Of all the dangerous mental habits, that which schoolboys call
"cocksureness" is probably the most perilous; and the inestimable
value of metaphysical discipline is that it furnishes an effectual
counterpoise to this evil proclivity. Whoso has mastered the elements
of philosophy knows that the attribute of unquestionable certainty
appertains only to the existence of a state of consciousness so long as
it exists; all other beliefs are mere probabilities of a higher or lower
order. Sound metaphysic is an amulet which renders its possessor proof
alike against the poison of superstition and the counter-poison of
shallow negation; by showing that the affirmations of the former and the
denials of the latter alike deal with matters about which, for lack of
evidence, nothing can be either affirmed or denied.