Two traditions have had a great impact on the theoretical and experimental research of perception. One tradition is statistical, stretching from Fechner's enunciation of psychophysics in 1860 to the modern view of perception as statistical decision making. The other tradition is phenomenological, from Brentano's “empirical standpoint” of 1874 to the Gestalt movement and the modern work on perceptual organization. Each tradition has at its core a distinctive assumption about the indivisible constituents of perception: the just-noticeable differences of sensation in the (...) tradition of Fechner vs. the phenomenological Gestalts in the tradition of Brentano. But some key results from the two traditions can be explained and connected using an approach that is neither statistical nor phenomenological. This approach rests on a basic property of any information exchange: a principle of measurement formulated in 1946 by Gabor as a part of his quantal theory of information. Here the indivisible components are units (quanta) of information that remain invariant under changes of precision of measurement. This approach helped to understand how sensory measurements are implemented by single neural cells. But recent analyses suggest that this approach has the power to explain larger-scale characteristics of sensory systems. (shrink)

In the foundations of Fechner's psychophysics, the concept of “functional relation” plays a highly relevant role in three different respects: (1) in respect to the principles of measurement, (2) in respect to the mind-body problem, and (3) in respect to the concept of a law of nature. In all three cases, it is important to explain the difference between a functional dependency of a variable upon another and a causal relationship between two (or more) variables. In all three respects, Ernst (...) Mach developed Fechner's ideas further and tried to extend the lessons he had learned from using the concept of a functional relation in psychophysics to the whole of science. For all three cases, I explain why they are still relevant for psychophysics and philosophy today. (shrink)

A. J. Ayer’s Language, Truth, and Logic had been responsible for introducing the Vienna Circle’s ideas, developed within a Germanophone framework, to an Anglophone readership. Inevitably, this migration from one context to another resulted in the alteration of some of the concepts being transmitted. Such alterations have served to facilitate a number of false impressions of Logical Empiricism from which recent scholarship still tries to recover. In this paper, I will attempt to point to the ways in which LTL has (...) helped to foster the various mistaken stereotypes about Logical Empiricism which were combined into the received view. I will begin by examining Ayer’s all too brief presentation of an Anglocentric lineage for his ideas. This lineage, as we shall see, simply omits the major 19th century Germanophone influences on the rise of analytic philosophy. The Germanophone ideas he presents are selectively introduced into an Anglophone context, and directed towards various concerns that arose within that context. I will focus on the differences between Carnap’s version of the overcoming of metaphysics, and Ayer’s reconfiguration into what he calls the elimination of metaphysics. Having discussed the above, I will very briefly outline the consequences that Ayer’s radicalisation of the Vienna Circle’s doctrines had on the subsequent Anglophone reception of Logical Empiricism. (shrink)

This paper has the aim of making Johannes von Kries’s masterpiece, Die Principien der Wahrscheinlichkeitsrechnung of 1886, a little more accessible to the modern reader in three modest ways: first, it discusses the historical background to the book ; next, it summarizes the basic elements of von Kries’s approach ; and finally, it examines the so-called “principle of cogent reason” with which von Kries’s name is often identified in the English literature.

Neutral monism is the view that both ‘mind’ and ‘matter’ are grounded in a more fundamental form of reality that is intrinsically neither mental nor material. It has often been treated as an odd fringe theory deserving of at most a footnote in the broader philosophical debates. Yet such attitudes do a grave disservice to its sophistications and significance for late nineteenth and early twentieth-century philosophy of mind and psychology. This paper sheds light on this neglected view by situating it (...) within broader historical monist debates about the mind and bringing attention to one of its central internal disputes regarding ‘mental chemistry’. By taking a closer look at how Ernst Mach, William James, and Bertrand Russell address the question of whether and how our mental episodes are composed of more basic elements, it highlights deep differences among their conceptions of the fundamental ‘neutral stuff’ and its relations to ‘mind’ and ‘matter’. (shrink)

