Differences of illumination reveal a number of phenomena difficult to explain. Fechner calls attention to the appearance of stars: “At night everybody sees the stars, in daylight not even Sirius or Jupiter is seen. Yet the absolute difference between those places in the heavens where the stars are and the environing places is just as great as in the night--there is only an increase in illumination.” Of still greater importance to us is the circumstance noted but not explained by Bernstein. If, in daylight, we look into a basement room from outside, we can perceive nothing, almost; everything is dark, even the windows appear black. But in the evening, if the room is ever so slightly illuminated, and we look into it from outside, we can see even small articles distinctly. Yet there was much intenser light in the room in question during the day than the single illumination of the night could have provided. Hence, it is asserted, the difference in this case is a standard one. In open day the eye is accustomed to the dominating brightness of daylight, beside which the subdued illumination of the room seems relatively dark. But in the evening one is in the dark, and hence even the little light of a single candle is enough to enable one to see. That this explanation is untrue is shown by the fact that the phenomenon is not regulated even when the circumstances in question are made identical. If, for example, you approach the window in daylight with your eyes shut, lean your forehead against the pane and shut out the light on the sides with your hands, and then open your eyes, you see as little in the room as when you looked into it without performing this ceremony. So again, if during the night you gazed at some near-by gas lamp and then glanced into the room, there is only a few moments’ indistinctness at most, after that the single candle is enough. The reason, then, must be different from the assigned one--but whatever it is, we need only to maintain that immediate judgment concerning numerous cases involving situations of this kind would be overhasty. It is often said that a witness was able to see this or that under such and such illumination, or that he was unable to see it, although he denies his ability or inability. The only solution of such contradictions is an experiment. The attempt must be made either by the judge or some reliable third person, to discover whether, under the same conditions of illumination, anything could be seen at the place in question or not.