Essays on the Foundation and Publication of Opinions, and on other Subjects. Essays of the Pursuit of Truth, on the Progress of Knowledge, and the Fundamental Principles of all Evidence and Expectation. [pp. 394-428]

and Pursuit o'f'Truth.
that the circumstance of the ice remaining unmelted, rests on the
concurrent testimony of a great number of people-people, too, of
reputation, science, and perspicacity, who had no motive for false hood, who had discernment to perceive, and honesty to tell the
truth, and whose interests would essentially suffer from any de parture from veracity. Under such circumstances it may be
allowed, false testimony is impossible.
"Now mark the principle on which this representation pro ceeds. Let us consider the positions, that what is attested by a
great number of witnesses must inevitably be true,-that people
of reputation and intelligence, without any apparent motive for
falsehood, are invariably accurate in their testimony-and that
they are, above all, incapable of violating the truth, when a want of
veracity would be ruinous to their own interests. Granting all
this, I ask the objector, how he knows these things are so: that
men of character and in these circumstances speak the truth?
He will reply, that he has invariably found them to act in this
mannel: but why because you have found them to act in this
manner in a few or even in many cases within your own expe rience, or in the experience of ages, do you conclude, that they
have acted so in all cases, and in the case before us? The only
answer, is, that it is impossible Ah to take it for granted, that in
precisely similar circumstances, similar results will ensue, or that
like causes have always like effects.
"Thus, on the ground of the uniformity of causation, he would
be maintaining the competency of testimony to prove a fact,
which implies a deviation from that uniformity.
Again,
"These considerations appear to establish the important rule,
that no testimony can prove any deviation from the known sequences of cause and effect, or that, at any time, similar effects have
not had similar causes, or similar causes similar effects.
" In the strongest conceivable case, the argument of an advocate for the power of testimony to favour such deviations, would
be this:'It is impossible that human testimony should not be
true in these circumstances, because its falsity would be contrary
to the principles of human nature; that is, it would imply a deviation from that sequence of motives and voluntary actions which
has invariably been observed.'
"But, on precisely the same ground he ought to maintain, that
the circumstances attested could not take place, because they are
contrary to the laws of the material world, unless it can be shown,
as I have before remarked, that the certainty or uniformity of
causation in voluntary actions, is greater than in physical events.
"The rule now laid down is, that in fact, that by which man.
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