Isidore wished to present a complete education in all branches of learning to his intended audience as is shown by his wide and varied writings, above all the Etymologiae. Grammar formed the indispensable foundation of this education as a sound understanding of language was the only path, as he saw it, to any further area of study. Above all, therefore, Isidore wrote as a grammaticus and presents in the first book of the Etymologiae a detailed resumen of necessary grammatical learning. This programme is linked to the tradition associated with Aelius Donatus which had become the principle model for schools in Late Antiquity and the High Middle Ages. To it were added other elements which were of especial concern to schools in Visigothic Iberia: orthography, metre, and, above all, the acquisition of a large vocabulary. This particular focus on commanding a knowledge of a wide variety of words and their precise meanings is what led Isidore to pay special attention to lexical differences, synonyms and etymology and writing specific works focussed on these topics. As a result, his Differentiae, Synonyma, and Etymologiae, while having dogmatic, technical or academic content, are also thesauri of vocabulary, guides to writing, and, therefore, works of grammar. It is thanks to these works that Isidore came to be regard as the master of grammar in the centuries following his death and that his works frequently circulated in medieval codices as parts of compilications dealing with grammar.