Thursday, 17 September 2009

Fractio Aeris: A Cracking Tale of Two Villains

In his excellent book Theology at Paris (2000), Chris Schabel reports Michael of Massa (fl. c.1330–37) as having suggested that God could form a declarative sentence about the future "by the cracking of the sky".  This is a rather melodramatic translation; the Latin phrase ‘per aeris fractionem’ need only mean "by the cracking of air".  But the history of this phrase is the history of a more serious mistranslation.

In De anima II.8, Aristotle says that sound is the result of the collision of solid objects with each other and with the air (or other medium), which "happens when the air remains after being struck and is not dispersed; wherefore it makes a sound if it is struck quickly and violently, for the movement of the striker must come sooner than (φθασαι) the dispersal of the air".  He gives an analogy with a heap of sand: you must hit it quickly, or it will just part around your hand.

The first villain of the piece is James of Venice (fl. c.1125–50), who translated the last clause as  "Oportet enim pertingere motum rapientis fracturam aeris"  (for the movement of the violent snatcher must attain the breaking of the air), thus turning what the speed of the blow was meant to avoid into what it was meant to achieve.

Still, two commentaries from the mid-to-late 1240s gave generous glosses:  "pertingere, id est antecedere" (ed. Bazan 1998);  "pertingere, id est excedere, fracturam aeris, id est: oportet quod velocior sit motus percutientis quam possit esse [fracturam aeris] percussi" (ed. Gauthier 1985).  Even better, in 1267 William of Moerbeke corrected ‘pertingere’ to ‘preoccupare’ (anticipate), and Aquinas presented an accurate account in his De anima commentary the following year:  "oportet quod motus percutientis praeveniat divisionem aeris". 

Enter the second villain of the piece: the influential florilegium Parvi flores or Auctoritates Aristotelis (c.1297–98), which paraphrases the De anima passage as saying that sound is caused by the collision of bodies aerem violenter frangentium (violently breaking the air).

In 1316, Auriol discusses Balaam's talking ass as a challenge to his claim that any form impressible on matter can be impressed on it by a natural agent (S I.42.1.iii.3).  He points out that "similem sonum et fractionem aeris potest causare aliquod agens naturale" (a similar sound and breaking of the air can be caused by a natural agent); what is unnatural is just  "motionem ipsius linguae brutalis ex qua sequitur fractio aeris et sonus in aere" (the motion of the beastly tongue itself from which there follows the breaking of the air and the sound in the air).  This passage is surely sufficient to explain the Massa quotation.

My final exhibit is from the introduction to Jean de Meurs’ Musica speculativa secundum Boetium (1323):  "Ad generationem soni tria necessario requiruntur, scilicet percutiens, percussum et medium percutiendi.  Primum frangens aerem celeriter, secundum corpus sonabile naturaliter, tertium aer fractus violenter. … Est igitur sonus fractio aeris ab impulsu percutientis ad percussum."

This is a patchy story, but I think it will hold water.  Anyone wishing to flesh it out should no doubt seek out (as I have not) Wittmann, Vox atque sonus: Studien zur Rezeption der Aristotelischen Schrift "De anima" und ihre Bedeutung für die Musiktheorie, 2 vols (1987).