ArgumentHermann von Helmholtz’s distinction between “pure intuitive” and “physical” geometry must be counted as the most influential of his many contributions to the philosophy of science. In a series of papers from the 1860s and 70s, Helmholtz argued against Kant’s claim that our knowledge of Euclidean geometry was an a priori condition for empirical knowledge. He claimed that geometrical propositions could be meaningful only if they were taken to concern the behaviors of physical bodies used in measurement, from which it (...) followed that it was posterior to our acquaintance with this behavior. This paper argues that Helmholtz’s understanding of geometry was fundamentally shaped by his work in sense-physiology, above all on the continuum of colors. For in the course of that research, Helmholtz was forced to realize that the color-space had no inherent metrical structure. The latter was a product of axiomatic definitions of color-addition and the empirical results of such additions. Helmholtz’s development of these views is explained with detailed reference to the competing work of the mathematician Hermann Grassmann and that of the young James Clerk Maxwell. It is this separation between 1) essential properties of a continuum, 2) supplementary axioms concerning distance-measurement, and 3) the behaviors of the physical apparatus used to realize the axioms, which is definitive of Helmholtz’s arguments concerning geometry. (shrink)

Significantly, Berkeley, in his Essay Towards a New Theory of Vision, leveled a sustained attack on just this geometrical theory of distance perception. At first glance it may seem, as it did to Berkeley, that Descartes’ geometrical theory is produced by a simple error: namely, by the idea that a physiological optics provides an adequate description of the psychological processes of judging distances. In truth, this is the weakest of Berkeley’s objections to Descartes’ theory. Obviously we do not (...) see the angles and lines of convergence when we focus on a distant object, nor are we aware of having used any geometrical rules in judging distance. And Descartes never claimed this. (shrink)

This book explores the interrelationships between optics, vision and perspective before the Classical Age, examining binocularity in particular. The author shows how binocular vision was one of the key juncture points between the three concepts and readers will see how important it is to understand the approach that scholars once took. In the Middle Ages and the Renaissance, the concept of Perspectiva – the Latin word for optics – encompassed many areas of enquiry that had been viewed since (...) antiquity as interconnected, but which a erwards were separated: optics was incorporated into the field of physics (i.e., physical and geometrical optics), vision came to be regarded as the sum of various psycho-physiological mechanisms involved in the way the eye operates (i.e., physiological optics and psychology of vision) and the word ‘perspective’ was reserved for the mathematical representation of the external world (i.e., linear perspective). The author shows how this division, which emerged as a result of the spread of the sciences in classical Europe, turns out to be an anachronism if we confront certain facts from the immediately preceding periods. It is essential to take into account the way medieval scholars posed the problem – which included all facets of the Latin word perspectiva – when exploring the events of this period. (shrink)

The historical antecedents of Frege's treatment of binocular vision in "The thought" were the physiological writings of Johannes Mueller, Hermann von Helmholtz, and Emil du Bois-Reymond. In their research on human vision, logic was assigned an unexpected role: it was to be the means by which knowledge of a world extended in three dimensions arises from stimuli that are at best two-dimensional. An examination of this literature yields a richer understanding of Frege's insistence that a proper epistemology requires us (...) to recognize the existence and importance of nonsensible sources of knowledge. (shrink)

A number of ordinarily separate disciplines--e.g., physics, physiology, psychology--are here brought together in an effort to reconstitute optics as the complete science of human vision, thus replacing classical optics which dealt with vision only under perfect conditions. The emphasis is primarily scientific rather than philosophical.--R. G. S.

Newton began his optical studies believing in the modification theory, which was still universally accepted at that time, and in the perception of colour as a physiological process—a process in which the eye responds differently to the different velocities of identical globules. His discovery that white light is heterogeneous led him to switch to considering colour in purely physical terms.A century later, Goethe started out by accepting Newton's physical theory. He soon abandoned it, however, finding modification to be more (...) in keeping with his own insights. One beneficial consequence of this was that he developed an awareness of the importance of the physiological aspect of colour perception, and was therefore able to demonstrate that Newton's theory of light and colours is too simplistic; that there is more to colour than variable refrangibility. (shrink)

The modern physiological optics introduces the notions related to the conditions of fusion of bi- nocular images by the concept of correspondence, due to Christiaan Huygens (1704), and by an experiment attri- buted to Christoph Scheiner (1619). The conceptualization of this experiment dates, in fact, back to Ptolemy (90- 168) and Ibn al-Haytham (d. af. 1040). The present paper surveys Ibn al-Haytham's knowledge about the mecha- nisms of binocular vision. The article subsequently explains why Ibn al-Haytham, a mathematician, (...) but here an experimenter, did not give the circular figure of the theoretical horopter, construction due to Gerhard Vieth (1818) and Johannes Müller (1826). But, on the other hand, it is clear that Ibn al-Haytham's experimental study puts in place the notion of corresponding points, the cases of homonymous and cross diplopia, and even prepares the discovery of Panum area. L'optique physiologique moderne introduit les notions relatives aux conditions de fusion des images binoculaires par le concept de correspondance, prêté à Christiaan Huygens (1704), et par une expérience attribuée à Christoph Scheiner (1619). L'article montre que la conceptualisation de l'expérience remonte en fait à Ptolémée (90-168) et à Ibn al-Haytham (m. ap. 1040), et précise les connaissances que ce dernier avait des mécanismes de la vision binoculaire. Il est ensuite expliqué pourquoi Ibn al-Haytham, mathématicien mais ici expérimentateur, ne donne pas la forme circulaire de l'horoptère théorique, dont la construction revient à Gerhard Vieth (1818) et Johannes Müller (1826). En revanche, l'étude expérimentale d'Ibn al-Haytham met en place la notion de points correspondants, les cas de diplopie homonyme et croisée et prépare même la découverte de l'aire fusionnelle de Panum. (shrink)

Thomas Reid claims to have learned of Idomenians, “an order of beings” in “sublunary regions” whose visual system is very much like ours except that they could detect only the direction of rays reaching their eyes, not the distance of origin. The properties of Idomenian vision are here examined in the light of the physiological optics of Reid’s time and of the scientific developments that have since augmented our knowledge of the discipline.

