The death of Beatrice, on June 8, 1290, was succeeded, for Dante, by a period of intense study: for about 30 months (as he said in the Convivio) he attended "the schools of the religious and the disputations of the philosophers" and in deep study prepared the ground for the great works of his maturity. He became acquainted with such classical authors as Virgil, Ovid, Lucan, and Statius. Through his reading of St. Thomas Aquinas' commentary he came to know the works of Aristotle, especially Ethics and Politics; and he read medieval authors such as Albertus Magnus, St. Bonaventure, and Averroes. These studies gave a new dimension to his poetry, extending its limits beyond the themes of love, as is reflected in the allegorical canzoni in praise of philosophy and his doctrinal verses. To the same period belong four rime petrose (December 1296) written for Pietra, a lady who had rashly rejected his love; they too give evidence of mature experiment in metre and style. The philosophical canzoni, with their judgment of current ideas and modes of life, are the fruit of meditation on daily experience of the class prejudices that underlay the violence of the magnates, a theme that was to recur in the eighth canto of the Inferno with the episode of Filippo Argenti. Dante already adhered firmly to the democratic ideals of the Guelf commune.