An overview of the German philosophy of science community is given for the years 1992–2012, based on a survey in which 159 philosophers of science in Germany participated. To this end, the institutional background of the German philosophy of science community is examined in terms of journals, centers, and associations. Furthermore, a qualitative description and a quantitative analysis of our survey results are presented. Quantitative estimates are given for: (a) academic positions, (b) research foci, (c) philosophers’ of science most important (...) publications, and (d) externally funded projects, where for (c) all survey participants had indicated their five most important publications in philosophy of science. In addition, the survey results for (a)–(c) are also qualitatively described, as they are interesting in their own right. With respect to (a), we estimated the gender distribution among academic positions. Concerning (c), we quantified philosophers’ of science preference for (i) journals and publishers, (ii) publication format, (iii) language, and (iv) coauthorship for their most important publications. With regard to research projects, we determined their (i) prevalence, (ii) length, and (iii) trend (an increase in number?) as well as their most frequent (iv) research foci and (v) funding organizations. We also distinguished between German-based and non-German-based journals, publishers, and funding institutions, making it thereby possible to evaluate the involvement of the German philosophy of science community in the international research landscape. Finally, we discuss some implications of our findings. (shrink)

Sewall Wright first encountered the complex systems characteristic of gene combinations while a graduate student at Harvard's Bussey Institute from 1912 to 1915. In Mendelian breeding experiments, Wright observed a hierarchical dependence of the organism's phenotype on dynamic networks of genetic interaction and organization. An animal's physical traits, and thus its autonomy from surrounding environmental constraints, depended greatly on how genes behaved in certain combinations. Wright recognized that while genes are the material determinants of the animal phenotype, operating with great (...) regularity, the special nature of genetic systems contributes to the animal phenotype a degree of spontaneity and novelty, creating unpredictable trait variations by virtue of gene interactions. As a result of his experimentation, as well as his keen interest in the philosophical literature of his day, Wright was inspired to see genetic systems as conscious, living organisms in their own right. Moreover, he decided that since genetic systems maintain ordered stability and cause unpredictable novelty in their organic wholes (the animal phenotype), it would be necessary for biologists to integrate techniques for studying causally ordered phenomena (experimental method) and chance phenomena (correlation method). From 1914 to 1921 Wright developed his "method of path coefficient" (or "path analysis"), a new procedure drawing from both laboratory experimentation and statistical correlation in order to analyze the relative influence of specific genetic interactions on phenotype variation. In this paper I aim to show how Wright's philosophy for understanding complex genetic systems (panpsychic organicism) logically motivated his 1914-1921 design of path analysis. (shrink)

Sewall Wright first encountered the complex systems characteristic of gene combinations while a graduate student at Harvard's Bussey Institute from 1912 to 1915. In Mendelian breeding experiments, Wright observed a hierarchical dependence of the organism's phenotype on dynamic networks of genetic interaction and organization. An animal's physical traits, and thus its autonomy from surrounding environmental constraints, depended greatly on how genes behaved in certain combinations. Wright recognized that while genes are the material determinants of the animal phenotype, operating with great (...) regularity, the special nature of genetic systems contributes to the animal phenotype a degree of spontaneity and novelty, creating unpredictable trait variations by virtue of gene interactions. As a result of his experimentation, as well as his keen interest in the philosophical literature of his day, Wright was inspired to see genetic systems as conscious, living organisms in their own right. Moreover, he decided that since genetic systems maintain ordered stability and cause unpredictable novelty in their organic wholes, it would be necessary for biologists to integrate techniques for studying causally ordered phenomena and chance phenomena. From 1914 to 1921 Wright developed his "method of path coefficient", a new procedure drawing from both laboratory experimentation and statistical correlation in order to analyze the relative influence of specific genetic interactions on phenotype variation. In this paper I aim to show how Wright's philosophy for understanding complex genetic systems logically motivated his 1914-1921 design of path analysis. (shrink)