Modern color science finds its birth in the middle of the nineteenth century. Among the chief architects of the new color theory, the name of the polymath Hermann von Helmholtz stands out. A keen experimenter and profound expert of the latest developments of the fields of physiological optics, psychophysics, and geometry, he exploited his transdisciplinary knowledge to define the first non-Euclidean line element in color space, i.e., a three-dimensional mathematical model used to describe color differences in terms of (...) color distances. Considered as the first step toward a metrically significant model of color space, his work inaugurated researches on higher color metrics, which describes how distance in the color space translates into perceptual difference. This paper focuses on the development of Helmholtz’s mathematical derivation of the line element. Starting from the first experimental evidence which opened the door to his reflections about the geometry of color space, it will be highlighted the pivotal role played by the studies conducted by his assistants in Berlin, which provided precious material for the elaboration of the final model proposed by Helmholtz in three papers published between 1891 and 1892. Although fallen into oblivion for about three decades, Helmholtz’s masterful work was rediscovered by Schrödinger and, since the 1920s, it has provided the basis for all subsequent studies on the geometry of color spaces up to the present time. (shrink)

Back to Kant is a study of the rise of the neo-Kantian movement from its origins in the 1850s to its academic preeminence in the years before World War I. Thomas E. Willey describes early neo-Kantianism as a reaction of scientists and scientific philosophers against both the then discredited Hegelianism and Naturphilosophie of the preceding era and the simplistic and deterministic scientific materialism of the 1850s. "Back to Kant" was the slogan of a revolt against theories of knowledge which seemed (...) inadequate to recent discoveries in thermodynamics, physiology, optics and other fields. Because Immanuel Kant was the philosopher who placed Newtonian physics on new epistemological foundations and demonstrated the possibility of universal scientific truth, he was the right thinker for a generation of scholars living through a new scientific revolution in Germany and dissatisfied with both speculative idealism and crude materialism. The second wave of neo-Kantians continued to discuss problems of scientific epistemology in the 1880s and after, but they also showed a keen interest in political and social matters, attempting to bridge liberalism and socialism with Kantian ethics. Neo-Kantians had to face questions of socialism, the place of the working class in society, the phenomenon of social welfare, the challenge of political democracy. Willey uses the biographical approach to develop the relationship between unity and diversity in the movement, and to underscore the importance of personality in history. While individual dissertations and monographs have been written on various thinkers and schools within neo-Kantianism, this is the first wide-ranging history of the entire phenomenon. Willey observes that the movement did succeed in reasserting ethical values and in separating humanistic studies from the methods of physical science. He also discusses the possibility that a wider acceptance of neo-Kantian ideals among bourgeois intellectuals and socialist leaders might have reduced class antagonisms and sustained a stronger feeling of community between Germany and the West. (shrink)

During the second half of the 19th century, in the field of physiological optics, there was a strong controversy between Hermann von Helmholtz and Ewald Hering. This controversy has been usually characterized as “empiricism” vs. “nativism”. In the field of physiology of visual perception, several subjects demanded attention, among them, color vision. Helmholtz and Hering suggested different theories for the physiological correlate of color sensation and different color spaces to give an account of the relationships between colors. (...) In this article, I will argue that the controversy between the two authors could be understood as differences between styles of reasoning, and these different styles express different presuppositions. More specifically, I want to suggest that the disagreements could be linked to the discussions on how vital phenomena should be studied. (shrink)

Malevich’s main Suprematist works, such as ›Black Square‹, ›Black Circle‹, and ›Black Cross‹ from 1915, consist of black shapes on white ground. Surprisingly this series of shapes strongly resembles scientific black-and-white images used for research on colour theory, physiological optics, and psychology throughout the 19th century. This paper examines the parallels between Malevich’s paintings and the scientific drawings in three steps: It first characterizes black-and-white images in general, using Edmund Husserl’s definition of the term ›contrast‹. Secondly, the paper (...) investigates the development and function of black-and-white images as tools of perception in the sciences. It finally discusses the specific knowledge generated through Malevich’s art and through scientific black-and-white images, following Max Scheler’s phenomenological identification of knowledge. (shrink)

Rafael Malach is currently a professor in the department of Neurobiology at the Weizmann Institute in Israel. His current research is aimed at understanding how the neuronal circuitry in the human brain translates a stream of sensory stimuli into meaningful perception. Rafael Malach received his PhD in physiological optics from UC Berkeley and did his post-doctorate research at MIT. Originally doing research on the organization of neuronal connections in the primate brain, his focus has recently shifted to the (...) study of the human cerebral cortex using fMRI. Professor Malach has begun this research at Massachusetts General Hospital, exploring a new object-related region called the lateral occipital complex. Since then he expanded this research, studying the human visual cortex using a variety of methods, including adaptation paradigms, backward masking, and more recently naturalistic stimuli--all aimed at deciphering the intriguing link between perceptual experience and brain activity. (shrink)

