrown back upon observation, experiment, and experience. We must, then, make quite sure when we interrogate consciousness, exactly what it is that consciousness says, and whether what it says is on a subject that comes within its province.