The conservation of energy and momentum have been viewed as undermining Cartesian mental causation since the 1690s. Modern discussions of the topic tend to use mid-nineteenth century physics, neglecting both locality and Noether’s theorem and its converse. The relevance of General Relativity has rarely been considered. But a few authors have proposed that the non-localizability of gravitational energy and consequent lack of physically meaningful local conservation laws answers the conservation objection to mental causation: conservation already fails in GR, so there (...) is nothing for minds to violate. This paper is motivated by two ideas. First, one might take seriously the fact that GR formally has an infinity of rigid symmetries of the action and hence, by Noether’s first theorem, an infinity of conserved energies-momenta. Second, Sean Carroll has asked how one should modify the Dirac–Maxwell–Einstein equations to describe mental causation. This paper uses the generalized Bianchi identities to show that General Relativity tends to exclude, not facilitate, such Cartesian mental causation. In the simplest case, Cartesian mental influence must be spatio-temporally constant, and hence 0. The difficulty may diminish for more complicated models. Its persuasiveness is also affected by larger world-view considerations. The new general relativistic objection provides some support for realism about gravitational energy-momentum in GR. Such realism also might help to answer an objection to theories of causation involving conserved quantities, because energies-momenta would be conserved even in GR. (shrink)

Misconceptions about energy conservation abound due to the gap between physics and secondary school chemistry. This paper surveys this difference and its relevance to the 1690s–2010s Leibnizian argument that mind-body interaction is impossible due to conservation laws. Justifications for energy conservation are partly empirical, such as Joule’s paddle wheel experiment, and partly theoretical, such as Lagrange’s statement in 1811 that energy is conserved if the potential energy does not depend on time. In 1918 Noether generalized results like Lagrange’s and proved (...) a converse: symmetries imply conservation laws and vice versa. Conservation holds if and only if nature is uniform. The rise of field physics during the 1860s–1920s implied that energy is located in particular places and conservation is primordially local: energy cannot disappear in Cambridge and reappear in Lincoln instantaneously or later; neither can it simply disappear in Cambridge or simply appear in Lincoln. A global conservation law can be inferred in some circumstances. Einstein’s General Relativity, which stimulated Noether’s work, is another source of difficulty for conservation laws. As is too rarely realized, the theory admits conserved quantities due to symmetries of the Lagrangian, like other theories. Indeed General Relativity has more symmetries and hence more conserved energies. An argument akin to Leibniz’s finally gets some force. While the mathematics is too advanced for secondary school, the ideas that conservation is tied to uniformities of nature and that energy is in particular places, are accessible. Improved science teaching would serve the truth and enhance the social credibility of science. (shrink)

Marburg Neo-Kantianism has attracted substantial interest among contemporary philosophers drawn by its founding idea that the success of advanced theoretical science is a given fact and it is the task of philosophical inquiry to ground the objectivity of scientific achievement in its a priori sources (Cohen and Natorp 1906, p. i). The Marburg thinkers realized that recent advances and developments in the mathematical sciences had changed the character of Kant’s transcendental project, demanding new methods and approaches to establish the objectivity (...) of the latest insights into physical reality. Hermann Cohen, one of the founders of the Marburg School, attempted to base the objectivity of science on the concepts of .. (shrink)

The aim of this paper is to develop a pluralist interpretation of the phenomenal concept strategy (PCS). My starting point is Horgan and Tienson's deconstructive argument according to which proponents of PCS face the following dilemma: either phenomenal concepts or physical concepts allow us to conceive phenomenal states as they are in themselves. If phenomenal concepts allow us to conceive phenomenal states as they are in themselves, then phenomenal states are non-physical states and physicalism is wrong. If physical concepts allow (...) us to conceive phenomenal states as they are in themselves, then phenomenal concepts are derivative and PCS is wrong. While Horgan and Tienson assume that their argument shows that PCS leads to dualism, I argue that one can also adopt an ‘epistemic pluralism’ that rejects the idea of only one fundamental way of conceiving phenomenal states as they are in themselves. However, I also argue that epistemic pluralism eventually leads to a position that is compatible neither with dualism nor physicalism. Instead of justifying a non-reductive ‘new wave materialism’, PCS may therefore lead to a ‘new wave pluralism’ that is at odds with all mainstream positions in philosophy of mind. (shrink)

