t a given time, so that
successive tentative descriptions of a phenomenon, got by guessing till
a guess is found which tallies with the facts, may, though conflicting
(e.g. the theories respecting the motions of the heavenly bodies), be
_all_ correct _so far as they go_. Induction is proof, the inferring
something unobserved from something observed; and to provide a proper
test of proof is the special purpose of inductive logic. But colligation
simply sums up the facts observed, as seen under a new point of view.
Dr. Whewell contends that, besides the sum of the facts, colligation
introduces, as a principle of connection, a conception of the mind not
existing in the facts. But, in fact, it is only because this conception
is a copy of something in the facts, although our senses are too weak to
recognise it directly, that the facts are rightly classed under the
conception. The conception is often even got by abstraction from the
facts which it colligates; but also when it is a hypothesis, borrowed
from strange phenomena, it still is accepted as true only because found
actually, and as a fact, whatever the origin of the knowledge of the
fact, to fit and to describe as a whole the separate observations. Thus,
though Kepler's consequent inference that, _because_ the orbit of a
planet is an ellipse, the planet would _continue_ to revolve in that
same ellipse, was an induction, his previous application of the
conception of an ellipse, abstracted from other phenomena, to sum up his
direct observations of the successive positions occupied by the
different planets, and thus to describe their orbits, was no induction.
It altered only the _predicate_, changing--The successive places of,
e.g. Mars, are A, B, C, and so forth, into--The successive places of,
e.g. Mars, are points in an ellipse: whereas induction always widens the
_subject_.

CHAPTER III.

THE GROUND OF INDUCTION.

Induction is generalisation from experience. It assumes, that whatever
is true in any one case, is true in all cases of a certain description,
whether past, present, or future (and not merely in future cases, as is
wrongly implied in the statement by Reid's and Stewart's school, that
the principle of induction is 'our intuitive conviction that the future
will resemble the past'). It assumes, in short, that the course of
nature is uniform, that is, that all things take place according to
general laws. But this general axiom of induction, though by