The doctrine of primary qualities is commonly explained as science's return to a former ideal of mathematical intelligibility and as a sacrifice of the notion that we can be certain about what we perceive. According to the standard chronicle modern scientific explanations appeal to geometrically intelligible, yet theoretically imperceptible, particles. This thesis gains plausibility only by suppressing the role of physiological optics in the development of modern science. Descartes presented an original and significant theory of scientific observation in (...) his Dioptrics; according to which, correct perceptual judgments can be made about the spatial qualities of any body, even about bodies so small as to be imperceptible under ordinary circumstances. This theory insured the perceptual accessibility of the spatial qualities of minute bodies but failed, as Locke discovered upon adding solidity to the list of primary qualities, to explain access to non-spatial qualities. As a result of the failure of Descartes' theory of perception to give an adequate account of scientific observation, Locke took the position that solidity or impenetrability cannot ordinarily be perceived, but rather that it can be and is regularly detected by experiment. This Lockean shift from direct perceivability of spatial qualities to the experimental detection of "new" primary qualities marks an important step in the methodological development of early modern science. (shrink)

This article is in three parts. Part I gives an account of Erwin Schrödinger's growing up and studies in Vienna, his scientific work—first in Vienna from 1911 to 1920, then in Zurich from 1920 to 1925—on the dielectric properties of matter, atmospheric electricity and radioactivity, general relativity, color theory and physiological optics, and on kinetic theory and statistical mechanics. Part II deals with the creation of the theory of wave mechanics by Schrödinger in Zurich during the early months (...) of 1926; he laid the foundations of this theory in his first two communications toAnnalen der Physik. Part III deals with the early applications of wave mechanics to atomic problems—including the demonstration of equivalence of wave mechanics with the quantum mechanics of Born, Heisenberg, and Jordan, and that of Dirac—by Schrödinger himself and others. The new theory was immediately accepted by the scientific community. (shrink)

The quantitative experimental scientific psychology that became prominent by the turn of the twentieth century grew from three main areas of intellectual inquiry. First and most directly, it arose out of the traditional psychology of the philosophy curriculum, as expressed in theories of mind and cognition. Second, it adopted the attitudes of the new natural philosophy of the scientific revolution, attitudes of empirically driven causal analysis and exact observation and experimentation. Third, it drew upon investigations of the senses. Natural philosophical (...) disciplines such as optics and acoustics treated the functioning of the senses. Optics, in particular, had from antiquity comprised a complete theory of vision, combining the physics, physiology, psychology, metaphysics, and epistemology of vision, using mathematical techniques where feasible. Within medicine, sensory physiology examined anatomy, physiology, and pathology. Philosophical psychology had long examined the senses as mental capacities connected with cognition and knowledge, and such discussions also heeded the new attitudes of natural philosophy. This chapter first examines the early relations of psychology to biology and characterizes various eighteenth-century loci of psychological thought. It then pursues nineteenth-century developments in Germany and Britain that culminate in the “new” psychology of the 1860s and 1870s. (shrink)

The physiological blind spot corresponds to the optic disc where the retina contains no light-detecting photoreceptor cells. Our perception seemingly fills in this gap in input. Here we suggest that rather than an active process, such perceptual filling-in could instead be a consequence of the integration of visual inputs at higher stages of processing discounting the local absence of retinal input. Using functional brain imaging, we resolved the retinotopic representation of the physiological blind spot in early human visual (...) cortex and measured responses while participants perceived filling-in. Responses in early visual areas simply reflected the absence of visual input. In contrast, higher extrastriate regions responded more to stimuli in the eye containing the blind spot than the fellow eye. However, this signature was independent of filling-in. We argue that these findings agree with philosophical accounts that posit that the concept of filling-in of absent retinal input is unnecessary. (shrink)

Experiential and behavioural aspects of emotions can be measured readily but developing a contactless measure of emotions’ physiological aspects has been a major challenge. We hypothesised that different emotion-evoking films can produce distinctive facial blood flow patterns that can serve as physiological signatures of discrete emotions. To test this hypothesis, we created a new Transdermal Optical Imaging system that uses a conventional video camera to capture facial blood flows in a contactless manner. Using this and deep machine learning, (...) we analysed videos of the faces of people as they viewed film clips that elicited joy, sadness, disgust, fear or a neutral state. We found that each of these elicited a distinct blood flow pattern in the facial epidermis, and that Transdermal Optical Imaging is an effective contactless and inexpensive tool to the reveal physiological correlates of discrete emotions. (shrink)

A model of human consciousness is presented here in terms of physics and electronics using Upanishadic awareness. The form of Atman proposed in the Upanishads in relation to human consciousness as oscillating psychic energy-presence and its virtual or unreal energy reflection maya, responsible for mental energy and mental time-space are discussed. Analogy with Fresnel’s bi-prism experimental set up in physical optics is used to state, describe and understand the form, structure and function of Atman and maya, the ingredients of (...) human consciousness. A description of phases of mind in terms of conscious states and transformation of mental energy is given. Four states of consciousness and four modes of language communication and understanding processes are also given. Implications of above scientific awareness of Upanishadic wisdom to the modern scientific fields of physiological psychology, cognitive sciences, mind-machine modeling and natural language comprehension are suggested. -/- . (shrink)

As the word “optics” was understood from antiquity into and beyond the early modern period, it did not mean simply the physics and geometry of light, but meant the “theory of vision” and included what we should now call physiological and psychological aspects. From antiquity, these aspects were subject to geometrical analysis. Accordingly, the geometry of visual experience has long been an object of investigation. This chapter examines accounts of size and distance perception in antiquity (Euclid and Ptolemy) (...) and the Middle Ages (Ibn al-Haytham), before turning to "natural geometry" in Kepler and Descartes. It finds a purely mechanical realization of natural geometry in Descartes (primarily in his L'Homme, 1664), in which he conceives states of the visual system as varying in accordance with distance, much as his geometrical compasses vary their spatial relations in accordance with geometrical proportions. This reading challenges the notion that a two-dimensional sensation (without three-dimensional phenomenality) was universally accepted prior to the nineteenth century by positing a direct psychophysiological account of the experience of distance in Descartes. It thereby challenges the interpretations of Descartes on natural geometry of George Berkeley, Nancy Maull, Margaret Wilson, Erwin Panofsky, and Jonathan Crary. (shrink)

