feeling of self-love or
self-interest--this operates in much more subtle ways than most people
imagine, in ways so subtle that the self-deceiver, however honest,
would fail to be conscious of the influence if it were pointed out to
him. When the slothful man saith, There is a lion in the path, we can
all detect the bias to his belief, and so we can when the slothful
student says that he will work hard to-morrow, or next week, or next
month; or when the disappointed man shows an exaggerated sense of
the advantages of a successful rival or of his own disadvantages. But
self-interest works to bias belief in much less palpable ways than
those. It is this bias that accounts for the difficulty that men of
antagonistic interests have in seeing the arguments or believing
in the honesty of their opponents. You shall find conferences
held between capitalists and workmen in which the two sides, both
represented by men incapable of consciously dishonest action, fail
altogether to see the force of each other's arguments, and are
mutually astonished each at the other's blindness.

_The Bias of Custom._

That custom, habits of thought and practice, affect belief, is also
generally acknowledged, though the strength and wide reach of the bias
is seldom realised. Very simple cases of unreasoning prejudice were
adduced by Locke, who was the first to suggest a general explanation
of them in the "Association of Ideas" (_Human Understanding_, bk. ii.
ch. xxxiii.). There is, for instance, the fear that overcomes many
people when alone in the dark. In vain reason tells them that there is
no real danger; they have a certain tremor of apprehension that they
cannot get rid of, because darkness is inseparably connected in
their minds with images of horror. Similarly we contract unreasonable
dislikes to places where painful things have happened to us. Equally
unreasoning, if not unreasonable, is our attachment to customary
doctrines or practices, and our invincible antipathy to those who do
not observe them.

Words are very common vehicles for the currency of this kind of
prejudice, good or bad meanings being attached to them by custom. The
power of words in this way is recognised in the proverb: "Give a dog
a bad name, and then hang him". These verbal prejudices are Bacon's
_Idola Fori_, illusions of conversation. Each of us is brought up in a
certain sect or party, and accustomed to respect or dishonour
certain sectarian or party names, Wh