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Page:Popular Science Monthly Volume 70.djvu/139

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"Poisons would seem as foods, foods as poisons; pleasures as sins, and sins as pleasures. The whole sanity and accuracy of life would be destroyed. For the security of action is conditioned by the exactness of our perceptions of the relations of external things and by the correctness of our reasoning in regard to these perceptions."

Mr. Grimshaw, falling back on the lore he had learned in school, said:

"In psychology the term reality is sometimes applied to a sense perception which is based on an outside influence acting then and there. In this sense the reality is not the external influence itself, but our direct or normal perception of it. Thus, the impression made by the sound of a gun would be a reality when the pressure' of air waves reached the brain, though the explosion may have taken place some seconds before. This reality as it comes to the brain should bear a definite relation to its source. In other words it must give the mind such information that the actual occurrence may be correctly interpreted. On its correct interpretation the fitness of our response in action must be conditioned. The term 'common sense' is applied to the normal working of these brain processes. An external stimulus produces a reality. The reality is transmitted to the brain where it is considered in its proper relations. Afterwards an impulse to action passes along the motor nerves to the muscles, which are the servants of the brain.

"In simple matters, as those pertaining to the apple, the dictates of common sense are obvious enough. The feelings are not moved by an apple, and our recognition of its nature is clouded by no illusions. But there are many relations in life in which 'common sense' does not find the problem so easy. If we examine the actions of ourselves and of our fellows, we shall find that the 'common sense' of different men does not act in parallel ways, and what seems to one wise or natural becomes grotesque or absurd to another."

Mr. Grimshaw then gave a number of illustrations of thought or action in which the 'common sense' may be deceived:

"You are in a railway train which is waiting on a side-track. Another train comes in sight, its motion seems transferred to your own train, but in the opposite direction. This motion continues until the other train has passed. It ceases suddenly, when you can almost feel the jolt of its stopping. But from other observations you know that your train has not moved in all this time.

"This is a simple illusion, easily corrected by the mind before it passes over into action. Let us look at some others. The story is told of a merchant who, smacking his lips over a glass of brandy, said to his clerk: 'The world looks very different to the man who has taken a good drink of brandy in the morning.' 'Yes,' said the clerk, 'and he looks different to the world, too.' Now, which is right? Is the world