The Elements of Avicenna's Physics by Andreas Lammer

Author:Andreas Lammer
Language: eng
Format: epub
Publisher: De Gruyter
Published: 2018-01-15T00:00:00+00:00

If the removal of that part of it is not possible unless (aw)1325 there is an expansion [such that] the remaining rest becomes its original volume,1326 because of the impossibility of the occurrence of the void and the necessity that [everything] is filled – and this expansion is possible – and if the agent acting by force has the power required for bringing this possibility into actuality through his attraction of it to one side, while its surface adheres (luzūm saṭḥihī) to what is adjacent to its [other] side … then part of what expanded will reach1327 the outside of the phial – and this is what has been sucked out – and the rest will necessarily1328 remain filling the phial, having been expanded due to the necessity of the sucking attraction through the length of the phial. (al-Samāʿ al-ṭabīʿī II.9, §20, 146.6–11, tr. by McGinnis, modified)1329

According to Avicenna’s understanding, what happens inside the phial is that the air is forcefully, i.e., unnaturally, enlarged. Throughout the process, the air does nothing but strive for retaining its natural volume inside the phial and to stick to its place – and its place is the inner surface of the containing body (in this case the phial) which is in contact with the outer surface of the contained body (in this case the air). The reason it is difficult and exhausting to suck the air out of the phial is the same reason it is difficult and exhausting to lift a heavy stone: doing this means to counter-act the nature of a natural body and to perceive its inclination (mayl) first-hand.1330 If, then, the forcefully acting agent succeeds in overcoming the natural inclination of the air to retain its volume, some parts of the air are moved outside the phial, thus prompting the remaining parts inside to expand against their nature. If the phial, whose mouth was subsequently blocked with a finger, is then immersed in water, and if, further, the finger covering its mouth is removed, one can witness how some water is sucked into the phial through the force of the inclination that belongs to the unnaturally expanded air, whose nature is actively striving to bring it back to its natural volume, so that, once the air returned to its natural volume and its natural quantitative state (ʿāda ilā qiwāmihī), we find some water having been attracted into the phial now making up for the missing parts of the original amount of air.

The notion of the surface enters the picture, when we realise that once the phial’s mouth has been blocked, part of the surface of the unnaturally enlarged air was in immediate contact with part of the surface of the finger, while the rest of the air’s surface still adhered to the inner surface of the phial. The air’s inclination, however, was not able to pull the rather solid body of the finger inside the phial. Thus, it had to remain in its unnaturally enlarged state. When, however, upon re-opening

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