SIGER OF BRABANT. - Belgian philosopher, perhaps a disciple of Albert the Great, a contemporary of St. Thomas, whose adversary he was in the interpretation of Aristotle's thought. Few details are known about his life. He is first found involved in the university disturbances of 1266 in Paris, as a master in the Faculty of Arts, a member of the Picard "nation" and accused of having resorted to violence.
Around 1270 he must have been the best known of a small group of masters who, because they held that Aristotle was to be understood in the manner of Averroes, called themselves Averroists (v. AVERROISMO). The thirteen cardinal points of this Aristotelian Averroism were the object of a first condemnation pronounced on 10 Dec. 1270 by the bishop of Paris (Chartul. Univers. Paris., I, pp. 486-87). From the same year, and perhaps earlier than this condemnation, appears to date Thomas's Tractatus de unitate intellectus contra averroistas, which in the Munich codex lat. 8001, from the beginning of the 14th century, is directed in particular contra magistrum Sagerum, and in the Oxford codex, A. 3. 12, likewise from the beginning of the 14th century, contra magistrum Sigerum de Barbantia et alios plurimos Parisius regentes anno Domini M. CC. 70.
The conflict between S. and Thomas takes shape in these terms: for the latter, Aristotle's thought agrees perfectly with Christian thought, on condition that it be freed from the interpretation of Averroes, "qui non tam fuit peripateticus quam peripateticus philosophiae depravator" (St. Thomas, De unit. intell., II, 59); for S., on the other hand, Averroes understood Aristotle well, whose thought on many fundamental articles in no way agrees with the faith. Sigierian Averroism thus rendered impossible the concordist aim that the Aquinate had proposed to himself. The latter insinuated the suspicion that the Averroists, while entrenching themselves behind their interpretation of Aristotle, secretly, "in angulis", professed the doctrines they attributed to the Greek philosopher. In a meeting of masters convoked in Paris on 1 Apr. 1272, in the church of St. Genevieve, it was resolved, among other things: "Quod si magister vel bachellarius aliquis nostre facultatis passus aliquos difficiles vel aliquas questiones legat vel disputet, que fidem videantur dissolvere, aliquatenus videatur; rationes autem seu textum, si que contra fidem, dissolvat, vel etiam falsas simpliciter et erroneas totaliter esse concedat, et aliter huiusmodi difficultates vel in textu vel in suctoritibus disputare vel legere non presumat, sed hec totaliter tanquam erronea pretermittat" (Chartul. Univers. Paris., I, p. 409). This grave and inopportune statute placed in great embarrassment the masters and bachelors who had to expound Aristotle, and who found themselves compelled, when they came upon texts or raised hermeneutical problems "que fidem videantur dissolvere", either to engage in polemic against Aristotle and declare certain of his doctrines "simply false and wholly erroneous", or to pass over them in silence. Nevertheless S. and his bachelors conformed to the decree, declaring, whenever they found themselves having to discuss heterodox theses, that those theses were necessary according to Aristotle's philosophy, but "simply false" according to the faith; for the rest they did nothing to refute them, since their task was that of interpreters of Aristotelian thought, and they did not even resign themselves to keeping silent. Hence perhaps the grave split in the Faculty of Arts, between the "para Sigerii" (Chartal., cit., I, pp. 523 and 527) and his adversaries, to settle which the papal legate Simon de Brion had to intervene, with his sentence of 7 May 1273, in which many abuses are denounced, but, to tell the truth, no mention is made of heretical doctrines.
The accusation of heresy against S. and some of his companions was not long in being whispered, however, and in the course of 1276 he cautiously hastened to return to his homeland. But the inquisitor of France, Simon du Val, reached him at Liège, with a formal citation dated 23 Oct. 1276, in which were cited to appear before him, at St. Quentin, "Suggerum de Brabancio canonicum sancti Pauli Leodiensis, et magistrum Gossioynum de Capella canonicum sancti Martini Leodiensis, et magistrum Bernerum de Wuulla [l. Nivella] canonicum eiusdem, de crimine heresis probabiliter et vehementer suspectos" (cod. Vat. lat. 3978, f. 82ᵃ-83ᵃ, pointed out by Fr. Dondaine). The deadline for appearance was fixed for the Sunday after the octave of the Epiphany 1277.
