other kind of evidence. We frequently hesitate concerning the reports of
others. We balance the opposite circumstances, which cause any doubt or
uncertainty; and when we discover a superiority on any side, we incline
to it; but still with a diminution of assurance, in proportion to the
force of its antagonist.

89. This contrariety of evidence, in the present case, may be derived
from several different causes; from the opposition of contrary
testimony; from the character or number of the witnesses; from the
manner of their delivering their testimony; or from the union of all
these circumstances. We entertain a suspicion concerning any matter of
fact, when the witnesses contradict each other; when they are but few,
or of a doubtful character; when they have an interest in what they
affirm; when they deliver their testimony with hesitation, or on the
contrary, with too violent asseverations. There are many other
particulars of the same kind, which may diminish or destroy the force of
any argument, derived from human testimony.

Suppose, for instance, that the fact, which the testimony endeavours to
establish, partakes of the extraordinary and the marvellous; in that
case, the evidence, resulting from the testimony, admits of a
diminution, greater or less, in proportion as the fact is more or less
unusual. The reason why we place any credit in witnesses and historians,
is not derived from any _connexion_, which we perceive _a priori_,
between testimony and reality, but because we are accustomed to find a
conformity between them. But when the fact attested is such a one as has
seldom fallen under our observation, here is a contest of two opposite
experiences; of which the one destroys the other, as far as its force
goes, and the superior can only operate on the mind by the force, which
remains. The very same principle of experience, which gives us a certain