De hac attributione
The attribution of this commentary on Aristotle's De generatione et corruptione to Roger Bacon is highly probable, though not indubitable. The chief ground for doubt is its absence from Amiens 406, the single manuscript in which most of Bacon's philosophical works are preserved. Instead, it appears in Rome, Collegio Sant'Isidoro, Codex 1/10, fol. 101ra-111rb, and accordingly we will subsequently refer to this work as Isidoro. Supposing Isidoro is by Bacon, it was probably composed while Bacon was a master of arts at some point between the years 1237 and 1247.
The attribution was first suggested by the principal editor of the works preserved in Amiens 406, F. Delorme, who published them in the series Rogeri Baconi Opera hactenus inedita (henceforth OHI) together with R. Steele. Delorme based his suggestion on similarities of style and on two cross-references in Bacon's generally accepted philosophical works, one of which is a retro-reference that can be verified in Isidoro.
We repeat here and amplify somewhat the evidence Delorme adduced in his 1935 preface to Bacon's principal Physics commentary, OHI 13: xxxi. Most compelling is the retro-reference Delorme found. He noticed that Bacon first promised a commentary on De generatione et corruptione at Questiones supra undecimum prime philosophie Aristotelis (Metaphysica XII), ed. R.~Steele and F.~Delorme, Oxford 1926, OHI 7: 135. Then subsequently, Bacon cited this commentary as a completed work in Questiones supra libros octo Physicorum Aristotelis, ed. F. Delorme, Oxford 1935, OHI 13: 422. The citation in Bacon's Physics reads as follows:
[M]ateria, prout dicitur esse subjectum generationis, non sumitur pro materia pura omnino, imo sicut dictum fuit ibi, scilicet libro de Generatione, totum signatum tertii generis dicitur materia respectu naturalium rerum; corpus enim elementare quod est tertium genus dicitur materia rerum naturalium et subjectum generationis.
Delorme suggested that this reference was verified in Isidoro:
Dubitatur utrum sufficiat {sufficiam cod.} materia prima prout sub forma secunda generis ad hoc quod sit materia elementorum. ... Sicut se habet principiatum ad principiatum, sic principium ad principium; sed corpus circulare posterius est quam corpus naturale simpliciter; quare et principium corporis elementaris quam corpus simpliciter. Sed materia secundi generis est materia corporis simpliciter; ergo non erit materia corporis elementaris nisi aliquid ei addatur, et ita materia secundi generis non sufficit. Unde oportet quod sit res tertii generis, et hoc sufficit. Unde materia elementorum est substantia corporalis elementaris, et de hac loquitur hic.
Someone might object that the reference is to Aristotle, not to Bacon's commentary. However, Aristotle does not distinguish three genera of matter, and Isidoro does. Moreover, Bacon's teaching in the Physics commentary that elementary bodies constitute a third genus of matter that is the subject of generation (and corruption) is a doctrine Theodore Crowley describes as characteristic of Bacon's hylomorphism. See his Roger Bacon, Louvain 1950, p. 104. So if we encounter the same distinctive teaching in Isidoro, that further supports the attribution.
The third genus of matter is the matter of the elements. So assuming that the matter of the elements can be equated with the matter subject to generation, this is the reference Bacon intended. Why might we - and Bacon - assume that the matter subject to generation is the matter of the elements? It is generally held that not only are the elements themselves subject to generation and corruption, but also that in more complex bodies, generation just is the mixture or compounding of elements, which are destroyed or corrupted when those compounds break down. As Averroes says: "Generatio enim fit per congregationem elementorum et corruptio per segregationem eorum" (Commentarium medium in Aristotelis De generatione et corruptione 1.1, ed. F. Fobes & S. Kurland, Cambridge, MA, 1956, p. 5). Similarly, as Aquinas remarks in his preface to Generation and Corruption: "Sunt autem in genere generabilium et corruptibilium quaedam prima principia, scilicet elementa, quae sunt causa generationis et corruptionis et alterationis in omnibus aliis corporibus." What is distinctive about Bacon's teaching is the claim that we must posit a third genus of matter that is not just corporeal, but also elemental.
In some respects Isidoro is like Rufus' In Aristot. DGen (In DGen) and his In Physicam Aristot., which is why we transcribed it. It is a question commentary, copied in Incipient Anglicana and heavily influenced by Averroes. However, there are notable stylistic differences between Rufus' In Gen and Bacon's Aristotle commentaries, which are detailed in our introduction to In DGen.
Like the retro-reference from Bacon's principal Physics commentary, stylistic resemblances link Isidoro and Bacon. Isidoro, like Bacon's commentaries, generally employs a characteristic format. Bacon's commentaries introduce virtually every question with the word 'Quaeritur' or, less commonly, 'Dubitatur'; in Isidoro, 'Dubitatur' predominates, but the relentlessness of the formula is the same. A set of arguments for one side is given, with each argument usually introduced by 'Item', followed by opposing arguments, also introduced with a standard formula. Like Bacon, Isidoro frequently introduces the determination of the question with forms of the verb 'concedo' and then replies to the arguments introduced against this position with 'Ad obiectum' or 'Ad argumenta'. In contrast, the questions in other commentaries of the period are more varied in structure. It is, of course, possible for different authors to employ the same format. However, to date no other author active before 1250 or shortly thereafter is known to have repeatedly used this format, and a similar format is generally adopted in all of Bacon's Aristotle commentaries.
Isidoro also resembles Bacon's commentaries in the nature of the questions it raises. Only philosophical questions are considered. Isidoro shows no interest in questions pertaining to Aristotle's text as such, and the doubts it raises are only loosely connected to Aristotle's text.
Finally, Bacon uses quite a range of sources, with an emphasis on Avicenna, whom he considers an exceedingly faithful interpreter of Aristotle (perfectus imitator et expositor Aristotelis, Opus maius, pars quinta, ed. J. Bridges, Oxford 1897, II: 10). Even when commenting on Generation and Corruption, Isidoro finds occasion to cite Avicenna's De anima seu Sextus de naturalibus and two passages from Avicenna's Metaphysics; indeed, Avicenna is more often cited than any author except Aristotle. In addition to Avicenna, in this short work, Isidoro cites Algazel's Metaphysica, the Liber de causis, and De mirabilibus mundi.