l. It is useful, when it attracts attention to topics
which might otherwise be neglected; and when, as does sometimes
happen, those who come to see a contest remain to think. It is
necessary, when the interests of truth and of justice are at stake.
It is an evil, in so far as controversy always tends to degenerate
into quarrelling, to swerve from the great issue of what is right and
what is wrong to the very small question of who is right and who is
wrong. I venture to hope that the useful and the necessary were more
conspicuous than the evil attributes of literary militancy, when these
papers were first published; but I have had some hesitation about
reprinting them. If I may judge by my own taste, few literary dishes
are less appetising than cold controversy; moreover, there is an air
of unfairness about the presentation of only one side of a discussion,
and a flavour of unkindness in the reproduction of "winged words,"
which, however appropriate at the time of their utterance, would find
a still more appropriate place in oblivion. Yet, since I could hardly
ask those who have honoured me by their polemical attentions to confer
lustre on this collection, by permitting me to present their
lucubrations along with my own; and since it would be a manifest wrong
to them to deprive their, by no means rare, vivacities of language of
such justification as they may derive from similar freedoms on my
part; I came to the conclusion that my best course was to leave the
essays just as they were written;[8] assuring my honourable
adversaries that any heat of which signs may remain was generated, in
accordance with the law of the conservation of energy, by the force of
their own blows, and has long since been dissipated into space.

But, however the polemical coincomitants of these discussions may be
regarded--or better, disregarded--there is no doubt either about the
importance of the topics of which they treat, or as to the public
interest in the "Controverted Questions" with which they deal. Or
rather, the Controverted Question; for disconnected as these pieces
may, perhaps, appear to be, they are, in fact, concerned only with
different aspects of a single problem, with which thinking men have
been occupied, ever since they began seriously to consider the
wonderful frame of things in which their lives are set, and to seek
for trustworthy guidance among its intricacies.

Experience speedily taught them that the shifting scenes of