Summary
Euclid's "Phaenomena" argues that celestial bodies appear in their correct, upright positions despite their images being inverted on the retina. This phenomenon is explained by the eye's ability to form an inverted image of external objects on the retina. The book addresses how the viewer perceives objects as upright, even though the visual representation on the retina is reversed, and how the eye's structure, particularly the convexity of the cornea, is crucial for converging light rays to form this image.
The text discusses the role of the eye's various parts in vision, referencing the contributions of figures like Fryar Bacon and Joannes Keplerus. It touches on the reasons for the white color of certain tunicles of the eye, suggesting it enhances the visibility of the pupil and iris, aiding in judging the direction of gaze, a concept Keplerus observed.
Key concepts
- Inverted Order — The phenomenon where images of visual objects are painted on the retina in a reversed orientation.
- Convexity of the Cornea — The curved surface of the cornea that enables the convergence of light rays to form an image on the retina.
- Erect Appearance of Objects — The perception of objects as upright, despite their inverted representation on the retina.
- Picture on the Retina — The inverted image formed on the retina by light rays from external objects.
From the book
IN TWO VOLUME S. By WILLIAM PORTERFIELD, M. D. Fellow of the Royal College of Phy s icians at Edinburgh . VO L. I. —Whence is it that Nature doeth nothing in vain, and whence ari s es all that Order and Beauty we s ee in the World? —— How came the Bodies of Animals to be contrived with s o much Art, and for what Ends were their s everal Parts? Was the Eye contrived without s kill in Optics, and the Ear without knowledge of Sounds? &c. Newton 's Opticks , Query 28. EDINBURG H: Printed for A. Miller at London . and for G. Hamilton and J. Balfour at Edinburgh . M,DCC,LIX. TO Sir Alexander Dick of Prestonfield , Baronet, PRESIDEN T, AND TO The COUNCIL and FELLOWS OF THE Royal College of PHYSICIANS AT EDINBURG H: This Treatise on the Eye , &c. is most humbly Dedicated, By their most Obedient…
← Errata A Treatise on the Eye: The Manner and Phænomena of Vision ( 1759 ) by William Porterfield Plates → 4967160 A Treatise on the Eye: The Manner and Phænomena of Vision — Plates 1759 William Porterfield
Popular questions readers ask
- How would you explain Porterfield's central claim that the eye's "Structure and Mechanism discovers more Art and Design" than any other body part, without using his exact words? What specific details from the text illustrate this concept for a layperson?
- The excerpt begins with a quote from Newton's Opticks, raising questions about Nature's contrivance. What foundational philosophical or theological perspectives on the natural world does Porterfield's treatise seem to build upon, and how might these influence his scientific observations and conclusions about the eye?
- Porterfield outlines many practical benefits of vision, from choosing food to avoiding danger. Beyond these functional aspects, what deeper, perhaps less tangible, human experiences or societal developments do you infer Porterfield believes are fundamentally enabled or shaped by the sense of sight?
- How might a contemporary biologist, informed by modern understanding of genetics and evolution, articulate the "mechanism" and "contrivance" of the eye differently from Porterfield in 1759? What specific terms or concepts from Porterfield's description would likely be reinterpreted or challenged, and why?
- Porterfield praises the eye as "magnificent and curious as the Sense is useful and entertaining." If you were to analyze another complex biological organ using these same criteria, what specific features would you highlight to argue for its equivalent "magnificence," "curiosity," "usefulness," and "entertainment" value, according to Porterfield's framework?