 Avempace inserted his classification of the sciences into the Eisagoge, a treatise whose aim is to discover the simple universal categories underlying the parts of the sentences. His master Alfarabi added the chapters on definition, borrowed from the Aristotelian Analytica Posteriora. Alfarabi had also introduced, at the beginning and in his enumeration of the parts of the sentence, the distinction between “sound” (lafẓ) and “meaning” (ma‛nà) and said: