Heraclitus, who recommends this research, asserts that "there are
necessary changes of contraries into each other;" he speaks of
"ascenscions" and of a "descent," says that it is "a rest to change,
a fatigue to continue unremittingly in the same kinds of work, and to
be overwrought. He thus reduces us to conjectures because he does not
explain himself definitely; and he would even force us to ask how he
himself came to discover what he propounds.