Many of Margaret Cavendish’s criticisms of Thomas Hobbes in the Philosophical Letters (1664) relate to the disorder and damage that she holds would result if Hobbesian pressure were the cause of visual perception. In this paper, I argue that her “two men” thought experiment in Letter IV is aimed at a different goal: to show the explanatory potency of her account. First, I connect Cavendish’s view of visual perception as “patterning” to the “two men” thought experiment in Letter IV. Second, (...) I provide a potential reply on Hobbes’s behalf that appeals to physiological differences between perceivers’ sense organs, drawing upon Hobbes’s optics in De homine. Third, I argue that such a reply would misunderstand Cavendish’s objective of showing the limited explanatory resources available in understanding visual perception as pressing when compared to her view of visual perception as patterning. (shrink)

Where are we to look for the unique hues? Out in the world? In the eye? In more central processing? 1. There are difficulties looking for the structure of the unique hues in simple combinations of cone-response functions like ( L − M ) and ( S − ( L + M )): such functions may fit pretty well the early physiological processing, but they don’t correspond to the structure of unique hues. It may seem more promising to look (...) to, e.g., Hurvich & Jameson’s ‘chromatic response functions’; but these report on psychophysical behaviour, not on underlying physiology. So ‘opponent processing’ isn’t any particular help on the unique hues—and even physiology in general seems not to have come up with any good correlate or explanation. 2. Wright ( Review of Philosophy and Psychology 2: 1–17, 2011 ) looks in a different place: to (a) magnitude of total visual response that a stimulus light provokes, the maxima and minima of which, he thinks, give us the boundaries of the main hue categories (Wright connects these with Thornton’s ‘prime’ and ‘antiprime’ colours in an illuminant: Journal of the Optical Society of America 61 ( 1971 ): 1155–1163); and (b) the ratio of chromatic to achromatic response, the maxima and minima of which, he suggests, give us the focal points of the unique hues. The suggestions are extremely interesting; but the desired correspondences have some counterexamples; and where they hold, one could wonder how much they depend upon the particular choice of functions to measure (a) and (b); and one could hope for more of an explanatory linkage between the sets of items in question. 3. Could the unique hues come from, so to speak, the external world? White and black can easily be defined as particular kinds of reflectance. What of the standard four unique hues? Variation in kinds of sunlight and skylight coincides well with variation along a line from unique yellow to unique blue (cf. Shepard 1992 , Mollon 2006 ). If we wanted something to calibrate our standards for unique yellow and blue as the lens of the eye changes with age, and despite interpersonal cone differences, this would be a good basis—and there are several ways this can be extended to surface colours. But is there any essential connection between these things: is there any rationale why the light of the sun and the sky should be counted as unique hued ? An answer may be: because in our environment, these illuminants are as close to white (or the natural illuminant colour) as you can get—to see things tinged with sunlight or skylight should be to see them minimally tinged with any alien colour. Whereas other hues in an illuminant would be treated as tinging with a more alien colour the thing seen. (shrink)

Second harmonic generating (SHG) nanoprobes have recently emerged as versatile and durable labels suitable for in vivo imaging, circumventing many of the inherent drawbacks encountered with classical fluorescent probes. Since their nanocrystalline structure lacks a central point of symmetry, they are capable of generating second harmonic signal under intense illumination – converting two photons into one photon of half the incident wavelength – and can be detected by conventional two‐photon microscopy. Because the optical signal of SHG nanoprobes is based on (...) scattering, rather than absorption as in the case of fluorescent probes, they neither bleach nor blink, and the signal does not saturate with increasing illumination intensity. When SHG nanoprobes are used to image live tissue, the SHG signal can be detected with little background signal, and they are physiologically inert, showing excellent long‐term photostability. Because of their photophysical properties, SHG nanoprobes provide unique advantages for molecular imaging of living cells and tissues with unmatched sensitivity and temporal resolution. (shrink)

Philosophy: its relation to life and education.--The ideslism of Spinoza.--Recent discussion in materialism.--Professor Watson on reality and time.--The cosmic and the moral.--Psychology past and present.--The postulates of physiological psychology.--The origin of volition in childhood.--Imitation: a chapter in the natural history of consciousness.--The origin of emotional expression.--The perception of external reality.--Feeling, belief, and judgment.--Memory for square size.--The effect of size-contrast upon judgments of position in the retinal field.--An optical illusion.--New questions in mental chronometry. Types of reaction.--The "type-theory" of reaction.--The psychology (...) of religion.--Shorter philosophical papers.--Shorter literary papers. (shrink)

