Concordance

A concordance is an exhaustive index of a text. For every substantive word, it lists every place that word appears, usually with a short window of surrounding text and a citation. The classical model is Alexander Cruden's Complete Concordance to the Holy Scriptures (1737), a single-handed labour of nearly a decade that let generations of preachers find any verse from any half-remembered phrase.

Concordances were originally biblical tools, produced for the Vulgate in the thirteenth century and for the English Bible in the sixteenth. They spread from there to Shakespeare, Milton, and later to any author whose reception justified the enormous labour of manual compilation. In the digital era, most of that labour has moved to search interfaces, but the underlying idea — every word, every occurrence, in context — is unchanged.

For quotation work, a concordance is the tool that verifies attribution. If a phrase is claimed to appear in Shakespeare, the concordance settles the question in a minute; if it does not appear, the misattribution can be pinned down and the actual source, if any, hunted elsewhere. Modern quote-investigation depends on the same principle applied at internet scale.

Common mistake: confusing a concordance with an index. An index points to topics discussed; a concordance points to words used. A book on liberty may not contain the word 'liberty' on every page it indexes under that head, and a concordance will not always agree with an index about where the important passages are.