A facsimile has been defined as “a reproduction which copies the original…as accurately as is possible within the limits of the reproductive process employed”. The expression can of course be applied to illustrations as well, but this aspect has already been treated in the previous chapter. We are here concerned only with reproductions of books as a whole, text-matter or MS. Weitenkampf says that “every facsimile is a copy, but not every copy is a facsimile”, and further that “before 1870, the use of the word had no justification whatever”. Contrast a saying by another prominent bibliographer, that “photographic reproductions [are] reliable but illegible, reprints are legible but unreliable”.

The user of facsimiles must make his choice according to his requirements. The word “facsimile” was known and used long before 1870; apart from the reproduction of pictures they were used as precepts when the interest in handwriting awakened. Today they are used widely by scholars for critical editions, where every existing copy of an early, rare book should be examined; for research purposes when inaccessible materials are wanted; for literary students who may be satisfied with a reprint in one form or another; by scientists for articles in periodicals; by the general public for whom early editions have an aesthetic appeal; and lastly, by those individuals who fabricate old and rare editions, of whom more later.

The categories fall into the three well-known groups: relief, intaglio, and planographic, each again within the two groups: non-photographic, and photographic.