In economics, thought experiments are frequently justified by the difficulty of conducting controlled experiments. They serve several functions, such as establishing causal facts, isolating tendencies, and allowing inferences from models to reality. In this paper, I argue that thought experiments served a further function in economics: facilitating the quantitative definition and measurement of the theoretical concept of utility, thereby bridging the gap between theory and statistical data. I support my argument by a case study, the “hypothetical experiments” of the Norwegian (...) economist Ragnar Frisch (1895-1973). Frisch aimed to eliminate introspection and a subjective concept of utility from economic reasoning. At the same time, he sought behavioral foundations for economic theory that enabled quantitative reasoning. By using thought experiments to justify his set of choice axioms and facilitating the operationalization of utility, Frisch circumvented the problem of observing utility via actual experiments without eliminating the concept of utility from economic theory altogether. As such, these experiments helped Frisch to empirically support the theory’s most important results, such as the laws of demand and supply, without the input of new empirical findings. I suggest that Frisch’s experiments fulfill the main characteristics of thought experiments. (shrink)

This paper offers an introduction to Hermann Cohen’s Das Princip der Infinitesimal-Methode, and recounts the history of its controversial reception by Cohen’s early sympathizers, who would become the so-called ‘Marburg school’ of Neo-Kantianism, as well as the reactions it provoked outside this group. By dissecting the ambiguous attitudes of the best-known representatives of the school, as well as those of several minor figures, this paper shows that Das Princip der Infinitesimal-Methode is a unicum in the history of philosophy: it represents (...) a strange case of an unsuccessful book’s enduring influence. The “puzzle of Cohen’s Infinitesimalmethode,” as we will call it, can be solved by looking beyond the scholarly results of the book, and instead focusing on the style of philosophy it exemplified. Moreover, the paper shows that Cohen never supported, but instead explicitly opposed, the doctrine of the centrality of the ‘concept of function’, with which Marburg Neo-Kantianism is usually associated. (shrink)

Philosophy may relate to interdisciplinarity in two distinct ways On the one hand, philosophy may play an auxiliary role in the process of interdisciplinarity, typically through conceptual analysis, in the understanding that the disciplines themselves are the main epistemic players. This version of the relationship I characterise as ‘normal’ because it captures the more common pattern of the relationship, which in turn reflects an acceptance of the division of organized inquiry into disciplines. On the other hand, philosophy may be itself (...) the site for the production of interdisciplinary knowledge, understood as a kind of second-order understanding of reality that transcends the sort of knowledge that the disciplines provide, left to their own devices. This is my own position, which I dub ‘deviant’ and to which most of this article is devoted. I begin by relating the two types of interdisciplinarity to the organization of inquiry, especially their respective attitudes to the history of science. Underlying the two types are contrasting notions of what constitutes the ‘efficient’ pursuit of knowledge. This difference is further explored in terms of the organization of the university. The normal/deviant distinction was already marked in the institution’s medieval origins in terms of the difference between Doctors and Masters, respectively, an artefact of which remains in the postgraduate/undergraduate degree distinction. In the context of the history of the university, the prospects for deviant interdisciplinarity were greatest from the early sixteenth to the early nineteenth century—the period called ‘early modern’ in the philosophy curriculum. Towards the end of that period, due to Kant and the generation of idealists who followed him, philosophy was briefly the privileged site for deviant interdisciplinarity. After Hegel’s death, the mantle of deviant interdisciplinarity increasingly passed to some version of ‘biology’. I explore the ‘Natur-’ and ‘Geisteswissenschaft’ versions of that post-philosophical vision, which continue to co-exist within today’s biological science. I then briefly examine the chequered reputation of Jean-Baptiste Lamarck, someone who exemplified the promise and perils of deviant interdisciplinarity over the past 200 years. I conclude with an Epilogue that considers contemporary efforts to engage philosophy in interdisciplinary work, invoking William James as an exemplar. (shrink)

John Hughlings Jackson is a major figure at the origins of neurology and neuroscience in Britain. Alongside his contributions to clinical medicine, he left a large corpus of writing on localisation of function in the nervous system and other theoretical topics. In this paper I focus on Jackson’s “doctrine of concomitance”—his parallelist theory of the mind-brain relationship. I argue that the doctrine can be given both an ontological and a causal interpretation, and that the causal aspect of the doctrine is (...) especially significant for Jackson and his contemporaries. I interpret Jackson’s engagement with the metaphysics of mind as an instance of what I call meta-science—the deployment by scientists of metaphysical positions and arguments which help streamline empirical investigations by bracketing off unanswerable questions and focussing attention on matters amenable to the current tools of experimental research. (shrink)

