The basic problem, as described by Paul Maas, is as follows: We have no autograph [handwritten by the original author] manuscripts of the Greek and Roman classical writers and no copies which have been collated with the originals; the manuscripts we possess derive from the originals through an unknown number of intermediate copies, and are consequently of questionable trustworthiness.
The business of textual criticism is to produce a text as close as possible to the original (constitutio textus).
The Bible and the works of William Shakespeare have often been the subjects of variorum editions, although the same techniques have been applied with less frequency to many other works, such as Walt Whitman's Leaves of Grass, Eclecticism refers to the practice of consulting a wide diversity of witnesses to a particular original.
The practice is based on the principle that the more independent transmission histories there are, the less likely they will be to reproduce the same errors.
have been applied to many works, from (near-)contemporary texts to the earliest known written documents.
Ranging from ancient Mesopotamia and Egypt to the twentieth century, textual criticism covers a period of about five millennia.
There are many approaches to textual criticism, notably eclecticism, stemmatics, and copy-text editing.
Quantitative techniques are also used to determine the relationships between witnesses to a text, with methods from evolutionary biology (Phylogenetics) appearing effective on a range of traditions.
This understanding may lead to the production of a "critical edition" containing a scholarly curated text.
Given a manuscript copy, several or many copies, but not the original document, the textual critic might seek to reconstruct the original text (the archetype or autograph) as closely as possible.