Superstition, blind obedience to custom, and the other substitutes for a
right and independent use of the mind, may accidentally and in some few
respects impress good ideas upon persons who are too darkened to accept
those ideas on their real merits. But then superstition itself is the
main cause of this very darkness. To hold error is in so far to foster
erroneous ways of thinking on all subjects; is to make the intelligence
less and less ready to receive truth in all matters whatever. Men are
made incapable of perceiving the rational defences, and of feeling
rational motives, for good habits,--so far as they are thus
incapable,--by the very errors which we are asked silently to
countenance as useful substitutes for right reason. 'Erroneous motives,'
as Condorcet has expressed this matter, 'have an additional drawback
attached to them, the habit which they strengthen of reasoning ill. The
more important the subject on which you reason ill, and the more you
busy yourself about it, by so much the more dangerous do the influences
of such a habit become. It is especially on subjects analogous to that
on which you reason wrongly, or which you connect with it by habit, that
such a defect extends most powerfully and most rapidly. Hence it is
extremely hard for the man who believes himself obliged to conform in
his conduct to what he considers truths useful to men, but who
attributes the obligation to erroneous motives, to reason very correctly
on the truths themselves; the more attention he pays to such motives,
and the more importance he comes to attach to them, the more likely he
will be to go wrong.'[9] So, in short, superstition does an immense harm
by enfeebling rational ways of thinking; it does a little good by
accidentally endorsing rational conclusions in one or two matters. And
yet, though the evil which it is said to repair is a trifle beside the
evil which it is admitted to inflict, the balance of expediencies is
after all declared to be such as to warrant us in calling errors useful!

III. A third objection now presents itself to me, which I wish to state
as strongly as possible. 'Even if a false opinion cannot in itself be
more useful than a true one, whatever good habits may seem to be
connected with it, yet,' it may be contended, 'relatively to the general
mental attitude of a set of men, to their other notions and maxims, the
false opinion may entail less harm than would be wrought by its mere
demolition. Th