John Philoponus (also known as John the Grammarian) was a late ancient thinker and Aristotlian commentator, who is remarkable for the originality of his ideas and novelty of his interpretations. Instead of defending Aristotle’s theory of place in his Commentary on Aristotle’s Physics, Philoponus argues for his own theory of place as a self-subsistent, incorporeal, three-dimensional extension distinct from bodies.
In his well-structured book, Ioannis Papachristou analyses Philoponus’ Corollaries on place and void (a section of his Commentary) in order to explain Philoponus’ account of place. Place is an important topic for Aristotle’s physics since it plays a role in understanding his theories of locomotion, the theory of cosmic order, the places of the elements, and void. The book examines Philoponus’ criticisms of these Aristotelian theories as well as his own theory of place as an incorporeal extension, and stresses the fundamental innovation of Philoponus’ concept of place. The book attempts (1) to consider Philoponus’ theory in the context of ancient discussions of place and void, especially in the Peripatetic tradition, (2) to reveal Philoponus’ grounds for his criticism of Aristotle and Themistius, and (3) to show how the new definition of place allows Philoponus to solve the problems of place and motion discussed in ancient physics.
The author esteems both the novelty of Philoponus’ theory in the context of the ancient tradition and the force of his arguments based on empirical observations and thought experiments. However, while the author contrasts Philoponus’ theory, which he describes as clear and reasonable, with Aristotle’s, which he marks as obscure and vague, he emphasizes that the main point of Philoponus’ theory is not to reject Aristotle’s account but rather to resolve the problems of the Aristotelian theory of place.
The book consists of five chapters. In the first chapter, the author analyzes the form and structure of Philoponus’ commentary, rightly assuming that the form of the text and the method of inquiry are related to its content. More precisely, he considers how Philoponus divides Aristotle’s text and discusses the structure of the corollaries. He summarizes six ways in which Philoponus explains Aristotles’ arguments and divides the Commentary into three structural parts: exegesis, critical observations, and digressions. The chapter also explains the order of polemical arguments in the corollaries, showing how Philoponus’ arguments focus on rejecting Aristotelian account of place and defending his own conclusions against opponents such as Alexander of Aphrodisias, Themistius, the Stoics, and the Atomists.
In the second chapter, the author provides a useful review of the ancient theories on place and extension, mainly focusing on Aristotle’s account and its interpretation by Themistius, but also covering the positions of Alexander, the Stoics, and the Atomists. He explains how Philoponus clarifies and questions Aristotle’s arguments on place. The author’s principal aim in this chapter is to show that Philoponus’ theory differs in some fundamental respects from other theories of extension in antiquity. The most important innovations of his theory of place are: (1) the notion of place as an incorporeal, three-dimensional extension, which is ontologically distinct from the corporeal extension of bodies, and (2) the claim that the existence of place is independent of bodies. The notion of place as ontologically distinct from the corporeal extension of body allows Philoponus to avoid the paradox of multiple coinciding place, since the parts of a body cannot collide with the parts of its place, in so far as place is incorporeal. It is thus impossible that place is the cause of the division of bodies, since division does not follow from incorporeal extension, but from matter.
The third chapter presents the core of Philoponus’ theory on place. The author summarises three kinds of arguments on the nature of place in the Corollary: (1) deduction from empirical observations, (2) reasoning from thought experiments, and (3) philosophical explanation. Philoponus considers the nature of place to be extension, that is, three-dimensional extension. At the same time, place is independent of body and has its own reality, a reality of incorporeal three-dimensional extension. Nonetheless, it never exists without a body; on the contrary, place is always filled with bodies. The author distinguishes three types of place in Philoponus: (1) the place of a specific body, (2) the place of a whole cosmos, and (3) absolute space, i.e., place on its own. The place of a specific body is identical in extent with the body itself; thus Philoponus considers place as a measure of contained body. Insofar as place is a measure, incorporeal extension of place is identical to corporeal extension of a body. The place of the whole cosmos is discussed in connection with the thought experiment: will the extension of cosmic place survive if all bodies under heaven are removed? Although Philoponus denies the actual existence of empty extension, he insists that cosmic extension differs from the extension of all bodies in the cosmos. This means that, even if bodies are removed, cosmic extension will remain the same since we can mentally take out physical bodies, but we cannot take out the extension that they fill. Therefore, Philoponus reaches the ontological self-sufficiency of the incorporeal extension of place. This extension can be perceived by our thought not as a quality or quantity of body, but rather as something different from bodies. Due to this difference, place is not destroyed along with body.