Originally published in 1991. Philoponus’ long commentary on Aristotle’s definition of light sets up the major concerns, both in optics and theory of light, that is discussed here. Light was of special interest in Neoplatonism because of its being something incorporeal in the world of natural bodies and therefore had a special role in the philosophical analysis of the interpenetration of bodies and also as a paradigm for the soul-body problem. The material investigated in this book contains much about (...) the physiology of vision as well as the propagation of light. Several chapters investigate the philosophical theory and its origins in ‘multiplication of species.’ These issues in the history of science philosophy are looked at further and an analysis is offered of the development of the distinction between Aristotle’s kinesis and energeia. The book covers a substantial amount of the philosophy of mathematical science from the point of view of Philoponus, drawing on more of his works relating to three dimensionality. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:HUME'S IDEAS In the eighteenth century, there was widespread acceptance of a physiological basis for cognition. Some writers even argued for a rather detailed correlation between awareness and physiological changes, suggesting that (a) the former could be adequately explained in terms of the latter or, in some few instances, (b) that the former are the latter. David Hartley may come to mind as fitting one or the (...) other of these alternatives, but Robert Hooke had earlier argued for ideas as brain impressions, as of course did Descartes in his early scientific treatises. There was also one medical doctor in the eighteenth century, Dr. Astruc, who seems (on the basis of what Chambers reports) to have attempted a very specific correlation between specific forms of awareness and specific states and changes in physiology. There were also writers in this century who warned against the dangers of using physical-object vocabulary when talking about the mind and acts of awareness. Berkeley is one such writer,- Thomas Reid at the end of the century traced, to the use of this vocabulary, what he took to be the indirect realism of the way of ideas. Hume is writing in both these traditions: the tradition of using physical language for characterizing mental operations and the tradition of physiological explanations and correlations. The phrase used by Alexander Pope and Hume, 'the anatomy of the mind', seems to be a mixed metaphor, but it is a phrase which I take as an indication that Hume is doing what we would call 'cognitive psychology'. Another phrase used by Hume (this time in the Enquiry), 'mental geography', may capture his enterprise better: 'geography' still sounds physical, but it is modified by 'mental'. Hume is engaged in mental mapping. I want to take a look at the use of the term 'idea' in Hume's writing (mainly in the Treatise) in order to see 2. whether Hume's text enables us to say anything about the nature of his ideas, to discover what role they play in his mental geography. As far as I can determine, there are three possible candidates for the nature of ideas in Hume: images, brain impressions, and cognitive contents. The first of these is, I think, the standard reading of Hume's ideas. Professor Anderson has presented strong argument and evidence to support the second. I will be suggesting that the third is the best candidate, given the full range of the text of the Treatise. Of course, the correct answer 4 may be all three of these. The Treatise opens by dividing all perceptions of the human mind into two kinds. Impressions and ideas differ in the degree of force and liveliness with which they strike upon the mind. Even though the language of 'force' and 'liveliness' may be borrowed from physical talk, it is the mind, not the brain, on which perceptions strike. The examples of impressions are sensations, passions, and emotions. Ideas are said to be the faint images of these impressions in thinking and reasoning. The term 'image' throughout the eighteenth century never receives any clear explication. Its inheritance from optical treatises always hangs about it. We should look to the examples cited by Hume, in order to see whether we can construct a meaning for that term when used in these psychological contexts. Let us look first at his very first example of 'ideas': all the perceptions excited by the present discourse. (Tl) He explicitly excludes from these perceptions those which arise from the sight and touch, as well as the immediate pleasure or uneasiness his discourse may excite in us. The perceptions which are thus excluded are sensations and emotions, the impressions he has just distinguished. The only candidate left for ideas would seem to be what this discourse says, our thoughts about it, my understanding of what it says. The distinction is not one Hume thinks is difficult to follow: Every one of himself will readily perceive the difference betwixt feeling and thinking. (Tl-2) Last week I was sad, today I recall that feeling of sadness/ the difference between being sad and remembering that I was sad. Hume gives a different example: the perceptions formed when... (shrink)

The highly ordered neuronal projections from the retina to the tectum mesencephali (optic tectum) in several vertebrate groups have been intensively studied. Several hypotheses so far have been proposed, suggesting mechanisms to explain the topographical and biochemical specificity of the retinotectal projections during ontogeny. In the present paper we compare the main hypotheses of retinotectal development with respect to the nature of specificity envisaged, the activity-dependence versus inheritance criterium and the strategy of argument, in casu the descriptive versus interferential type (...) of argument. Matching of the current developmental hypotheses and mechanisms for elimination or persistance of contralateral, respectively ipsilateral connections, is attempted with respect to the known neuroanatomical connectivity data in the amphibian optic tectum and with respect to the symmetry relations between ipsilateral and contralateral connection patterns described in amphibians and other vertebrate groups. Local mechanisms influencing the survival potential of synaptic contacts between retinal afferents and tectal neurons are probably essential for generating global symmetry patterns. Finally, a global topological approach is discussed with respect to its applicability in the amphibian retinotectal projection system. Basic assumptions of topological modeling appear to rely on anatomical and functional properties of the visual system like left-right symmetry, dichotomy, (absence of) convergence and segregation of fibers and neurons into columnar information units. It is concluded however, that more neuroanatomical, physiological and ultrastructural data are needed to establish a formalized operation model of the amphibian retinotectal system. (shrink)

Different explanations of color vision favor different philosophical positions: Computational vision is more compatible with objectivism (the color is in the object), psychophysics and neurophysiology with subjectivism (the color is in the head). Comparative research suggests that an explanation of color must be both experientialist (unlike objectivism) and ecological (unlike subjectivism). Computational vision's emphasis on optimally prespecified features of the environment (i.e., distal properties, independent of the sensory-motor capacities of the animal) is unsatisfactory. Conceiving of visual perception instead as the (...) visual guidance of activity in an environment that is determined largely by that very activity suggests new directions for research. (shrink)

According to Thomas Reid, the development of natural sciences following the model of Newton's Principia and Optics would provide further evidence for the belief in a provident God. This project was still supported by his student, Dugald Stewart, in the early nineteenth century. John Fearn , an early critic of the Scottish common sense school, thought that the rise of ‘infidelity’ in the wake of scientific progress had shown that the apologetic project of Reid and Stewart had failed. In (...) reaction to Reid and Stewart, he proposed an idealist philosophy that would dispense with the existence of matter, and would thus cut at the root what he thought was the main source of modern atheism. In this paper, I consider Fearn's critique of Reid and Stewart in his main works: First Lines of the Human Mind and Manual of the Physiology of Mind . I also consider Fearn's arguments against Hume and in favour of a renewed apologetics in An Essay on the Philosophy of Faith and the Economy of Revelatio.. (shrink)

