The glass placed in the middle of the table stops the movement because it drives away the fluid. The glass placed on one side of the table makes the opposite side rise because the fluid, fleeing from the glass, accumulates there. Thury does not attempt the discussion of this theory. But we may repeat with Gasparin, "When you shall have explained to me how I lift my hand, I will explain to you how I cause the leg of the table to rise." The whole problem lies in that,--the action of mind on matter. We must not dream that we can give a final solution of it at the present time. To reduce the new facts to conformity with the old ones; that is to say, to relate the action of mind upon inert bodies outside of us to the action of mind upon the matter in our bodies--such is the only problem which the science of to-day can reasonably propose to itself. Thury states it in general terms as follows: _General Question of the Action of Mind upon Matter._--We shall seek to formulate the results of experiment up to the point where experiment abandons us. From there on we shall study all the alternatives offered to our mind, as simple possibilities, some of which will give place to hypotheses explanatory of the new phenomena. _First principle: In the ordinary state of the body, the will acts directly only in the sphere of the organism._--Matter belonging to the external world is modified _on contact with the organism_, and the modifications which it undergoes gradually produce others by contiguity. It is thus that we can act upon objects at a distance from us. Our action at a distance upon all that surrounds us is _mediate_ and not immediate. We believe that this is true of the action of all physical forces, such as gravity, heat, electricity. Their effect is gradually communicated, and thus alone they put distance behind them and come into relation with man as a sentient being. _Second principle: In the organism itself there is a series of mediate acts._--Thus the will does not act directly upon the bones which receive the movement of the muscles; nor does the will modify any more directly the muscles, since, when deprived of nerves, they are incapable of movement. Does the will act directly upon the nerves? It is a mooted question whether it modifies them directly or indirectly. Thus the substance upon which the soul immediately acts is still undetermined. The substance may be solid, may be fluid; it may be a substance still unknown, or perhaps a particular state of known substances. In order to avoid a circumlocution, let me give it a name. I shall call it the _psychode_ ([Greek: psyche], soul, and [Greek: odos], way).