The difficulty described is especially felt in the following considerations. In the complex _A B C_ ... which we have designated as the material world, we find as part, not only our own body _K L M_ ..., but also the bodies of other persons (or animals) _K' L' M'_ ..., _K" L" M"_ ..., annexed to which, after the analogy of the complex α β γ ..., we conceive similar α' β' γ' ..., α" β" γ". As long as we deal with _K' L' M'_ ..., we find ourselves in a thoroughly familiar province, at every point sensorially accessible to us. But when we inquire after the sensations or feelings that belong to the body _K' L' M'_ ..., we no longer find in the province of sense the elements we seek: but we add them in thought. Not only is the domain into which we now enter much less familiar to us, but also the transition to it is relatively unsafe. We are possessed of a feeling as if we were about to plunge into an abyss. They that always pursue this direction of thought and this direction _only_, will never get completely rid of the feeling of insecurity that is very productive as a source of apparent problems. But we are not limited to this way of reasoning. Let us consider first the reciprocal relation of the elements of the complex _A B C_ ..., without regarding _K L M_ ... (our body). Every physical investigation is of this kind. A white bullet falls upon a bell; a sound is heard. The bullet turns yellow before a sodium lamp, red before a lithium lamp. Here the elements (_A B C_ ...) appear to be connected only _among each other_ and to be independent of our body (_K L M_ ...). But if we take santonine the bullet turns yellow again. If we turn one eye sidewise we see two bullets. If we close our eyes entirely we see no bullet at all. If we sever our auditory nerve no sound is heard. The elements _A B C_ ..., therefore, are not only connected among each other, but also with _K L M_. To this extent and to this extent _only_ do we call _A B C_ ... _sensations_, and regard _A B C_ ... as belonging to the ego. In this way, accordingly, we do not meet with the gap between bodies and sensations before described, between that which is without and that which is within, between the material and the spiritual world.[19] All elements _A B C_ ... _K L M_ ... constitute but _one single_ coherent mass, which when any one element in it is disturbed _all_ is put in motion; except that a disturbance has a more extensive and profound action in _K L M_ ..., than in _A B C_. A magnet in our neighborhood disturbs the particles of iron near it; a falling boulder shakes the earth; but the severing of a nerve sets in motion the _entire_ system of elements. Quite involuntarily does this relation of things suggest the picture of a viscous mass, at certain places (as in the ego) more firmly coherent than at others. [19] Compare my _Grundlinien der Lehre von den Bewegungsempfindungen_. Leipsic, Engelmann, 1875, p. 54. * * * * *