Auraicept na n-Éces

The text is the first instance of a defence of a western European vernacular, defending the spoken Irish language over Latin, predating Dante's De vulgari eloquentia by several hundred years.

The Auraicept consists of four books, The author argues from a comparison of Gaelic grammar with the materials used in the constructions of the Tower of Babel: Others affirm that in the tower there were only nine materials and that these were clay and water, wool and blood, wood and lime, pitch, linen, and bitumen ...

Calder notes (p. xxxii) that the poetic list of the "72 races" was taken from a poem by Luccreth moccu Chiara.

The Auraicept is one of the three main sources of the manuscript tradition about Ogham, the others being In Lebor Ogaim and De dúilib feda na forfed.

Similar to the argument of the precedence of the Gaelic language, the Auraicept claims that Fenius Farsaidh discovered four alphabets, the Hebrew, Greek and Latin ones, and finally the ogham, and that the ogham is the most perfected because it was discovered last.