the greatest difference

[238] between assuming an opinion to be true, because with every
opportunity for contesting it it has not been refuted, and assuming its
truth for the purpose of not permitting its refutation. Complete liberty
of contradicting and disproving our opinion is the very condition which
justifies us in assuming its truth for purposes of action, and on no
other terms can a being with human faculties have any rational assurance
of being right."

(2) If the received opinion which it is sought to protect against the
intrusion of error is true, the suppression of discussion is still
contrary to general utility. A received opinion may happen to be true
(it is very seldom entirely true); but a rational certainty that it is
so can only be secured by the fact that it has been fully canvassed but
has not been shaken.

Commoner and more important is (3) the case where the conflicting
doctrines share the truth between them. Here Mill has little difficulty
in proving the utility of supplementing one-sided popular truths by
other truths which popular opinion omits to consider. And he observes
that if either of the opinions which share the truth has a claim not
merely to be tolerated but to be encouraged, it is the one which happens
to be held by the minority, since this is the one "which

[239] for the time being represents the neglected interests." He takes
the doctrines of Rousseau, which might conceivably have been suppressed
as pernicious. To the self-complacent eighteenth century those doctrines
came as "a salutary shock, dislocating the compact mass of one-sided
opinion." The current opinions were indeed nearer to the truth than
Rousseau's, they contained much less of error; "nevertheless there lay
in Rousseau's doctrine, and has floated down the stream of opinion along
with it, a considerable amount of exactly those truths which the popular
opinion wanted; and these are the deposit which we left behind when the
flood subsided."

Such is the drift of Mill's main argument. The present writer would
prefer to state the justification of freedom of opinion in a somewhat
different form, though in accordance with Mill's reasoning. The progress
of civilization, if it is partly conditioned by circumstances beyond
man's control, depends more, and in an increasing measure, on things
which are within his own power. Prominent among these are the
advancement of knowledge and the deliberate adaptation of his habits an