TABLE OF CONTENTS
Preface
Introduction - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0001
[epistemology, Islamic sciences, Keplerian turn, liberal arts, physical optics, practical optics, retinal image, ray-geometry, universities, visual paradigm]
After setting out the basic historiographical context for the study that follows, this chapter provides a brief account of the book’s overall thesis, which emphasizes the sharp contrast between pre-Keplerian and post-Keplerian optics. That contrast, it is argued, lies in a fundamental difference in analytic focus. Pre-Keplerian optics was driven by the need to explain precisely how vision can yield a faithful mental picture of objective reality. Its ulterior focus was therefore on cognition-theory rather than light-theory. In post-Keplerian optics, on the other hand, the analytic focus was reversed, its primary aim now being to explain the physics of light rather than the epistemology of sight. The chapter ends with a fairly brief account of the sources and methods upon which the study unfolding in the succeeding eight chapters is based. (pages 1 - 22)
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The Emergence of Optics as a Science - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0002
[cathetus rule of image location, catoptrics, crystalline lens, equal-angles law, extramissionism, intromissionism, least distance principle, optic nerves, pneuma, visual ray]
This chapter explores how optics evolved as a science between roughly 350 BC and 160 AD according to three different, but roughly complementary, approaches. The first of these, the so-called philosophical approach, is exemplified in Aristotle’s account of visual perception, which was based on a range of psychological faculties from common sense, through imagination, to intellect. The second approach, which is epitomized in Euclid’s Optics and Catoptrics, was based on a geometrical analysis of sight according to visual rays. Its primary aim was therefore to account for spatial perception. The final approach, which is represented par excellence by Galen, looked to ocular anatomy and physiology for the explanatory basis of visual perception. (pages 23 - 75)
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1. Early Intimations
2. Physical and Psychological Theories of Vision
3. The Anatomical and Physiological Grounds of Vision
4. Theories of Color and Color Perception
5. The Euclidean Visual Ray Theory
6. Euclidean Catoptrics
7. Burning Mirrors and the Analysis of Focal Properties
8. Conclusion
Ptolemy and the Flowering of Greek Optics - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0003
[angle of refraction, diplopia, ghost images, method of first and second differences, magnification, moon illusion, plane of reflection, refraction, principle of reciprocity, reflection points]
The main purpose of this chapter is to show how Ptolemy combined all three approaches discussed in the previous chapter in order to create a theory of sight that accounts broadly not only for visual perception per se but also for visual misperception: i.e., visual illusions, which Ptolemy attributed to improper physical conditions, interference with the normal functioning of the visual system, or psychological deception. Two types of illusion—image-displacement and deformation according to reflection and refraction—were of paramount concern to Ptolemy, whose analysis of reflection and refraction in books 3-5 of the Optics remained more or less canonical until the seventeenth century. In fact, as claimed at the end of the chapter, Ptolemy set the agenda for optics as it developed until the early modern period, much as his Almagest set the agenda for astronomy. (pages 76 - 129)
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1. The Ptolemaic Account of Visual Perception
2. The Ptolemaic Account of Reflection
3. The Ptolemaic Account of Refraction
4. Atmospheric Refraction and the Moon Illusion
5. Conclusion
Greco-Roman and Early Arabic Developments - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0004
[agent intellect, burning mirrors, cone of light-radiation, divine illumination, faculty psychology, internal senses, Late Platonism, neoplatonism, potential intellect, actual intellect]
This chapter examines the post-Ptolemaic tradition of visual theory within the Late Platonist, or Neoplatonic, tradition between roughly 250 and 550. Marked by an effort to reconcile Platonic and Aristotelian thought on a variety of subjects, including perception and cognition, this tradition gave rise to a model of cognition that appealed strongly to eternal Forms, representative mental images, and intellectual illumination, which rendered those images cognitively “visible.” After looking at how this model evolved and how it affected the thought of St. Augustine, the chapter traces its influence on certain Arabic thinkers, such as al-Kindī, Ḥunayn ibn ʾIsḥāq, and al-Fārābī. Among these thinkers, Avicenna assumes pre-eminence for his faculty psychology based on the five internal senses in the brain. The chapter concludes with an examination of the ninth- and tenth-century revival of classical geometrical optics at the hands of al-Kindī, Aḥmad ibn ʿĪsā, and Qusṭā ibn Lūqā. (pages 130 - 180)
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1. Plotinus’s Theory of Visual Perception
2. The Later De anima Commentators
3. Saint Augustine’s Psychological Model: The Inward Ascent
4. The Arabic Transition: The De anima Tradition
5. The Arabic Transition: Geometrical Optics
6. Conclusion
Alhacen and the Grand Synthesis - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0005
[cognition by abstraction, angle of deviation, controlled experiment, faculty of discrimination, final sensor, particular forms, universal forms, perception through recognition, peripheral vision, vectorial analysis]
