The ego is a Latin term used in philosophical language to denote the pronoun “I,” and the pronoun “I” is quite a definite nerve-structure situated in quite a definite place of the centre of language. As all words, so also the term “I” is a symbol. Its general meaning is unequivocal; it stands for the name of the speaker. It stands for Mr. Brown, if Mr. Brown speaks of himself, for Mr. Smith, if Mr. Smith speaks of himself, etc. What does Mr. Brown mean when he says, “_I_ speak, _I_ act, _I_ will, _I_ feel pain, _I_ feel pleasure, _I_ intend,” etc.? When Mr. Brown speaks, a certain number of word-structures in the centre of language are in a state of commotion, innervating the muscles of speech. Correspondent to this physiological process, a state of consciousness obtains, which is an awareness of the situation. When he adds: “I say this,” it is again a special nerve-structure that is irritated into action and he might just as well say: “Mr. Brown says this.” The idea of Mr. Brown, viz. of his own personality, is just as much an idea as his idea of Mr. Smith. The main difference consists in the fact that the idea of one’s own personality is very much more important than the ideas representing other personalities. The nervous structure representing the feeling of the idea “I” must be the centre of innumerable nervous tracts connecting it with all those activities which when performed are thought of as done by ourselves. The “I do this” is almost constantly ready to fill the present state of consciousness and to accompany any action performed through the innervation of other brain structures. Sentient substance is not always actually feeling. It is feeling only when in a state of extra-commotion. Systems of sentient substance are called organisms; all its structures are interconnected and most so those structures in which sentiency as well as motory impulses are differentiated—viz. the nervous structures. The extra-commotions which agitate the different nervous structures, the memories of former sense-perceptions, of sounds, of words, of ideas depend upon the conditions of the moment. Now this and now another structure will represent the summit of commotion and the feeling of the strongest commotion at a given time will under normal conditions appear as the contents of consciousness. It is as it were the focus in which the attention of the whole organism is centralised. That which appears in the focus is clear and distinct, while the other weaker feelings rapidly disappear into the undistinguishable general feeling of the organism as a whole, commonly called cœnæsthesis or _Gemeingefühl_.