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

THE MATHEMATICS OF PSYCHOLOGY 401
Du Bois-Reymond, where the chief ideas of the latter
are presented and his works cited.
Conquest or Transcendence of Sensibility Thresholds.By way of emphasis,-for the matter is very important,
especially for psychology,-let us state explicitly that the
conceptual continua which we have been discussing at so
great length are not infected, as are sense "continua,"
with the presence of thresholds. They are free from
initial thresholds, for any such conceptual continuum
is composed of parts that continuously decrease in size
down to zero. They are free from terminal thresholds
because they each of them present a sequence of parts
increasing beyond any assigned finite amount, however
great. They are free from difference thresholds, for any
difference, however small, between portions of a conceptual continuum is conceptually discernible. In a
sense " continuum " there are, properly speaking, neither
infinitesimals nor infinites, but in a conceptual continuum there are both. In a word we may say that
conception, or thought, is a kind of infinitely refined sensibility, for there is no quantity too small for thought to
detect and to discriminate from any other. Here this
lecture must close. Our topic has been the mathématics of
psychology; the discussion, you see, has inevitably led
us pretty far into our next topic-the psychology of
mathematics-and even into the psychology of science
in general.