Liber de causis

The Liber de causis ("Book of Causes") is a philosophical work composed in Arabic in the 9th century. It was once attributed to Aristotle and became popular in West during the Middle Ages, after it was translated into Latin by Gerard of Cremona between 1167 and 1187.^[1] The original title was كتاب الإيضاح لأرسطوطاليس في الخير المحض Kitāb al-Īḍāḥ li-Arisṭūṭālis fī l-Khayr al-Maḥd, "The Book of Aristotle's Explanation of the Pure Good".^[2] Its Latin title, Liber de causis, came into use following its translation. The work was also translated into Armenian and Hebrew.^[3] Many Latin commentaries on the work are extant.^[4] Albertus Magnus attributed the Liber de causis to a certain David, a Jew, who in some sources appears as the author under the name of Avendauth, i.e. Ibn David.^[5]

Manuscript copy of the Liber de causis from c. 1470. This copy once belonged to Cardinal Bessarion and is now in the Biblioteca Nazionale Marciana in Venice.

Leiden manuscript of al-Īḍāḥ fī'l-Khayr al-Maḥḍ, Or. 209.

The real authorship of the Liber remains a mystery, but most of the content is taken from the Elements of Theology of the Neoplatonic philosopher Proclus. This was first noticed by Thomas Aquinas,^[6] following William of Moerbeke's translation of Proclus' work into Latin.^{[citation needed]} As such its author is now known as pseudo-Aristotle.^[7]