Thus, the author demonstrates that Philoponus’ concept of place as three-dimensional extension depends on corporeality, since Philoponus denies the existence of empty place as well as the existence of infinite extension, i.e., there is no place outside the heavens. However, place as such according to Philoponus is identical to void: absolute space is a void extension, which is not filled with bodies. The connection of place and void is discussed in more detail in the fourth chapter, while in the third he investigates Philoponus’ explanation of the power of place and the power of void.
The fourth chapter investigates Philoponus’ discussion of void and the relation between void and place. The author insists that Philoponus identifies absolute space with the void extension in the substrate, and defines void as a place without bodies. Furthermore, he considers Philoponus’ arguments on motion through void and defines this problem as a problem of the relationship between void and the full. Aristotle denies the possibility of motion through void, because he believes that bodies in void will necessarily be at rest or move with equal speed, which is impossible. According to Philoponus, the medium through which bodies move cannot be the cause of this movement and the void as a medium cannot affect the speed of a body. The speeds of bodies are unequal because there are different moving causes in them. The natural impulses of bodies which causes their motion does not cease to be in the void, therefore the speed of bodies is different. Although Philoponus agrees with Aristotle about the impossibility of the proportion of void and fullness, he shows that motion through void has a proportion to the motion through filled space, because time is proportional to time and distance to distance. He proposes to understand motion through void as a constant exchange of bodily positions within the extension of place. Thus, the relationship between void and fullness can be understood as a proportion of two incorporeal extensions, the bodiless extension and the extension filled with body.
In addition, Philoponus gives a new interpretation of locomotion. He demonstrates that place remains unmoved, while bodies change places reciprocally and move according to their own impulses. This mutual replacement is possible only due to the existence of unmoved void which is understood as an extension of place; however, at the same time, empty extension cannot be the cause of movement or affect it somehow. Thus, according to Aristotle, void has no place at all and is incompatible with the very possibility of movement, while in Philoponus’ thought it becomes identical with place as such and starts to be interpreted as a necessarily condition for locomotion.
Finally, in the fifth chapter the author gives a detailed examination of the Aristotelian account of place and Philoponus’ critique of Aristotle and the Peripatetic tradition. The author considers Aristotle’s account of place as a relativist model, for Aristotle’s place exists in relation to body only, and Philoponus’ account as a substantialist theory, for Philoponus insists on the ontological difference and independent existence of place. The author examines Philoponus’ arguments against the main points of Aristotle’s doctrine: (1) the definition of place as a limit of surrounded body, and (2) the sameness of place and body. Philoponus discusses the problems of Aristotle’s theory, namely motion through place and the place of the heavens, and proves that Aristotle’s definition of place as a limit of surrounding body leads to incorrect conclusions.
The concept of absolute space as a void of incorporeal extension that is common for all bodies allows Philoponus to (1) consider locomotion as a mutual replacement of bodies in the frame of the three-dimensional extension of place, which is limited by the heavens, (2) define the place of the heavens as a cosmic extension, and (3) discuss the order of elements not in connection with a power of natural place, but in connection with the natural impulses of the elements.
The structure of the book allows the author to present Philoponus’ doctrine on place in detail, and he explicates the content of that theory as well as the philosophical context of Philoponus’ doctrine and his critical arguments. This book focuses only on Philoponus’ Commentary on Physics and does not correlate the concept of place as an unlimited, incorporeal, and three-dimensional extension with Philopous’ concept of matter as a three-dimensional corporeal extension in De aeternitate mundi contra Proclum. Also, the author does not compare Philoponus’ discussion of the place of natural elements in his Commentary with his arguments on the nature and motion of elements in De aeternitate mundi contra Aristotelem. It seems that specialized scholarship has not yet analyzed Philoponus’ Corollary on place in detail, although this theory is a remarkable episode in the history of philosophy and science and is very important both for Philoponus’ philosophy and for ancient physics in general.
Overall, Papachristou’s book is a valuable contribution to the study of place, void, and extension in ancient physics in general and of Philoponus’ thought in particular. It offers readers a persuasive interpretation of Philoponus’ theory of place, adding perceptibly to our understanding of the discussion of place and void in ancient physics. Hopefully, it will stimulate further discussions of Philoponus’ notion of extension in his commentaries on Aristotle as well as in his polemical works.