But meanwhile Pope John XXI in a letter to the bishop of Paris, of 18 Jan. 1277, declared himself worried by the swarming in that University of errors prejudicial to the faith; and the papal intervention hastened the condemnation, on the part of the bishop and the academic authorities, of 7 March 1277, in which, together with many Averroistic or otherwise heretical propositions, even some theses of St. Thomas are struck.
It does not seem plausible that, after 1276, S. returned to teaching in Paris. From a notice gathered by the continuator of the chronicle of Martin of Poland (MGH, Script., XXIV, p. 263) we learn that, "o quod quadam opiniones contra fidem tenuerat, Parisius subsistere non valens, Romanam curiam adit ibique post parvum tempus a clerico suo quasi dementi perfossus perit". This appears to have happened "nella corte di Roma ad Orbiviero", according to Il fiore, XCII, 9-11, before Nov. 1284, under the pontificate of Martin IV, who was none other than the pontifical legate in France Simon de Brion.
For the recovery of S.'s writings, and for the list of these, one must consult the great monograph of Fr. P. Mandonnet, who undertook their publication, and the more recent work of F. van Steenberghen. However, while the former laid it on thick about S., more than befits an unprejudiced historian, the latter has presented a portrait of the Belgian Averroist which, being founded on the attribution to him of writings that certainly do not belong to him, never corresponds to the truth. Mandonnet saw in S. the shifty heretic who denies as a philosopher what he affirms as a believer. Van Steenberghen, on the other hand, presents an S. who, an Averroist at the outset, gradually softens his original Averroism, and in the end (when?) winds up converting, at least in the principal theses, to Thomism.
It is certain that S. at first, that is, before 10 Dec. 1270, denied with Averroes that for Aristotle the single and separate possible intellect can be called the form of the human body, so that the proposition "this man understands" is not true; what understands is the intellect, not the man (Giles of Rome, In II Sent., dist. 17, q. 2, a. 1; John of Baconthorpe, Quodlib., I, q. 1, a. 1). But "postquam vidit decretalem", that is, the decree of condemnation of 10 Dec. 1270, this "venerable doctor" revised his position, seeking to reconcile his interpretation of Aristotle with the episcopal decree (John of Baconthorpe, loc. cit.). As a document of this effort of his there could serve the Quaestiones super 3ᵃⁿˢ de anima, of Merton College, Oxford, cod. 292 (unpublished), where (q. 1) the rational soul is a composite substance or form, resulting from the intimate union of the intellect (single and separate) with the the vegetative-sensitive part. Even the Quaestiones de anima intellectiva, edited by Mandonnet, admit that the intellective soul can be called the form of man insofar as it is «operans intrinsecus et appropriatus ad corpus» (qq. 3 and 7). S. seems to have taken a further step forward with the Tractatus de intellectu, now lost, but which was still being read at Padua at the end of the 15th century. In this work, written in reply to the Tractatus de unitate intellectus of St. Thomas, S. returned to the concept of the human soul as a composite form of the intellect (unique) and of the cogitative power (individual), and admitted that such a composite form can be called substantial, inherent in the human body and «dans esse homini». This does not at all mean an evolution toward Thomism, but an internal deepening of Averroism.
Thomas of Wilton, Paul of Venice (v.), G. Pico della Mirandola (v.), A. Achillini, T. Bacilieri, for some time A. Nifo (v.) and Pomponazzi (v.), G. Taiapietra and Antonio Bernardi della Mirandola looked favorably on such a doctrine.
For the rest, the other doctrines of S. are those mentioned in the entry AVERROISMO. He seems to have given particular emphasis, in a book De felicitate, likewise lost, to man's knowledge of separate substances and to the Averroistic theory of the copulatio of the possible intellect with the agent intellect identified with God.
"Magistrum magnum, in philosophia maiorem qui tunc esset Parisius," says Giles of Rome (loc. cit.), who knew him while he was a bachelor. "Sygerus magnus" is also what he is called in cod. lat. 16,222 of the Bibliothèque nationale in Paris (f. 74ᵃ). Dante places him in the heaven of the sun among the great sages who illuminated the Christian world with their light, beside Thomas, who delivers a moving eulogy of him who had once been his adversary on earth (Par., X, 133-38).