ion, into the laws which connect each link with the intermediate
links; or--3. By the _subsumption_ or gathering up of several laws under
one which amounts to the sum of them all, and which is the recognition
of the same sequence in different sets of instances. In the first two of
the processes, laws are resolved into others, which both extend to more
cases, i.e. are more _general_, and also, as being laws of nature, of
which the complex laws are but results, are more _certain_, i.e. more
_unconditional_ and more _universally true_. In the third process, laws
are resolved into others which are indeed more _general_, but not more
_certain_, since they are in fact the same laws, and therefore, subject
to the same exceptions.

Liebig's researches, e.g. into the Contagious Influence of Chemical
Action, and his Theory of Respiration, are among the finest examples,
since Newton's exposition of the law of gravitation, of the use of the
deductive method for _explanation_.[2] But the method is as available
for explaining mental as physical facts. It is destined to predominate
in philosophy. Before Bacon's time deductions were accepted as
sufficient, when neither had the premisses been established by proper
canons of experimental enquiry, nor the results tested by verification
by specific experience. He therefore changed the method of the sciences
from deductive to experimental. But, now that the principles of
deduction are better understood, it is rapidly reverting from
experimental to deductive. Only it must not be supposed that the
inductive part of the process is yet complete. Probably, few of the
great generalisations fitted to be the premisses for future deductions
will be found among truths now known. Some, doubtless, are yet unthought
of; others known only as laws of some limited class of facts, as
electricity once was. They will probably appear first in the shape of
hypotheses, needing to be tested by canons of legitimate induction.

FOOTNOTE:

[2] These, and other illustrations in chap. xiii., cannot be usefully
represented in an abridged form.

CHAPTER XIV.

THE LIMITS TO THE EXPLANATION OF LAWS OF NATURE. HYPOTHESES.

The constant tendency of science, operating by the Deductive Method, is
to resolve all laws, even those which once seemed ultimate and not
derivative, into others still more general. But no process of
_resolving_ will ever reduce the number of ultimate laws below the
number of those variet