The importance of sense-perception need not be demonstrated. “If we ask,” says Mittermaier, “for the reason of our conviction of the truth of facts even in very important matters, and the basis of every judgment concerning existence of facts, we find that the evidence of the senses is final and seems, therefore, the only true source of certainty.” There has always, of course, been a quarrel as to the objectivity and reliability of sense-perception. That the senses do not lie, “not because they are always correct, but because they do not judge,” is a frequently quoted sentence of Kant’s; the Cyrenaics have already suggested this in asserting that pleasure and pain alone are indubitable. Aristotle narrows the veracity of sensation to its essential content, as does Epicurus. Descartes, Locke and Leibnitz have suggested that no image may be called, as mere change of feeling, true or false. Sensationalism in the work of Gassendi, Condillac, and Helvetius undertook for this reason the defense of the senses against the reproach of deceit, and as a rule did it by invoking the infallibility of the sense of touch against the reproach of the contradictions in the other senses. Reid went back to Aristotle in distinguishing specific objects for each sense and in assuming the truth of each sense within its own field. That these various theories can be adjusted is doubtful, even if, from a more conservative point of view, the subject may be treated quantitatively. The modern quantification of psychology was begun by Herbart, who developed a mathematical system of psychology by introducing certain completely unempirical postulates concerning the nature of representation and by applying certain simple premises in all deductions concerning numerical extent. Then came Fechner, who assumed the summation of stimuli. And finally these views were determined and fixed by the much-discussed Weber’s Law, according to which the intensity of the stimulus must increase in the proportion that the intensity of the sensation is to increase; i.e., if a stimulus of 20 units requires the addition of 3 before it can be perceived, a stimulus of 60 units would require the addition of 9. This law, which is of immense importance to criminalists who are discussing the sense-perceptions of witnesses, has been thoroughly and conclusively dealt with by A. Meinong.[173]