Mathematical philosophy, a study of fate and freedom; lectures for educated laymen, by Cassius J. Keyser.

876 MATHEMATICAL PHILOSOPHY
In other departments, where investigation is more difficult, there is wide divergence in the results that have
been reported.
The Literature of the Law.-" Those," says James,
"who desire this dreadful literature can find it." The
best of it is cited under the caption, "Weber's Law,"
in the eleventh edition of The Encyclopedia Britannica.
For an excellent introduction to the methods of quantitative psychology, I have pleasure in referring to Titchener's
Experimental Psychology.
As to the Falidity of the Law.-In the nature of things,
no law can be shown to be absolutely valid by means of
experiment. Respecting Weber's Law, we may safely
make the following statements. Experiment has shown
it to be approximately valid in several of the chief departments of sense. As these are the departments most
accessible to experiment, it may be that the law will
yet be found to be approximately valid in other departments. Such validity has not been disproved for any
department. The law is found to hold best in the midregion of a sense scale; that is, it is least certain near the
initial and terminal thresholds. This fact, however, is
consistent with the assumption that the lawisequally valid
throughout the scale, for it is plain that, near the beginning and the end of a scale, where sensation is dim because
of defect or excess of stimulus, the distinctions of different sensations are more difficult to detect and record.
What is Measured.-Fechner calls the law of psychophysics a Maasformel. But what is it that is measured?
What is the magnitude? According to Fechner it is
sensation. He says:
Our measure of sensation amounts to this: that we
divide every sensation into equal parts, that is, into