Its keynote is to be found in the Protagorean " man is the measure."
The subordination of reason to a sense of superstitious fanaticism is the keynote of his character, and largely the explanation of his life.
Jevons arrived quite early in his career at the doctrines that constituted his most characteristic and original contributions to economics and logic. The theory of utility, which became the keynote of his general theory of political economy, was practically formulated in a letter written in 1860; and the germ of his logical principles of the substitution of similars may be found in the view which he propounded in another letter written in 1861, that "philosophy would be found to consist solely in pointing out the likeness of things."
The idea of re-birth was in the air; it was the very keynote of all the solemn initiations and mysteries - Mythraic, Orphic, Eleusinian - through which repentant pagans secured pardon and eternal bliss.