Metaphysics could find no answer to the question, because the latter, as stated by the former, does not admit of an answer. Scientific psychology--_i.e._, psycho-physiology--does not encounter the same difficulties. It does not take the finished ‘I’ of the adult, clearly conscious of himself, feeling himself distinctly opposed to the ‘not-I’ to the entire external world, but it goes back to the beginnings of this ‘I,’ investigates in what manner it is formed, and then finds that, at a time when the idea of the existence of a ‘not-I,’ would be really inexplicable, this idea, in fact, was absolutely non-existent, and that, when we do meet it, the ‘I’ has already had experiences which completely explain how it could and must arrive at the formation of the idea of a ‘not-I.’ We may assume that a certain degree of consciousness is the accompanying phenomenon of every reaction of the protoplasm on external action--_i.e._, is a fundamental quality of living matter. Even the simplest unicellular living organisms move with obvious intention towards certain goals, and away from certain points; they distinguish between foods and such materials as are unfit for nutrition; thus they have a species of will and judgment, and these two activities presuppose consciousness.[237] What may be the nature of this consciousness localized in protoplasm not yet even differentiated into nerve-cells, is a thing of which it is impossible for the human mind to form a definite idea. The only thing we can presuppose with any certainty is that in the crepuscular consciousness of a unicellular organism, the notion of an ‘I’ and a ‘not-I,’ which is opposed to it, does not exist. The cell feels changes in itself, and these changes provoke others, in accordance with established bio-chemical or bio-mechanical laws; it receives an impression to which it responds by a movement, but it has certainly no idea that the impression is caused by a process in the external world, and that its movement reacts on the external world. Even among animals very much higher in the scale, and considerably more advanced in differentiation, a consciousness of the ‘Ego,’ properly so called, is inconceivable. How can the ray of a star-fish, the bud of a tunicate, of a botryllus, the half of a double animal (diplozoon), the tube of an actinia, or of some other coral polypus, be aware of itself as a separate ‘I,’ seeing that, though it is an animal, it is at the same time a portion of a composite animal, of a colony of animals, and must perceive impressions which strike it directly, as well as those experienced by a companion of the same colony? Or can certain large worms, many of the species of Eunice, for example, have an idea of their ‘Ego,’ when they neither feel nor recognise portions of their own bodies as constituent parts of their individuality, and begin to eat their tails when, by any accident in coiling themselves, it happens to lie in front of their mouths?