Hermann von Helmholtz was a leading figure of nineteenth-century European intellectual life, remarkable even among the many scientists of the period for the range and depth of his interests. A pioneer of physiology and physics, he was also deeply concerned with the implications of science for philosophy and culture. From the 1850s to the 1890s, Helmholtz delivered more than two dozen popular lectures, seeking to educate the public and to enlighten the leaders of European society and governments about the potential (...) benefits of science and technology to a developing modern society. David Cahan has selected fifteen of these lectures, which reflect the wide range of topics of crucial importance to Helmholtz and his audiences. Among the subjects discussed are the origins of the planetary system, the relation of natural science to science in general, the aims and progress of the physical sciences, the problems of perception, and academic freedom in German universities. This collection also includes Helmholtz's fascinating lectures on the relation of optics to painting and the physiological causes of harmony in music, which provide insight into the relations between science and aesthetics. Science and Culture makes available again Helmholtz's eloquent arguments on the usefulness, benefits, and, intellectual pleasures of understanding the natural world. With Cahan's Introduction to set these essays in their broader context, this collection makes an important contribution to the philosophical and intellectual history of Europe at a time when science played an increasingly significant role in social, economic, and cultural life. (shrink)

Psychologues et philosophes partagent une même lecture de l'histoire de la psychologie selon laquelle le recours aux mathématiques pour constituer une psychométrie au XIX e siècle aurait été l'indice évident d'une séparation définitive entre psychologies scientifique et philosophique. Le présent article montre que le projet d'une psychométrie est nettement plus ancien et qu'il est au contraire né dans un espace des savoirs dans lequel métaphysique, mathématique, optique et physiologie n'étaient pas séparés. Both psychologists and philosophers share a very same reading (...) of the history of psychology according to which the recourse to mathematics in order to build psychometrics in the 19th century were to have been the obvious indication of an outmost separation between scientific and philosophical psychologies. This paper shows that the project of a psychometrics is far older, born as it was in an environment of knowledge in which metaphysics, mathematics, optics and physiology were not separated. (shrink)

Insect and crustacean lineages diverged over 500 Myr ago, and there are continuing uncertaintles about whether they evolved from a common arthropod ancestor or, alternatively, they evolved independently from annelid worms. Despite the diversity of their limbs and lifestyles, the nervous systems of insects and crustaeeans share many common features both in development and in function. Cellular and molecular embryology techniques reveal good evidence for homologies in the developing segmental ganglia. In the visual system, this seemingly common programme of insect (...) and crustacean CNS development culminates in common adult neural function. Comparisons of the cellular anatomy and physiology of animals as diverse as flies and crayfishes indicate that the neural circuits in the lamina of their optic lobe have been inherited largely unchanged from a common ancestor with good compound eyes. (shrink)

Background Speech understanding may rely not only on auditory, but also on visual information. Non-invasive functional neuroimaging techniques can expose the neural processes underlying the integration of multisensory processes required for speech understanding in humans. Nevertheless, noise (from fMRI) limits the usefulness in auditory experiments, and electromagnetic artefacts caused by electronic implants worn by subjects can severely distort the scans (EEG, fMRI). Therefore, we assessed audio-visual activation of temporal cortex with a silent, optical neuroimaging technique: functional near-infrared spectroscopy (fNIRS). Methods (...) We studied temporal cortical activation as represented by concentration changes of oxy- and deoxy-hemoglobin in four, easy-to-apply fNIRS optical channels of 33 normal-hearing adult subjects and 5 post-lingually deaf cochlear implant (CI) users in response to supra-threshold unisensory auditory and visual, as well as to congruent auditory-visual speech stimuli. Results Activation effects were not visible from single fNIRS channels. However, by discounting physiological noise through reference channel subtraction, auditory, visual and audiovisual speech stimuli evoked concentration changes for all sensory modalities in both cohorts (p<0.001). Auditory stimulation evoked larger concentration changes than visual stimuli (p<0.001). A saturation effect was observed for the audiovisual condition. Conclusions Physiological, systemic noise can be removed from fNIRS signals by reference channel subtraction. The observed multisensory enhancement of an auditory cortical channel can be plausibly described by a simple addition of the auditory and visual signals with saturation. (shrink)

Descartes was born in La Haye (now Descartes) in Touraine and educated at the Jesuit college of La Fleche` in Anjou. Descartes’modern reputation as a rationalistic armchair philosopher, whose mind–body dualism is the source of damaging divisions between psychology and the life sciences, is almost entirely undeserved. Some 90% of his surviving correspondence is on mathematics and scientific matters, from acoustics and hydrostatics to chemistry and the practical problems of constructing scientific instruments. Descartes was just as interested in the motions (...) of matter as in the supernatural soul, and he advised against spending too much time on metaphysical inquiries which neglect imagination and the senses. After meeting the Dutch engineer Isaac Beeckman in 1618, Descartes became committed to a systematically ‘mechanical’account of nature. This involved explaining all natural processes in terms of interactions between microscopic material bodies in motion. Descartes modelled his physics and cosmology on the behaviour of fluids, which also have a distinctive and central role in his physiology: the key processes for natural philosophical investigation are the circulation and mutual displacement of constrained bodies, rather than the isolated collisions of atoms in a void. Descartes settled in Holland in 1628, and commenced an ambitious programme of physiological research. In 1630 he was ‘studying chemistry and anatomy simultaneously’, and in late 1632 he was ‘dissecting the heads of various animals’, in order to ‘explain what imagination, memory, etc. consist in’. By late 1633 Descartes had almost completed L’homme, the Treatise on Man; but he abandoned plans to publish it along with a work on matter theory and optics which relied on Copernican cosmology, after he heard of the condemnation of Galileo. L’homme was published posthumously in 1662 (Latin) and 1664 (French); not until 1972 was it fully translated into English. L’homme draws on many (mostly unnamed) Renaissance medical writers, and covers, firstly, a range of traditional physiological topics, such as digestion and respiration.. (shrink)