RESUMO O artigo examina algumas influências teóricas de Freud para recuperar os valores epistemológicos que subjazem à composição de sua concepção de ciência da natureza. Se, por um lado, Freud teve acesso ao pensamento de autores específicos que participaram efetivamente dos caminhos percorridos pela psicologia em sua reivindicação de uma identidade científica, por meio de entrelaçamentos com a física e a fisiologia, por outro lado, ele também teve contato com certos filósofos que lhe permitiram uma aproximação a alguns defensores da (...) cientificidade da psicologia que não abandonam o naturalismo, nem recorrem ao solo fisiológico. Nossa avaliação histórica constituiu-se como uma defesa de que Freud sofreu diversas influências no tocante ao status da psicologia no campo das ciências da natureza. A pluralidade dessas influências evoca uma necessidade de abertura para a avaliação do modo pelo qual podemos colocar em perspectiva a epistemologia e a concepção do naturalismo de Freud. ABSTRACT This article examines some of the theoretical outlooks Freud used to acquire the epistemological values that underlie the foundation of his notion of natural science. On the one hand Freud was familiar with the ideas of specific authors, who had made major contributions that support of psychology's status as a science by appealing to physics and physiology. On the other hand, his contact with certain philosophers allowed him to use their defenses of psychology's scientific status without abandoning naturalism and without recourse to physiology. Our historical evaluation of these struggles supports that Freud was affected by various points of view concerning psychology's standing within the natural sciences. Owing to the diverse influences on Freud, we need to figure out how we can put his epistemology and his concept of naturalism into perspective. (shrink)

The article reevaluates the reception of Mendelism in France, and more generally considers the complex relationship between Mendelism and plant breeding in the first half on the 20th century. It shows on the one side that agricultural research and higher education institutions have played a key role in the development and institutionalization of genetics in France, whereas university biologists remained reluctant to accept this approach on heredity. But on the other side, plant breeders, and agricultural researchers, despite an interest in (...) Mendelism, never came to see it as the breeders' panacea, and regarded it instead as of only limited value for plant breeding. I account for this judgment in showing that the plant breeders and Mendelism designed two contrasting kinds of experimental systems and inhabited distinct experimental cultures. While Mendelian geneticists designed experimental systems that allowed the production of definite ratios of different forms that varied in relation to a few characters, plant breeders' experimental systems produced a wide range of variation, featuring combinations between hundreds of traits. Rather than breaking this multiple variation down into simple elements, breeders designed and monitored a genetic lottery. The gene was a unit in a Mendelian experimental culture, an "epistemic thing" as Rheinberger put it, that could be grasped by means of statistical regularities, but it remained of secondary importance for French plant breeders, for whom the strain or the variety -- not the gene -- was the fundamental unit of analysis and manipulation. (shrink)

Why did Bernhard Riemann, arguably the most original mathematician of his generation, spend the last year of life investigating the mechanism of hearing? Fighting tuberculosis and the hostility of eminent scientists such as Hermann Helmholtz, he appeared to forsake mathematics to prosecute a case close to his heart. Only sketchy pages from his last paper remain, but here we assemble some significant clues and triangulate from them to build a broad picture of what he might have been driving at. Our (...) interpretation is that Riemann was a committed idealist and from this philosophical standpoint saw that the scientific enterprise was lame without the “poetry of hypothesis”. He believed that human thought was fundamentally the dynamics of “mind-masses” and that the human mind interpenetrated, and became part of, the microscopic physical domain of the cochlea. Therefore, a full description of hearing must necessarily include the perceptual dimensions of what he saw as a single manifold. The manifold contains all the psychophysical aspects of hearing, including the logarithmic transformations that arise from Fechner’s law, faithfully preserving all the subtle perceptual qualities of sound. For Riemann, hearing was a unitary physical and mental event, and parallels with modern ideas about consciousness and quantum biology are made. A unifying quantum mechanical model for an atom of consciousness—drawing on Riemann’s mind-masses and the similar “psychons” proposed by Eccles—is put forward. (shrink)

