other earthwards, there is only theoretical elimination
of either tendency, considered as counteracting the other; and this is
more specifically called the _Resolution_ or Analysis of the total
effect into its component conditions. Now, Elimination and Resolution
may be said to be the essential process of Induction in the widest sense
of the term, as including the combination of Induction with Deduction.

The several conditions constituting any cause, then, by aiding or
counteracting one another's tendencies, jointly determine the total
effect. Hence, viewed in relation one to another, they may be said to
stand in _Reciprocity_ or mutual influence. This relation at any moment
is itself one of co-existence, though it is conceived with reference to
a possible effect. As Kant says, all substances, as perceived in space
at the same time, are in reciprocal activity. And what is true of the
world of things at any moment (as connected, say, by gravity), is true
of any selected group of circumstances which we regard as the particular
cause of any event to come. The use of the concept of reciprocity, then,
lies in the analysis of a cause: we must not think of reciprocity as
obtaining in the succession of cause and effect, as if the effect could
turn back upon its cause; for as the effect arises its cause disappears,
and is irrecoverable by Nature or Magic. There are many cases of
rhythmic change and of moving equilibria, in which one movement or
process produces another, and this produces something closely resembling
the former, and so on in long series; as with the swing of a pendulum or
the orbit of a planet: but these are series of cause and effect, not of
reciprocity.

CHAPTER XV

INDUCTIVE METHOD

Sec. 1. It is necessary to describe briefly the process of investigating
laws of causation, not with the notion of teaching any one the Art of
Discovery, which each man pursues for himself according to his natural
gifts and his experience in the methods of his own science, but merely
to cast some light upon the contents of the next few chapters. Logic is
here treated as a process of proof; proof supposes that some general
proposition or hypothesis has been suggested as requiring proof; and the
search for such propositions may spring from scientific curiosity or
from practical interests.

We may, as Bain observes (_Logic_: B. iii. ch. 5), desire to detect a
process of causation either (1) amidst circumstances that have