ies of our feelings which are distinguishable in
quality, and not merely in quantity or degree. The _ideal_ limit of the
explanation of natural phenomena is to show that each of these ultimate
facts has (since the differences in the different cases of it affect our
sensations as differences in degree only, and not in quality) only one
sort of cause or mode of production; and that all the seemingly
different modes of production or causes of it are resolvable into one.
But _practically_ this limit is never attained. Thus, though various
laws of Causes of Motion have been resolved into others (e.g. the fall
of bodies to the earth, and the motions of the planets, into the one law
of mutual attraction), many causes of it remain still unresolved and
distinct.

Hypotheses are made for the sake of this resolving and explaining of
laws. When we do not _know_ of any more general laws into which to
resolve an uniformity, we then (either on no or on insufficient
evidence) _suppose_ some, imagining either causes (as, e.g. Descartes
did the Vortices), or the laws of their operation (as did Newton
respecting the planetary central force); but we never feign both cause
and law. The use of a hypothesis is to enable us to apply the Deductive
Method before the laws of the causes have been ascertained by Induction.
In those cases where a false law could not have led to a true result (as
was the case with Newton's hypothesis as to the law of the Attractive
force) the third part of the process in the Deductive Method, viz.
Verification, which shows that the results deduced are true, amounts to
a complete induction, and one conforming to the canon of the Method of
Difference. But this is the case only when either the cause is known to
be one given agent (and only its law is unknown), or to be one of
several given agents.

An assumed cause, on the other hand, cannot be accepted as true simply
_because_ it explains the phenomena (since two conflicting hypotheses
often do this even originally, or, as Dr. Whewell himself allows, may at
any rate by modifications be made to do it); nor _because_ it moreover
leads to the prediction of other results which turn out true (since this
shows only what was indeed apparent already from its agreement with the
old facts, viz. that the phenomena are governed by laws partially
identical with the laws of other causes); nor _because_ we cannot
imagine any other hypothesis which will account for the facts (since