How do scholars identify the archetype of a manuscript tradition?

In the context of textual criticism, scholars identify the archetype—the lost manuscript from which surviving copies descend—primarily through the "genealogical" or "stemmatic" method.

This process involves the following steps:

• Collation: Scholars identify, date, and describe all extant witnesses (copies, editions, or citations) and compare their variant readings against a standard text.1
• Stemma Construction: By analyzing shared variants, particularly errors and omissions, critics map the relationships between witnesses to create a family tree known as a stemma codicum.1
• Reconstruction: Witnesses that merely repeat the testimony of others are discarded. The archetype is then reconstructed by comparing the agreements of the remaining independent branches of the family tree.1

This method assumes "vertical" transmission, where a copyist follows a single model. If a manuscript incorporates variants from multiple sources—a process called "horizontal" or "contaminated" transmission—constructing a stemma becomes significantly more complex or even impossible.1

Note: The term "archetype" in this technical sense should not be confused with the concept of a "primordial image" used in literary criticism and Jungian psychology.2