The title of Doctor, or as he said himself, "Maestro delle Arti," which Bruno had obtained at Toulouse, gave him the faculty of teaching publicly in Paris, and he says: "I went to Paris, where I set myself to read a most unusual lecture, in order to make myself known and to attract attention." He gave thirty lectures on the thirty Divine attributes, dividing and distributing them according to the method of St. Thomas Aquinas: these lectures excited much attention amongst the scholars of the Sorbonne, who went in crowds to hear him; and he introduced, as usual, his own ideas while apparently teaching the doctrines of St. Thomas. His extraordinary memory and his eloquence caused great astonishment; and the fame of Bruno reached the ears of King Henry III., who sent for him to the Court, and being filled with admiration of his learning, he offered him a substantial subsidy.
During his stay at Paris, although he was much at Court, he spent many hours in his study, writing the works that he afterwards published.
Philosophical questions were discussed at the Sorbonne with much freedom: Bruno showed himself no partisan of either the Platonic or the Peripatetic
school; he was not exclusive either in philosophy or in religion; he did not favour the Huguenot faction more than the Catholic league; and precisely by reason of this independent attitude, which kept him free of the shackles of the sects, did he obtain the faculty of lecturing at the Sorbonne. Nor can we ascribe this aloofness to religious indifference, but to the fact that he sought for higher things and longed for nobler ones. The humiliating spectacle which the positive religions, both Catholic and Reformed, presented at that time—the hatreds, the civil wars, the assassinations which they instigated—had disgusted men of noble mould, and had turned them against these so-called religions; so that in Naples, in Tuscany, in Venice, in Switzerland, France, and England, there were to be found societies of philosophers, of free-thinkers, and politicians, who repudiated every positive religion and professed a pure Theism.
In the "Spaccio della Bestia Trionfante" he declares that he cannot ally himself either to the Catholic or the Lutheran Church, because he professes a more pure and complete faith than these—to wit, the love of humanity and the love of wisdom; and Mocenigo, the disciple who ultimately betrayed and sold him to the Holy Office, declares in his deposition that Bruno sought to make himself the
author of a new religion under the name of "Philosophy." He was not a man to conceal his ideas, and in the fervour of his improvisation he no doubt revealed what he was; some tumult resulted from this free speaking of Bruno's, and he was forced to discontinue his lectures at the Sorbonne.
Towards the end of the year 1583 the King became enthralled by religious enthusiasm, and nothing was talked of in Paris but the conversion of King Henry. This fact changed the aspect of affairs as far as Bruno was concerned; he judged it prudent to leave Paris, and he travelled to England.
The principal works published by Bruno during his stay in Paris are "Il Candelajo" and "Umbrae Idearum." The former, says Levi, is a work of criticism and of demolition; in this comedy he sets in groups the principal types of hypocrisy, stupidity, and rascality, and exhibiting them in their true colours, he lashes them with ridicule. In the "Umbrae Idearum" he initiates the work of reconstruction, giving colour to his thought and sketching his idea. The philosophy of Bruno is based upon that of Pythagoras, whose system penetrates the social and intellectual history of Italy, both ancient and modern. The method of Pythagoras is not confined, as most philosophies are, to pure metaphysical
speculations, but connects these with scientific observations and social practice. Bruno having resuscitated these doctrines, stamps them with a wider scope, giving them a more positive direction; and he may with propriety be called the second Pythagoras. The primal idea of Pythagoras, which Bruno worked out to a more distinct development is this: numbers are the beginning of things; in other words numbers are the cause of the existence of material things; they are not final, but are always changing position and attributes; they are variable and relative. Beyond and above this mutability there must be the Immutable, the All, the One.
The Infinite must be one, as one is the absolute number; in the original One is contained all the numbers; in the One is contained all the elements of the Universe.