Page:Popular Science Monthly Volume 13.djvu/188

176 success of jugglery and all the forms of tricks of sleight-of-hand; audiences fancy themselves to be seeing what they do not see. Casting our eyes upward to the sun and moon and stars, these heavenly objects seem to move with measurable slowness across the concave surface of the blue arch of sky; and only through the deductive reasonings and calculations of a Copernicus, a Galileo, a Newton, are we brought to the conviction that the earth is the moving object, that the blue vault but marks in the air the limitations of our vision, and that the shining stars that appear as candles in the sky are gigantic worlds moving with enormous velocity millions of miles away. Sitting in a railway-train at a station, as the train next to us on one side begins to move, we seem ourselves to be in motion, and only by looking on the opposite side and steadily observing some point or object that by previous observation we know to be fixed, can we correct our delusion; but in practical life we are not always able to find a fixed point or object external to ourselves by which we can distinguish the subjective and objective in our retinal impressions. Thus, in all human experience, "truth and lies are faced alike; their port, taste, and proceedings, are the same; we look upon them with the same eyes."

—But the most serious blunders of the sense of sight, or indeed of the other senses, and indeed of reasoning in general, come from confounding the subjective with the objective. In certain states of the system, which are not rare but very common, and which may be either temporary or permanent, the brain has the power not only of modifying the impressions made by external objects over the retina, but of originating impressions even when there are no external objects corresponding to those impressions, and the individuals may have no way of distinguishing subjective from objective visions, or find it very difficult to do so without outside aid.