ersy, but because the opportunity was favourable for
placing my own conclusions, and the grounds of them, more clearly and
completely before the reader. Truth, on these subjects, is militant, and
can only establish itself by means of conflict. The most opposite opinions
can make a plausible show of evidence while each has the statement of its
own case; and it is only possible to ascertain which of them is in the
right, after hearing and comparing what each can say against the other,
and what the other can urge in its defence.

Even the criticisms from which I most dissent have been of great service
to me, by showing in what places the exposition most needed to be
improved, or the arguments strengthened. And I should have been well
pleased if the book had undergone a much greater amount of attack; as in
that case I should probably have been enabled to improve it still more
than I believe I have now done.

INTRODUCTION.