Elements of the philosophy of the human mind. By Dugald Stewart. Rev. and abridged, with critical and explanatory notes, for the use of colleges and schools. By Francis Bowen ...

REASONING AND DEDUCTIVE EVIDENCE. 489
But although, in philosophical language, the epithet probable
be applied to events which are acknowledged to be certain, it is
also applied to those events which are called probable by the
vulgar. The philosophical meaning of the word, therefore, is
more comprehensive than the popular; the former denoting
that particular species of evidence of which contingent truths
admit; the latter being confined to such degrees of this evidence
as fall short of the highest. These different degrees of probability the philosopher considers as a series, beginning with bare
possibility, and terminating in that apprehended infallibility with
which the phrase moral certainty is synonymous. To this last
term of the series, the word-probable is, in its ordinary acceptation, plainly inapplicable.
The satisfaction which the astronomer derives from the exact
coincidence, in point of time, between his theoretical predictions
concerning the phenomena of the heavens, and the corresponding events when they actually occur, does not imply the smallest
doubt, on his part, of the constancy of the laws of nature. It
resolves partly into the pleasure of arriving at the knowledge
of the same truth or of the same fact by different media; but
chiefly into the gratifying assurance which he thus receives, of
the correctness of his principles, and of the competency of the
human faculties to these sublime investigations. What exquisite delight must La Place have felt, when, by deducing from
the theory of gravitation the cause of the acceleration of the
moon's mean motion —an acceleration which proceeds at the
rate of little more than 11 in a century, - he accounted, with
such mathematical precision, for all the recorded observations
of the place from the infancy of astronomical science! It is
fiom the length and abstruseness, however, of the reasoning
process, and from the powerful effect produced on the imagination, by a calculus which brings into immediate contrast with
the immensity of time such evanescent elements as the fractional parts of a second, that the coincidence between the computation and the event appears in this instance so peculiarly
striking. In other respects, our confidence in the future result