If there is anything in the world you feel sure of, it is that you can depend upon
the "evidence of your own senses," eyes, ears, nose, etc. You rest serene in the conviction that your senses picture the world to you exactly as it is. It is a common saying that "Seeing is believing."
Should Seeing Be Believing?
Yet how can you be sure that any object in the external world is actually what your sense-perceptions report it to be?
You have learned that a countless number of physical agencies must intervene before your mind can receive an impression or message through any of the senses.
Under these conditions you cannot be sure that your impression of a green lamp-shade, for instance, comes through the same sort of etheric and cellular activities
that convey a picture of the same lamp-shade to the brain of another. If the physical agencies through which your sense-impressions of the lamp-shade filter are not identical with the agencies through which they pass to the other person's brain, then your mental picture and his mental picture cannot be the same. You can never be sure that what both you and another may describe as green may not create an entirely different impression in your mind from the impression it creates in his.
Other facts add to your uncertainty. Thus, the same stimulus acting on different organs of sense will produce different sensations. A blow upon the eye will cause you to "see stars"; a similar blow
upon the ear will cause you to hear an explosive sound. In other words, the vibratory effect of a touch on eye or ear is the same as that of light or sound vibrations.
Hearing the Lightning