Dante Alighieri

De monarchia
The Latin treatise De monarchia, in three books, contains the mature statement of Dante's political ideas. In it he propounds the theory that the supremacy of the emperor is derived from the supremacy of the Roman people over the world, which was given to them direct from God. As the emperor is intended to assure their earthly happiness, so does their spiritual welfare depend upon the pope, to whom the emperor is to do honour as to the first-born of the Father. The date of its publication is almost universally admitted to be the time of the descent of Henry VII. into Italy, between 1310 and 1313, although its composition may have been in hand from a much earlier period. The book was first printed by Oporinus at Basel in 1559, and placed on the Index of forbidden books.

De vulgari eloquentia
The treatise De vulgari eloquentia, in two books, also in Latin, is mentioned in the Convito. Its object was first to establish the Italian language as a literary tongue, and to distinguish the noble or "courtly" speech which might become the property of the whole nation, at once a bond of internal unity and a line of demarcation against external nations, from the local dialects peculiar to different districts; and secondly, to lay down rules for poetical composition in the language so established. The work was intended to be in four books, but only two are extant. The first of these deals with the language, the second with the style and with the composition of the canzone. The third was probably intended to continue this subject, and the fourth was destined to the laws of the ballata and sonetto. It contains much acute criticism of poetry and poetic diction. This work was first published in the Italian translation of Trissino at Vicenza in 1529. The original Latin was not published till 1577 at Paris by Jacopo Corbinelli, one of the Italians who were brought from Florence by Catherine de' Medici, from a MS. now preserved at Grenoble. The work was probably left unfinished in consequence of Dante's death.