Theories for truths, fable for fact

Theories for truths, fable for fact; system for science vex the thought Life’s one great lesson you despise— to know that all we know is nought.

This is in fact:—

Well didst thou say, Athena’s noblest son, The most we know is nothing can be known.

The next is:—

Essence and substance, sequence, cause, beginning, ending, space and time, These be the toys of manhood’s mind, at once ridiculous and sublime.