ea of its scope you may waste time through not knowing your
way and so following false leads.

In your reading do not rest satisfied with consulting authorities on
your own side only. We shall presently see how important it is to be
prepared to meet arguments on the other side; and unless you have read
something on that side, you will not know what points you ought to deal
with in your refutation. In that event you may leave undisturbed in the
minds of your readers points which have all the more significance from
your having ignored them. One of the first reasons for wide reading in
preparation for an argument is to assure yourself that you have a
competent knowledge of the other side as well as of your own.

In using your sources keep clearly and constantly in mind the difference
between fact and opinion. The opinions of a great scholar and of a
farseeing statesman may be based on fact; but not being fact they
contain some element of inference, which is never as certain. When we
come to the next chapter we shall consider this difference more closely.
In the meantime it is worth while to urge the importance of cultivating
scruples on the subject and a keen eye for the intrusion of human, and
therefore fallible, opinion into statements of fact. A trustworthy
author states the facts as facts, with the authorities for them
specifically cited; and where he builds his own opinions on the facts he
leaves no doubt as to where fact ends and opinion begins.

The power to estimate a book or an article on a cursory inspection is of
great practical value. The table of contents in a book, and sometimes
the index, will give a good idea of its scope; and samples of a few
pages at a time, especially on critical points, which can be chosen by
means of the index, will show its general attitude and tone. The index,
if properly made, will furnish a sure guide to its relevance for the
purpose in hand. Half an hour spent in this way, with attention
concentrated, will in most cases settle whether the book is worth
reading through. An article can be "sized up" in much the same way:
if it is at all well written the first paragraphs will give a pretty
definite idea of the subject and the scope of the article; and the
beginnings, and often the ends, of the paragraphs will show the course
which the thought follows. Though such skimming cannot be relied on for
a real knowledge of the subject, it is invaluable as a guide for this
preliminary readi