Building directly on the linguistic elements and the language theory discussed in Chapter 2, Chapter 3 deals with the second level of lexis by focusing on the ἀρχὴ τῆς λέξεως (the foundation of lexis), i.e. Aristotle’s remarks regarding individuals’ use of linguistic elements as determined by sociolinguistic factors. The chapter has three sections, each of which examines Aristotle’s claims within lexis in a different social context.

The introduction asserts that the different causal, spatial, and comparative relations in Plato's Timaeus generated a model of knowledge that denies a strict separation between the disciplines. I contrast the dialogue's epistemic vision with the prevailing hierarchies of knowledge developed by ancient thinkers, including Plato himself, which ranks medicine below philosophy because it is a technē ('art'), deals with the body, and its practitioners were often enslaved or freedpersons. I argue that Galen's expansive refiguring of medicine's boundaries -- his 'boundary work' -- is part of a tactic to improve his profession's credibility and his own authority. After outlining my approach to science as a discursive practice, I consider how Galen's philosophical training enabled him to exploit the epistemic possibilities of the Timaeus, which seems to recognize that knowledge can be divided and bounded differently by each knower. I conclude by proposing that Galen’s own role in interfacing Arabic readers with the dialogue called for Arabic doctors and philosophers to reevaluate their own categories and taxonomies of knowledge, which had been shaped by late-antique epistemologies.

The first chapter of this book delineates the intellectual context in which Aristotle’s ideas on the concept of lexis developed, before focusing on his own definitions of the concept. The chapter is divided into four sections. The first threedeal with lexis in the works first of Plato,Isocrates and Aristotle respectively. The final section introduces the three levels into which lexis has been divided in this book.

Chapter 4, together with Chapter 5, focuses on the third level of lexis and the ἀρετὴ τῆς λέξεως (the excellence of lexis). Since Aristotle devotes much attention to this characteristic of lexis, the discussion of this third level of lexis has been divided into two chapters: Chapter 4 deals with the intra-textual aspect of Aristotle’s remarks on lexis as a means for the creation of different kinds of poetry and rhetoric, i.e. lexis as technē; in Chapter 5 extra-textual factors are considered and are followed by a discussion of the purpose and function of lexis on its third level.

Chapter 6 concludes the discussion of lexis by focusing on metaphor, the linguistic and stylistic element par excellence treated under the notion of lexis. Unlike other linguistic phenomena, metaphor is not tied to a single form or genre but is listed in every enumeration of linguistic means available to the author of a poetic or rhetorical composition. This final chapter highlights the reason for the special place Aristotle assigns to metaphor by looking at it from the point of view of lexis and by examining it in the light of the excellence of lexis, as well as of mimēsis and energeia. Not only does this allow for a new approach to metaphor, but it also highlights the benefits of a three-level approach to Aristotle’s concept of lexis.

The second chapter studies the efforts of the Christian Ḥunayn ibn Isḥāq, whose workshop in ʿAbbāsid Baghdad translated the Galenic sources considered in this book, to enhance the respectability of the specialism of ophthalmology in his Ten Treatises on the Eye. I show that, even more so than medicine, ophthalmology was at a disadvantage in its pursuit for epistemic authority because Galen himself had attacked the sub-field as an exemplar of the worrying tendency among doctors in Rome and other cities towards specialization, which threatened the unity of the discipline and the health of patients. Concerned with his own intellectual status at court, Ḥunayn, I argue, subversively uses Galen's explanation of the Timaeus' description of the eyes' service to the rational soul to give ophthalmologists a stake in medico-philosophical controversies relating to sensation. I also expose how Ḥunayn modifies Galen’s interpretation of Plato’s teleological ocular anatomy and visual theory in order to privilege the eye over all other organs as a window to cosmic knowledge.

Chapter 5 is a direct continuation of the stylistic features discussed in Chapter 4. Rather than focusing on intra-textual aspects, though, this chapter looks at the extra-textual factors medium, hypokrisis (delivery) and audience, all of which further influence lexis on its third level. The chapter finishes with an examination of the purpose and function of lexis on its third level.

Galen attempts to define the Timaeus as a medical resource to justify medicine’s right to comment on issues regarding the soul and the nature of life, to which philosophers had long laid claim. I call attention to Galen’s commentary On the Medical Statements in Plato’s Timaeus and the Arabo-Latin prologue to the Synopsis of Plato’s Timaeus to illustrate how his assertions that the dialogue contains ‘medical’ information allow him to draw more expansive boundaries for medicine. My analyses of On the Doctrines of Hippocrates and Plato and The Faculties of the Soul Follow the Mixtures of the Body reveal that Galen advances more monopolistic claims on the soul for medicine by appealing to his anatomical expertise and the dialogue's link between bodily and psychic disease to show the pertinence of his medical expertise to psychological controversies and ethics. I conclude with a discussion of Galen's interpretation of the Timaeus' account of vegetative sensation, which posits a homology between plants and humans that he exploits to extend medicine's boundaries beyond the world of the body.

Chapter five concentrates on the Rabbi Moses Maimonides' reformist project to rid Galenism of its Timaean elements. As I establish, while Maimonides' affiliation with Aristotelianism put him in conflict with Galen, the Platonic lines in Galen's thought also generated problems for his own conception of Jewish belief. I show that Maimonides rejected Galen's reading of the Timaeus' cosmogony as heterodox in the Guide for the Perplexed and Medical Aphorisms because of its denial of creation ex nihilo and the omnipotence of God. Therefore, Maimonides had theological reasons for wishing to curtail Galen's philosophical reach. Giving special attention to the Medical Aphorisms, I uncover the various polemical tactics that Maimonides employs, which include giving more limited meanings to Galen's philosophically loaded terminology and mobilizing his own anatomical experience to dispute Galen's brain-centred theory of sensation, to dephilosophize Galenism and recentre it on the body.

Chapter 2 begins with an outline of the four passages in which Aristotle introduces the three pillars of lexis and then moves on to two sections in which the first, i.e. ἅπασα λέξις (the entirety of lexis), is discussed. This first level of lexis includes the linguistic elements treated under the notion of lexis and Aristotle’s theory of language. These not only present Aristotle’s thoughts on language as an abstract system, but they also form the most fundamental level upon which the remainder of Aristotle’s thoughts on the concept of lexis are based.