Taneli Kukkonen Mind and Modal Judgement: Al-Ghazal¯ ¯ıand Ibn Rushd on Conceivability and Possibility

Recent meta-level examination of the practice of analytic philosophy has brought about a resurgence of interest in how conceivability is supposed to relate to possibility. It has been noted that contemporary philosophers of various stripes routinely engage in thought experiments of various kinds and that a remarkable—sometimes surprising— amount of confidence seems to be put in such imaginary exercises. A typical example is the way an appeal to the conceivability of a scenario is used to demonstrate the contingency of a given state of affairs; but more complex examples abound, and some have proved remarkably difficult to decipher.1 On what level and to what extent is such confidence warranted? Does a genuine connection exist between what we can think of and what is actually possible? And if so, what kind of bond is this? Many people would agree that conceivability bears some relation to what might be termed metaphysical possibility, as plainly it is less restrictive than garden-variety physical possibility, yet conceivability requires more than some thing’s being merely logically possible. Yet metaphysical possibility itself remains a vague category: if the lines cannot be drawn any more precisely than this, then the relationship remains basically unsettled. One way of approaching the problem would be to focus on the psychological mechanisms associated with conceptualisation. But this line of attack brings with it its own share of troubles. In an introduction to a recent volume on Conceivability and Possibility, Tamar Szabo Gendler and John Hawthorne note that one reason why contemporary discussions often appear ill-defined is that it is not at all clear what role conceivability could or should play in a naturalised epistemology and psychology. While our perceptual qualities are thought to enjoy a natural correspondence relation with features in the world around us and to fulfil a useful function in helping us navigate it, no such link is typically postulated as regards our imaginary or conceptual powers.2 The remark is instructive from a systematic standpoint, but for practitioners of the history of philosophy it carries especial significance. For although it is true that there

1 See Gendler & Hawthorne (2002); from a phenomenological standpoint, Le Doeuff (1989); for a feminist critique, La Caze (2002). 2 For these remarks, see Gendler & Hawthorne (2002) 3–6.

Vesa Hirvonen, Toivo J. Holopainen & Miira Tuominen (eds.), Mind and Modality: Studies in the History of Philosophy in Honour of Simo Knuuttila. Leiden: Brill, 2006. 122 taneli kukkonen is no consensus regarding the psychic faculties over and above the senses in much of modern philosophy (perhaps not regarding the senses themselves), the same cannot be said for the better part of the late ancient and medieval philosophical traditions. Due to the body of Aristotelian commentary building on the De anima and the small psychological treatises collected in the Parva naturalia, a relatively stable picture can be found in the late ancient and medieval traditions concerning the way the various sensory and cognitive capacities stack up and relate to each other. Especially after the consolidation efforts of Ibn Sina¯ (the Latin Avicenna, 980–1037)thepowersof imagination (Gr. phantasia) and intellectual conception (nous) occupy more or less fixed positions within this overall scheme.3 My intention in this small piece is to examine how the psychological notions of conceivability and imaginability map onto the question of possibility in one seminal piece of post-Avicennian Arabic philosophical debate. Because the exchange docu- mented in Abu¯ H. amid¯ al-Ghazal¯ ¯ı’s Incoherence of the Philosophers (Tahafut¯ al-falasifa¯ , 1095,henceforthTF)andAbual-Wal¯ ¯ıd Ibn Rushd’s, or the Latin Averroes’ Incoher- ence of the Incoherence (Tah¯ıfut al-tahafut¯ , 1180, TT ) is to a large extent predicated on al-Ghazal¯ ¯ı’s perception that an unwarranted necessitarianism pervades the Muslim philosophers’ worldview, divergent conceptions of possibility and necessity lie at the heart of al-Ghazal¯ ¯ı’s and Ibn Rushd’s debate concerning the eternity of the world.4 The broader question of what can be allowed (yujazu¯ ) in thought informs the Incoherence debates as a whole, as both al-Ghazal¯ ¯ı and Ibn Rushd repeatedly weigh in on what kinds of hypotheses constitute premises suitable for philosophical reflection.5 This in turn comes back to the conceivability and/or imaginability of unconventional (from the Aristotelian point of view) cosmologies, something on which the two thinkers seem constantly at odds.

1. Imagining Things

The link between conceivability and possibility is evoked right at the beginning of the Tahafut¯ debates, as al-Ghazal¯ ¯ı summarises what he takes to be the philosophers’ most salient proof for the world’s eternity. The proof posits a supposedly necessary connection between an agent which is forever immutable and the object of its actions; al-Ghazal¯ ¯ı parries with a disarmingly simple question.

3 See G. Strohmaier, “Avicennas Lehre von den ‘inneren Sinnen’ und ihre Vosassetzungen bei Galen”; reprinted in Strohmaier (1996) 330–341. 4 See Kukkonen (2000a, b). 5 This can be characterised as a discussion about the contradictory terms possibility and impossibility, as opposed to possibility and necessity.