Lectio difficilior potior

Lectio difficilior potior (Latin: "the difficult reading is stronger") is an important, internal criterion in textual criticism. When different manuscripts of a text conflict, this principle requires that the harder, unusual, more obtuse reading is to be preferred. It is based on the assumption that scribes are more likely to replace odd words in difficult places with more familiar vocabulary in more expected positions.

It was one principle among many that became established in early 18th-century textual criticism, being part of an attempt by scholars of the Age of Enlightenment to provide a neutral basis for discovering an urtext that was independent of the weight of traditional authority.