 He is son to Manuel Alvar, a prominent Spanish philologist.Alvar's research has been almost totally concentrated on the Spanish Modern Age; in his first years, the kingdom of Philip II and how Madrid became the permanent headquarters of the Court drew his attention; afterwards, his fields of research have comprised, to name a few, historiography, arbitrismo (judgments proposed to solve problems of the kingdom, mainly regarding the dire situation of the royal treasury; it can be considered one of the first economic literature of the Modern Age) and biographies of relevant people in the Spanish 16th and 17th centuries.Anthony Giddens’ theory of structuration and the Annales School and Fernand Braudel, have been extremely influential in Alvar's thinking, and sociology and economy are present throughout his works.