it was essentially the art of preventing
and exposing quibbling. It had its origin in quibbling, no doubt,
inasmuch as what we should call verbal quibbling was of the essence
of Yes-and-No Dialectic, and the main secret of its charm for an
intellectual and disputatious people; but it came into being as a
safeguard against quibbling, not a serviceable adjunct.

The mediaeval developments of Logic retained and even exaggerated
the syllogistic character of the original treatises. Interrogative
dialectic had disappeared in the Middle Ages whether as a diversion or
as a discipline: but errors of inconsistency still remained the errors
against which principally educated men needed a safeguard. Men had
to keep their utterances in harmony with the dogmas of the Church. A
clear hold of the exact implications of a proposition, whether singly
or in combination with other propositions, was still an important
practical need. The Inductive Syllogism was not required, and its
treatment dwindled to insignificance in mediaeval text-books, but the
Deductive Syllogism and the formal apparatus for the definition of
terms held the field.

It was when observation of Nature and its laws became a paramount
pursuit that the defects of Syllogistic Logic began to be felt. Errors
against which this Logic offered no protection then called for a
safeguard--especially the errors to which men are liable in the
investigation of cause and effect. "Bring your thoughts into harmony
one with another," was the demand of Aristotle's age. "Bring your
thoughts into harmony with authority," was the demand of the Middle
Ages. "Bring them into harmony with fact," was the requirement most
keenly felt in more recent times. It is in response to this demand
that what is commonly but not very happily known as Inductive Logic
has been formulated.

In obedience to custom, I shall follow the now ordinary division of
Logic into Deductive and Inductive. The titles are misleading in many
ways, but they are fixed by a weight of usage which it would be vain
to try to unsettle. Both come charging down the stream of time
each with its cohort of doctrines behind it, borne forward with
irresistible momentum.

The best way of preventing confusion now is to retain the established
titles, recognise that the doctrines behind each have a radically
different aim or end, and supply the interpretation of this end from
history. What they have in common may be described as the preve