Psychology and Ethnology. 135
psychology to the operator and his lantern. If a boy wants to know how moving pictures are produced, we expound to him the camera with which they are taken, the lantern with which they are projected on the screen, and the law by which retinal impressions fuse into one continuous sensation. But all this mechanism belongs to no particular time or place, but to any moving picture- show at any time in any part of the world, and it is continually in action from the beginning to the end of the film. Improvements may from time to time be made in the machinery, and these will be described in answer to the question why moving pictures are better now than they used to be. When, however, the boy wants to know why the hero of a particular film went up in an aeroplane, we do not go into the mechanism of the lantern and film, but merely tell him that it was to win the Sioo,ooo, without which the hard-hearted father would not allow him to marry his charming daughter. It does not follow that the mechanism does not cause the picture, but only that it is irrelevant.
Let epistemologists explain how it is possible to give two so utterly different and independent accounts of one event, one casual and universal, the other logical and particular, and both independent of one another, the fact remains. We can conceive a psychology of Parliament which would study the frame of mind of M.P.'s under the influence of collective deliberation and traditional party animus ; there are histories of debates in which each speech or repartee appears as the logical outcome of preceding statements and situations. A psychology of the stage would investigate the mentality of actors in general ; but it cannot explain the particular action of a player at a particular time ; that is conditioned by the logic of the play.
The logic of individual conduct is always approximate and unsatisfactory, because it is too indeterminate ; there