At the most general level, this chapter aims to show that Ibn al-Haytham’s Kitāb al-Manāẓir (“Book of Optics”) is best understood as a systematic elaboration on Ptolemy’s Optics according to a replacement of Ptolemy’s visual rays with light-rays. As part of that elaboration, Alhacen provided a more systematic operational account of visual perception according to its stages from brute, physical sensation, through visual discrimination and perception, to conception. This account, moreover, was based implicitly on a psychological model that was fully compatible with Avicenna’s internal senses model of faculty psychology. In addition, Alhacen’s use of ray-geometry to account for reflection and refraction, although still based on Ptolemy, was considerably more sophisticated and rigorous. Altogether, then, Alhacen’s theory of vision marks the perfection of ancient optics, as epitomized in Ptolemy’s Optics, not a revolutionary break with those optics. (pages 181 - 227)
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1. The Elements of Alhacen’s Analysis
2. Visual Discrimination, Perception, and Conception
3. Reflection and Its Visual Manifestations
4. Refraction and Its Visual Manifestations
5. Conclusion
Developments in the Medieval Latin West - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0006
[agent intellect, visual and animal spirit, intentional species, multiplication of species, perspectivist tradition, phantasm, simulacra, theophany, trivium, quadrivium]
This chapter traces the evolution of visual theory in the Latin West from late antiquity to around 1300. A key point in that evolution came in the twelfth century with the translation of ancient Greek as well as original Arabic works from Arabic to Latin. These works included Ibn al-Haytham’s Kitāb al-Manāẓir. Translated as De aspectibus around 1200 and attributed to Alhacen, this treatise formed the basis for derivative works by Roger Bacon, Witelo, and John Pecham, who are credited with establishing the so-called perspectivist tradition of medieval optics. Bacon is especially important in this regard because he explicitly meshed Alhacen’s operational and mathematical account of vision with Avicenna’s internal senses model of cognition. In doing so, he created a visual paradigm according to which the ocular and cerebral system produce increasingly abstract psychological and mental images, or intentional species, that faithfully represent the external reality from which they arise. (pages 228 - 277)
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1. Background to the Translation Movement
2. The Translation Movement and the Inroads of Aristotelianism
3. The Scholastic Analysis of Perception and Cognition
4. Geometrical Optics and the Evolving Science of Perspectiva
5. Conclusion
The Assimilation of Perspectivist Optics During the Later Middle Ages and Renaissance - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0007
[anamorphosis, artificial perspective, natural perspective, camera obscura, chiaroscuro, imagination, intuitive cognition, mirror analogies, optical anomalies, optical veils]
The primary focus of this chapter is on how the perspectivist visual paradigm, or certain elements of it, were disseminated not only through university teaching but also through preaching, literature, and painting. The result was the emergence of optical literacy, which in turn spawned a critical interest in optics among thinkers, such as Leonardo da Vinci, who were not formally educated but intellectually and empirically perceptive. Among other things, such critical interest led to increasing recognition of the shortcomings of the perspectivist paradigm in explaining such optical anomalies as artistic illusionism, which cannot be adequately accounted for by ray-geometry. (pages 278 - 321)
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1. Optics as a Quadrivial Pursuit in the Arts Curriculum
2. Theology and the Emergence of Optical Literacy
3. Optical Motifs in Literature
4. Renaissance Art, Naturalism, and Optics
5. Conclusion
The Keplerian Turn and its Technical Background - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0008
[focal point, image-inversion, image-projection, lens-theory, ray tracing, real images, virtual images, sense-object correspondence, spherical aberration]
This chapter examines the analytic and epistemological turn represented by Kepler’s account of retinal imaging. It starts with a look at the immediate context of that account in the optical work of such sixteenth-century thinkers as Francesco Maurolico and Giambattista Della Porta. Then, after a close look at the scientific reasoning behind Kepler’s theory, the chapter concludes with a brief look at the theory’s analytic and epistemological implications. The main point of this chapter is to show just how radically Kepler departed from his perspectivist sources in proposing the theory of retinal imaging. (pages 322 - 372)
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1. Technological, Social, and Cultural Changes: 1450– 1600
2. Rethinking Concave Mirrors and Convex Lenses
3. Rethinking the Eye
4. Kepler’s Analysis of Retinal Imaging
5. The Analytic Turn
6. The Epistemological Turn
7. Conclusion
The Seventeenth-Century Response - A. Mark Smith
DOI: 10.7208/chicago/9780226174938.003.0009
[corpuscularism, chromatic aberration, experimentum crucis, hyperboloidal lenses, least time principle, mechanism, mind-body dualism, pineal gland, longitudinal wave theory, speed of light]
The ways in which the Keplerian turn discussed in the previous chapter manifested itself during the seventeenth century is the subject of this chapter, which examines three particular developments influenced by that turn: the deployment and improvement of telescopes and microscopes; the emergence of new, mechanistic theories of light and color; and the resulting efforts to explain sensation, perception, and cognition on the basis of these new theories. One clear outcome of these efforts was a complete repudiation of the medieval “pictures-in-the-mind” approach to visual cognition, with its emphasis on animating spirits and intentional species, in favor of a more materialist approach based on physical impulses and reactions that correlate with such “pictures” without bearing any resemblance to them. (pages 373 - 416)
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1. The Conceptual and Cultural Context for the Keplerian Turn
2. Extending Vision in Both Directions
3. New Theories of Light
4. Recasting Color
5. The Epistemological Consequences
6. Conclusion
Bibliography
Index
