Book of the Cure

The aim is to explore in detail the neglected issue of the system of the sciences as instantiated in the earliest examples of philosophical encyclopaedias, those penned by the Arabophone Persian polymath Avicenna (Ibn Sīnā, d. 1037). The research will be focused on Avicenna’s main and foremost summa, the Book of the Cure/Healing [Kitāb al-Šifāʾ], a wide-ranging and comprehensive work on Aristotelian philosophy that covers materials spanning from logic to metaphysics, with long intermediate sections devoted to natural philosophy and mathematics, pure and applied. The vastity of Avicenna’s magnum opus, together with the quality and the theoretical sophistication of his elaboration of Aristotle’s material, have until now discouraged a systematic study of the structure of the K. al-Šifāʾ. For medieval encyclopaedias of philosophy, the generally interesting problem of the ordering and organization of the sciences becomes however even more challenging, since the ordo sciendi is there thought to be a somewhat faithful mirror of a universal ordo essendi. Such a programmatic correspondence between the epistemological and the ontological levels invites to recognise in the structure of the summae the watermark of an analogous order of the world itself, in a fruitful exchange between the text and the reality it describes. The methodology proposed is that of a veritable mapping of the nodal points of juncture of Avicenna’s summa of philosophy: by charting systematically all the cross-references between different parts of the K. al-Šifāʾ, and by comparing them with those appearing in shorter philosophical summae also penned by Avicenna, SPACE will be able to show the geography of the philosophical landscape envisaged by the greatest thinker of the Islamic Middle Ages, allowing new insights into its theoretical landmarks. Before and beyond the ever-increasing sectoring of today sciences, such a map can offer the fascinating historical alternative of a holistic model of knowledge.

In my dissertation, I focus on two concepts that are important for understanding the way Avicenna (c. 980-1037) conceived the natural world, namely the continuum and the infinite. These concepts are strictly interconnected and were used by Avicenna to describe the physical structure of natural bodies. To more specifically understand what Avicenna meant by these two notions, it is necessary to consider one of the most important works of his, namely the Book of the Cure (or Book of the Healing), in Arabic Kitāb al-Šifāʾ or Šifāʾ. This is Avicenna’s vastest philosophical summa, covering almost all the principal branches of science known at the time. The second part of the Šifāʾ is entirely devoted to natural philosophy, and it is divided into eight sections. The first of these is the Physics (in Arabic al-Samāʿ al-ṭabīʿī), where Avicenna discusses and develops the most relevant and interesting doctrinal points found in Aristotle’s Physics. The Physics of the Šifāʾ is divided into four treatises. The most relevant for understanding what Avicenna thought about the continuum and the infinite is the third one. This treatise is entirely focused on natural bodies and their physical states, considered from the point of view of quantity. Among the quantitative states, or properties, of physical bodies, a prominent role is played by the continuum and the infinite. For this reason, in my dissertation, I focus specifically on this third treatise of the Physics of the Šifāʾ: I quote, translate from Arabic into Italian, and analyse the most significant passages dealing with these two physical notions.
According to Avicenna, the continuum is the only possible way to describe the structure of natural bodies from a quantitative point of view. Their quantity is continuous, not discrete. Through a long and complex discussion about the different meanings of the term “continuous”, Avicenna provides a systematic account of this notion, which discusses and develops Aristotle’s one.  What emerges from his account is that, according to Avicenna (and Aristotle), the most relevant property concerning the continuum is its infinite divisibility or divisibility ad infinitum. In this perspective, natural bodies cannot be considered aggregates of indivisible parts, which means that they cannot be composed of atoms. Bodies must have parts that are always further divisible or divisible ad infinitum. This does not imply that physical bodies are made up of an infinite number of parts. The parts inside the continuum do not exist in actuality, but only in potentiality. I focus on how Avicenna, resuming and enriching Aristotle’s position, illustrates these characteristics of the continuum.
The fact that natural bodies are infinitely divisible is something that also affects our understanding of them as moving bodies. Just like Aristotle, Avicenna maintains that a body would not be able to move if it were indivisible. I focus on the way Avicenna proves this thesis. The argument he provides is an original revised version of the proof adduced by Aristotle, which Avicenna found problematic. 
The fact that a moving body should be infinitely divisible is something that it shares with the other fundamental structures of the physical world – namely, the distance the body covers when it is moving, the time during which it moves and the motion itself. Therefore, for Avicenna, distance, time and motion, just like the moving body, all share the same structure and are all continuous and infinitely divisible. I explain how Avicenna argues for their isomorphism, taking up Aristotle’s discussion on the same topic.
Avicenna’s entire investigation into the continuum is permeated by the idea that something continuous is infinitely divisible. This raises the need to deal with the question of how exactly Avicenna conceived of the infinite, and what place he assigned to it in the framework of his natural philosophy. For this reason, I devote a substantial part of my dissertation to the discussion of how Avicenna understood the notion of the infinite.
Avicenna carries out an attentive and innovative analysis of all the possible meanings of infinity. He systematizes and widens the meanings already envisaged by Aristotle in his Physics. Some of them are ruled out – for example, the infinite understood as something extended without limit. Avicenna provides a long series of arguments to show that an infinitely extended body could neither exist nor move in the natural world. This is something Aristotle himself had argued for. However, most of the arguments presented by Avicenna are original and go far beyond what Aristotle had said in his Physics and De caelo.
Even though Avicenna does not accept this meaning of the infinite, this does not mean that he completely dismisses the infinite as a tool for understanding the natural word. On the contrary, one has just to conceive it in a different way, namely not as a state of infinite extension, but as a property that involves a process of addition or division. Something will be infinite by addition or infinite by division, if a process of infinite addition or infinite division can take place in relation to it. Infinite division is particularly important, because – as already noted – it is the kind of infinite that plays a role in the infinite divisibility of the continuum. As far as the infinite by addition is concerned, both Aristotle and Avicenna think that only numbers can be infinite in this way, while physical magnitudes cannot. However, once again, there are some important differences between their accounts. In particular, I argue that Avicenna does not agree with the way in which Aristotle had proved that magnitudes cannot be infinite by addition.
Following this, I investigate the problematic and controversial topic of the kind of existence attributed to the infinite: does it exist in potentiality or in actuality in the natural world? This issue was discussed by Aristotle in some very difficult passages, which have induced modern scholars to come up with widely divergent interpretations. Avicenna considers all aspects of this problematic issue. He provides a complete and systematic picture, explaining in what sense the infinite can be regarded as existing in potentiality, in what sense in actuality and in what sense in neither of these ways.
Finally, Avicenna had to face a problem that arises when one considers the infinite divisibility of physical bodies. Since physical bodies are considered continuous and therefore infinitely divisible, it should be possible to divide them into parts that are indeterminately small. However, it is unclear whether a body, when it becomes extremely small through this division, retains the characteristics that were peculiar to it, prior to the division. I focus on what Avicenna thought about this issue, considering whether it was necessary to fix a minimum for each kind of body beyond which the latter cannot shrink and at the same time continue to be that specific body. It has been correctly suggested that, in dealing with this issue, Avicenna was probably thinking of certain observations made by the Greek commentators on Aristotle in Late Antiquity. However, it is also possible to see how Avicenna deepened their reflection, by adding further observations on the physical implications of positing minima naturalia.
In conclusion, my analysis of the notions of the continuum and the infinite in Avicenna’s Physics sheds light on many aspects of his way of conceiving physical bodies. By examining his treatment of these two crucial notions, it is possible to perceive, for example, how Avicenna argued that bodies cannot be constituted of atoms, but must be infinitely divisible, and that, in order to move, they cannot be indivisible or infinitely extended. Therefore, a complex picture of natural bodies emerges from my analysis. The latter has also offered me the opportunity to examine in greater detail the way in which Avicenna set himself in constant and original dialogue with Aristotle and the late-antique Greek philosophical tradition, particularly in relation to these crucial points in the natural philosophy of the Antiquity and the Middle Ages.