Descartes' The World offers the most comprehensive vision of the nature of the world since Aristotle, and is crucial for an understanding of his later writings, in particular the Meditations and Principles of Philosophy. Above all, it provides an insight into how Descartes conceived of natural philosophy before he started to reformulate his doctrines in terms of a sceptically driven epistemology. Of its two parts, the Treatise on Light introduced the first comprehensive, quantitative version of a mechanistic natural philosophy, supplying (...) a theory of matter, a physical optics, and a cosmology. The Treatise on Man provided the first comprehensive mechanist physiology. This volume also includes translations of material important for an understanding of the work: related sections from the Dioptrics and the Meteors, and an English translation of the complete text of The Description of the Human Body. (shrink)

The laser scanning confocal microscope (LSCM)LSCM: laser scanning confocal microscope; FISH: fluorescence in situ hybridisation; DiO6: 3,3′‐dihexyloxacarbocyanine iodide; NBD‐ceramide: 6‐((N‐(7‐nitrobenz‐2‐oxa‐1,3‐diazol‐4‐yl)amino)‐caproyl)sphingosine; DiO: 3,3′‐dioctadecyloxacarbocyanine perchlorate; DiI: 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethyl‐indocarbocyanine perchlorate; CCD: charge‐coupled device; DIC: differential interference contrast; FURA2: (‐(2‐(5‐carboxyoxazol‐2‐yl)‐6‐aminobenzofuran‐5‐oxy)‐2‐)2′‐amino‐5′‐methylphenoxy)‐ethane‐N,N,N′,N′‐ tetraacetic acid, sodium salt);BCECF: 2′,7′‐bis‐(carboxyethyl)‐5‐(and‐6‐)‐carboxyfluorescein;fluo‐3: 1‐(2‐amino‐5‐(2,7‐dichloro‐6‐hydroxy‐3‐oxo‐3H‐xanthen‐9‐yl)‐2‐(2′amino‐5′‐methylphenoxy)‐ethane‐N,N, N′,N′,‐tetraacetic acid, ammonium salt; DAPI: 4′,6‐diamidino‐2‐phenylindole, dihydrochloride; PET: positron emission tomogrophy; CT: computer‐assisted tomogrophy; CiD: cubitus interruptus dominus; MRC: Medical Research Council; TOTO‐1: benzothiazolium‐4‐quinolinium dimer; YOYO‐1: benzoxazolium‐4‐quinolinium dimer; ex.: excitation wavelength; em.: emission wavelength. is now established as an invaluable tool in (...) developmental biology for improved light microscope imaging of fluorescently labelled eggs, embryos and developing tissues. The universal application of the LSCM in biomedical research has stimulated improvements to the microscopes themselves and the synthesis of novel probes for imaging biological structures and physiological processes. Moreover the ability of the LSCM to produce an optical series in perfect register has made computer 3‐D reconstruction and analysis of light microscope images a practical option. (shrink)

The influence of light on the lives of living organisms is all-pervasive, affecting movement, vision, behavior, and physiological activity. This book is a biophysically grounded comparative survey of how animals detect light and perceive their surroundings. Included are discussions of photoreceptors, light emitters, and eyes. The book focuses in particular on the kinds of optical systems that have evolved, beginning with unicellular organisms that detect and respond to light through to more advanced and complex designs for imaging. The relevance (...) of these studies extends beyond biology, since these findings can be used to help develop photoreceptor energy conversion and information systems, and optical imaging devices with a wide range of everyday applications. The book will appeal to biophysicists, photobiologists, bioengineers, neuroscientists, and all researchers working in the area of vision and visual optics. (shrink)

In Amerindian ontologies, hallucinations or visions, rather than being dismissed as delusions or symbolic constructs, are recognized as means of perceptual access to physical reality. Lowland South American shamans claim to be able to diagnose and treat infectious diseases, and to assess the status of wildlife resources through interactions with pathogenic agents perceived in visions. This essay examines some perceptual capabilities that shamans might be employing to explore their physical reality. The structure of the eye affords a form of microscopy (...) of retinal structures and of objects flowing within them, including cells and microbial agents during systemic infection. Lowland South American shamanic practices involve optical and physiological conditions that optimize entoptic microscopy. Images of those visions display the characteristic features of shadow formation, confirming their microscopic origin. This phenomenological access to the microscopic world and similarities with the panorama depicted by current microbiology indicate the commensurability of these forms of knowledge. (shrink)

The medium surrounding cells either in culture or in tissues contains a chemical mix varying with cell state. As solutes move in and out of the cytoplasmic compartment they set up characteristic signatures in the cellular boundary layers. These layers are complex physical and chemical environments the profiles of which reflect cell physiology and provide conduits for intercellular messaging. Here we review some of the most relevant characteristics of the extracellular/intercellular space. Our initial focus is primarily on cultured cells but (...) we extend our consideration to the far more complex environment of tissues, and discuss how chemical signatures in the boundary layer can or may affect cell function. Critical to the entire essay are the methods used, or being developed, to monitor chemical profiles in the boundary layers. We review recent developments in ultramicro electrochemical sensors and tailored optical reporters suitable for the task in hand. (shrink)

There are two standing, incompatible accounts of Descartes’ contributions to the study of psychosomatic phenomena that pervade histories of medicine, psychology, and psychiatry. The first views Descartes as the father of “rational psychology” a tradition that defines the soul as a thinking, unextended substance. The second account views Descartes as the father of materialism and the machine metaphor. The consensus is that Descartes’ studies of optics and motor reflexes and his conception of the body-machine metaphor made early and important (...) contributions to physiology and neuroscience but otherwise his impact was minimal. These predominately negative assessments of Descartes’ contributions give a false impression of the role his philosophy played in the development of medicine and psychiatry in seventeenth-century France and beyond. I explore Descartes’ influence in the little-known writings of a doctor from Toulouse, and . A study of Bayle gives us occasion to rethink the nature and role of psychosomatic explanation in Descartes’ philosophy. The portrait I present is of a Cartesian science that had an actual and lasting effect on medical science and practice, and may offer something of value to practitioners today. (shrink)

