day for months at a certain place at a certain hour, it
is reasonable to expect to meet him there to-morrow, even if
our knowledge does not go beyond the observed facts of repeated
coincidence. But if we know also what brings him there, and that this
cause continues, we have a stronger reason for our expectation. And so
with the case of poles at regular intervals on a road. If we know why
they are placed there, and the range of the purpose, we expect their
recurrence more confidently within the limits of that purpose. This
further knowledge is a warrant for stronger confidence, because if
we know the producing causes, we are in a better position for knowing
whether anything is likely to defeat the coincidence. A uniformity is
said to be explained when its cause is known, and an inference from an
explained uniformity is always more certain than an inference from
a uniformity that is merely empirical in the sense of being simply
observed.

Now, the special work of Science is to explain, in the sense of
discovering the causes at work beneath what lies open to observation.
In so doing it follows a certain method, and obeys certain conditions
of satisfactory explanation. Its explanations are inferences from
facts, inasmuch as it is conformity with observed facts, with outward
signs of underlying causal nexus, that is the justification of them.
But they are not inferences from facts in the sense above described
as empirical inference. In its explanations also Science postulates
a principle that may be called the Uniformity of Nature. But this
principle is not merely that observed uniformities continue. It may
be expressed rather as an assumption that the underlying causes
are uniform in their operation, that as they have acted beneath the
recorded experiences of mankind, so they have acted before and will
continue to act.

The foregoing considerations indicate a plan for a roughly systematic
arrangement of the methods of Induction. Seeing that all inference
from the data of experience presupposes causal connexion among the
data from which we infer, all efforts at establishing sound bases of
inference, or rational ground for expectation fall, broadly speaking,
under two heads: (1) Methods of ascertaining causal connexion among
phenomena as a matter of fact, that is, Methods of Observation; and
(2) Methods of ascertaining what the causal connexion is, that is,
Methods of Explanation.

These constitute the body of Inducti