In metaphysics, Avicenna refers to the heaven as animal (ḥayawān), and to its proximate principle of motion as soul (nafs), by using the same terminology used in psychology to refer to sublunary animals and their principle. The strategy behind this approach is to account for a remote phenomenon, i.e. heavenly circular motion, through the account of an analogous but closer and thus more knowable phenomenon, i.e. animal locomotion. Thus, in metaphysics a sort of continuity between sublunary and celestial ‘animals’ seems to be posited: both are defined by means of the same terminology and share some distinctive features. However, in psychology, where this terminology is defined, Avicenna explicitly denies that sublunary and celestial ‘animals’ can be referred to in the very same way, except by equivocation. This position rests on the discontinuity between the sublunary and celestial realm that is posited in psychology.
Given that Avicenna’s attitude towards this issue is not consistent, the aim of this paper is to shed some light on the use of the terms animal and soul in psychology and in metaphysics, in order to ascertain whether they have the same meaning when they are applied to celestial and sublunary entities.

The present article analyzes the evidence available in Arabic sources (preliminary lists of contents in manuscripts; texts of manuscripts; later quotations) that supports the hypothesis according to which the Medieval Latin translation of the metaphysics of Avicenna’s Kitāb al-Šifāʾ is rooted in its Arabic background when it conveys an account of treatise V of the work (called “Versio Latina”) alternative to the one that can be found in the majority of codices and in current printings (“Versio Vulgata”). It is argued (i) that the Versio Latina is probably more original than the Versio Vulgata, for doctrinal and philological reasons; (ii) that the Versio Vulgata might respond to a deliberate intention to make the content of treatise V more compliant with the account of universals provided by Avicenna himself in the logic of the Šifāʾ and, in general, with the traditional pre-Avicennian ways of expounding the doctrine of universals; (iii) and that the Versio Vulgata was likely the product of Avicenna’s school, rather than of Avicenna himself, as the result of shared concerns and theoretical debates that prompted the decision of modifying Avicenna’s original text through the intervention, in all likelihood, of al-Ǧūzǧānī. Two further issues are conclusively discussed: (iv) how precisely the Latin translation relates to the Arabic background of the Versio Latina, (v) and whether the Versio Latina can be taken as the outlook of treatise V intended and licensed by Avicenna, or it also conveys elements of later, non authorial modifications.