The glowing light of cinema, which continues to claim supremacy as a collective site for evolving senses of time, has fundamentally changed since its inception, from exclusively projected light to primarily emitted light. Digital, rather than analog projectors, dominate in personal rather than public spheres. The physiological and behavioral effects of those technologies manipulate our biological clocks, creating an entanglement of time-sensing. Similarly, the art of cinema now relies far more upon energy-intensive materials and methods, from equipment to image (...) manufacturing and data flow. This essay takes the twelve-hour clock as a slanted optic to address those profound shifts, choosing a handful of moving-image artists to feature, including Deborah Stratman, Nikolaus Geyrhalter, and Mikael Kristersson, who are attempting to find alternative temporal modes of depicting the hyperobjectiveness of eternity, ecocrises, dystopias, and deep time on screen. (shrink)

It seems to be self-evident that through perception we gain access to the material world. That visual perception takes an important role seems self-evident as well. But what exactly do we see? The objects themselves or just their perceptible properties? How do we manage to see something at all? Are we capable of seeing solely through optical and physiological processes or does viewing something asks for presupposed terms in order to help us to see something as something? These questions, (...) currently discussed at great length within the framework of cognitive and epistemological theory, were already cause for intensive debate in the early modern times. In many aspects, those discussions in the 17th and 18th century laid the groundwork for today’s theories: on one hand, they identified the problems with great clarity and on the other, they provided strategies for possible solutions which are still of value today. This volume will provide new access to those debates (from Descartes to Reid) and will present these debates to an audience interested in philosophical questions. The book shows that the early modern times is not just a respectable museum in the history of philosophy, but on the contrary, a very productive and stimulating philosophical epoch which invites further discussion. (shrink)

It seems to be self-evident that through perception we gain access to the material world. That visual perception takes an important role seems self-evident as well. But what exactly do we see? The objects themselves or just their perceptible properties? How do we manage to see something at all? Are we capable of seeing solely through optical and physiological processes or does viewing something asks for presupposed terms in order to help us to see something as something? These questions, (...) currently discussed at great length within the framework of cognitive and epistemological theory, were already cause for intensive debate in the early modern times. In many aspects, those discussions in the 17th and 18th century laid the groundwork for today’s theories: on one hand, they identified the problems with great clarity and on the other, they provided strategies for possible solutions which are still of value today. This volume will provide new access to those debates (from Descartes to Reid) and will present these debates to an audience interested in philosophical questions. The book shows that the early modern times is not just a respectable museum in the history of philosophy, but on the contrary, a very productive and stimulating philosophical epoch which invites further discussion. (shrink)

Luminescence‐based sensing schemes for oxygen have experienced a fast growth and are in the process of replacing the Clark electrode in many fields. Unlike electrodes, sensing is not limited to point measurements via fiber optic microsensors, but includes additional features such as planar sensing, imaging, and intracellular assays using nanosized sensor particles. In this essay, I review and discuss the essentials of (i) common solid‐state sensor approaches based on the use of luminescent indicator dyes and host polymers; (ii) fiber optic (...) and planar sensing schemes; (iii) nanoparticle‐based intracellular sensing; and (iv) common spectroscopies. Optical sensors are also capable of multiple simultaneous sensing (such as O2 and temperature). Sensors for O2 are produced nowadays in large quantities in industry. Fields of application include sensing of O2 in plant and animal physiology, in clinical chemistry, in marine sciences, in the chemical industry and in process biotechnology. (shrink)

As driving functions become increasingly automated, motorists run the risk of becoming cognitively removed from the driving process. Psychophysiological measures may provide added value not captured through behavioral or self-report measures alone. This paper provides a selective review of the psychophysiological measures that can be utilized to assess cognitive states in real-world driving environments. First, the importance of psychophysiological measures within the context of traffic safety is discussed. Next, the most commonly used physiology-based indices of cognitive states are considered as (...) potential candidates relevant for driving research. These include: electroencephalography and event-related potentials, optical imaging, heart rate and heart rate variability, blood pressure, skin conductance, electromyography, thermal imaging, and pupillometry. For each of these measures, an overview is provided, followed by a discussion of the methods for measuring it in a driving context. Drawing from recent empirical driving and psychophysiology research, the relative strengths and limitations of each measure are discussed to highlight each measures’ unique value. Challenges and recommendations for valid and reliable quantification from lab to (less predictable) real-world driving settings are considered. Finally, we discuss measures that may be better candidates for a near real-time assessment of motorists’ cognitive states that can be utilized in applied settings outside the lab. This review synthesizes the literature on in-vehicle psychophysiological measures to advance the development of effective human-machine driving interfaces and driver support systems. (shrink)

According to Kepler and Descartes, the geometry of the triangle formed by the two eyes when focused on a single point affords perception of the distance to that point. Kepler characterized the processes involved as associative learning. Descartes described the processes as a “ natural geometry.” Many interpreters have Descartes holding that perceivers calculate the distance to the focal point using angle-side-angle, calculations that are reduced to unnoticed mental habits in adult vision. This article offers a purely psychophysiological interpretation of (...) Descartes’s natural geometry. In his account of perceived limb position from the Treatise on Man, he envisioned a central brain state that controls ocular convergence and thereby co-varies with the distance from observer to object. A psychophysiological law relates the visual perception of distance to this brain state. Descartes also invokes more traditional theories of distance and size perception based on unnoticed judgments, yielding a hybrid account. (shrink)