In order to determine who the wise man was and what the intelectual activity consisted in medieval times, we will suggest a semasiological, semantical and historical study of the adjectives "cuerdo" and "entendido" in four texts of the Castilian 13th century. The objective is to determine the semantic area covered by both adjectives – etymological dictionaries do not always help us distinguish one notion from the other – and thus to find out to which extent the terminology present in these texts reflects the existence of various conceptions of knowledge, some of which therefore recently adopted.