opinions may be wrong, we should leave all our interests uncared
for, and all our duties unperformed. An objection which applies to all
conduct can be no valid objection to any conduct in particular. It
is the duty of governments, and of individuals, to form the truest
opinions they can; to form them carefully, and never impose them
upon others unless they are quite sure of being right. But when they
are sure (such reasoners may say), it is not conscientiousness but
cowardice to shrink from acting on their opinions, and allow doctrines
which they honestly think dangerous to the welfare of mankind,
either in this life or in another, to be scattered abroad without
restraint, because other people, in less enlightened times, have
persecuted opinions now believed to be true. Let us take care, it
may be said, not to make the same mistake: but governments and nations
have made mistakes in other things, which are not denied to be fit
subjects for the exercise of authority: they have laid on bad taxes,
made unjust wars. Ought we therefore to lay on no taxes, and, under
whatever provocation, make no wars? Men, and governments, must act
to the best of their ability. There is no such thing as absolute
certainty, but there is assurance sufficient for the purposes of human
life. We may, and must, assume our opinion to be true for the guidance
of our own conduct: and it is assuming no more when we forbid bad
men to pervert society by the propagation of opinions which we
regard as false and pernicious.

  I answer, that it is assuming very much more. There is the
greatest difference between presuming 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.

  When we consider either the history of opinion, or the ordinary
conduct of human life, to what is it to be ascribed that the one and
the other are no worse than they are? Not certainly to the inherent
force of the human understanding; for, on any matter not self-evident,
there are ninety-nine persons totally incapable of judging of it for
one who is capable; and the capacity of the hundredth person is only
comparative; for the majority of the eminent men of every past
generation held many opinions now known to be erroneous, and did or
approved numerous things which no one will now justify. Why is it,
then, that there is on the whole a preponderance among mankind of
rational opinions and rational conduct? If there really is this
preponderance- which there must be unless human affairs are, and have
always been, in an almost desperate state- it is owing to a quality
of the human mind, the source of everything respectable in man
either as an intellectual or as a moral being, namely, that his errors
are corrigible. He is capable of rectifying his mistakes, by
discussion and experience. Not by experience alone. There must be
discussion, to show how experience is to be interpreted. Wrong
opinions and practices gradually yield to fact and argument; but facts
and arguments, to produce any effect on the mind, must be brought
before it. Very few facts are able to tell their own story, without
comments to bring out their meaning. The whole strength and value,
then, of human judgment, depending on the one property, that it can be
set right when it is wrong, reliance can be placed on it only when the
means of setting it right are kept constantly at hand. In the case
of any person whose judgment is really deserving of confidence, how
has it become so? Because he has kept his mind open to criticism of
his opinions and conduct. Because it has been his practice to listen
to all that could be said against him; to profit by as much of it as
was just, and expound to himself, and upon occasion to others, the
fallacy of what was fallacious. Because he has felt, that the only way
in which a human being can make some approach to knowing the whole
of a subject, is by hearing what can be said about it by persons of
every variety of opinion, and studying all modes in which it can be
looked at by every character of mind. No wise man ever acquired his
wisdom in any mode but this; nor is it in the nature of human
intellect to become wise in any other manner. The steady habit of
correcting and completing his own opinion by collating it with those
of others, so far from causing doubt and hesitation in carrying it
into practice, is the only stable foundation for a just reliance on
it: for, being cognisant of all that can, at least obviously, be
said against him, and having taken up his position against all
gainsayers- knowing that he has sought for objections and
difficulties, instead of avoiding them, and has shut out no light
which can be thrown upon the subject from any quarter- he has a right
to think his judgment better than that of any person, or any
multitude, who have not gone through a similar process.

  It is not too much to require that what the wisest of mankind, those
who are best entitled to trust their own judgment, find necessary to
warrant their relying on it, should be submitted to by that
miscellaneous collection of a few wise and many foolish individuals,
called the public. The most intolerant of churches, the Roman Catholic
Church, even at the canonisation of a saint, admits, and listens
patiently to, a "devil's advocate." The holiest of men, it appears,
cannot be admitted to posthumous honours, until all that the devil
could say against him is known and weighed. If even the Newtonian
philosophy were not permitted to be questioned, mankind could not feel
as complete assurance of its truth as they now do. The beliefs which
we have most warrant for have no safeguard to rest on, but a
standing invitation to the whole world to prove them unfounded. If the
challenge is not accepted, or is accepted and the attempt fails, we
are far enough from certainty still; but we have done the best that
the existing state of human reason admits of; we have neglected
nothing that could give the truth a chance of reaching us: if the
lists are kept open, we may hope that if there be a better truth, it
will be found when the human mind is capable of receiving it; and in