Neutral monism is a position in metaphysics defended by Mach, James, and Russell in the early twentieth century. It holds that minds and physical objects are essentially two different orderings of the same underlying neutral elements of nature. This paper sets out some of the central concepts, theses and the historical background of ideas that inform this doctrine of elements. The discussion begins with the classic neutral monism of Mach, James, and Russell in the first part of the paper, then (...) considers recent neo-Russellian versions in the second half. The chances for a revival of neutral monism are probably slight; its key ideas and starting points lie far from those in contemporary philosophy of mind. A better route might be through the philosophy of science and a deeper understanding of causation. (shrink)

Mind-body parallelism is the view that mind and body stand in the same “order and connection,” as Spinoza put it, or that corresponding mental and physical states have corresponding causal explanations in terms of other mental and physical states. This dissertation investigates the nature and role of mind-body parallelism, as well as other forms of parallelism, in Spinoza’s philosophy of mind. In doing so, it also considers how Spinoza’s views relate to current discussions. In present-day philosophy of mind, mind-body parallelism (...) is almost never defended. It is seen as a historical dead-end with insurmountable problems. By contrast, I argue that parallelism powerfully responds to the post-Cartesian mind-body problem (which remains with us today) and that it points a way forward in current debates. The dissertation contains five independent chapters. After an introduction that situates parallelism in relation to both Spinoza’s time and to present discussions, Chapter 1 presents an argument for parallelism aimed at a present-day audience. Chapter 2 discusses Spinoza’s own arguments for parallelism. Both chapters help to clarify what parallelism is, in part by distinguishing between several versions of the view. Chapter 3 discusses what is often considered parallelism’s most problematic feature, its rejection of mind-body interaction. I argue that by distinguishing between the post-Cartesian context in which Spinoza wrote and present-day discussions, we can see that parallelism is compatible with mental causation. Chapters 4 and 5, finally, discuss specific ways in which parallelism is at work in Spinoza’s view of the mind. In Chapter 4, I argue that parallelism is at work in Spinoza’s interesting and distinctive positions on the nature of agency and motivation. In Chapter 5, I show the role of parallelism in his representationalist theory of consciousness. A guiding thread throughout the dissertation is that parallelism presents a distinctive and interesting way to combine realism, non-reductionism and naturalism in relation to those features of human self-understanding that seem difficult to fit into a naturalistic worldview. (shrink)

It is widely held among philosophers that the conservation of energy is true and important, and widely held among philosophers of science that conservation laws and symmetries are tied together by Noether's first theorem. However, beneath the surface of such consensus lie two slights to Noether's first theorem. First, there is a 325+-year controversy about mind-body interaction in relation to the conservation of energy and momentum, with occasional reversals of opinion. The currently popular Leibnizian view, dominant since the late 19th (...) century, claims to find an objection to broadly Cartesian views in their implication of energy non-conservation. Here energy conservation is viewed as an oracle, an unchallengeable black box. But Noether's first theorem and its converse show that conservation and symmetry of the laws stand or fall together. Absent some basis for expecting conservation in brains that has a claim on the Cartesian, the objection is circular. An empirically based argument is possible, but is a different argument with little force except insofar as it is rooted in neuroscience. Second, General Relativity has a 100+-year-long controversy about whether gravitational energy exists and is objectively localized. The usual view is that gravitational energy exists but is not objectively localized, though some deny its existence. Without positive answers to both questions, generally applicable conservation laws do not exist: energy is not conserved. This conclusion is startling in itself and a problem for conserved quantity theories of causation. Yet Noether's first theorem applies to General Relativity, which has uncountably many symmetries of its laws and so has conservation laws, indeed uncountably many of them. Many authors downplay these laws due to their quirky properties; some authors even attempt to explain the laws' supposed nonexistence in terms of an absence of symmetries of the geometry, which is a distraction. Thus Noether's first theorem is widely ignored, left uninterpreted, or distorted in relation to General Relativity. Taking the theorem seriously seems possible, however, restoring the conservation of energy, or rather, energies. How do these controversies relate? One sometimes finds claims that General Relativity's supposed lack of conservation laws answers Leibniz on behalf of Descartes. Taking seriously the superabundance of formal conservation laws in General Relativity, however, suggests that General Relativity resists mind-to-body causation. This conclusion can be proven apart from interpretive controversies. The resistance is, however, finite and tends to be swamped by larger world-view considerations. (shrink)

The paper presents philosophical views which have been propagated in the first decade of the 20 th -century by Austrian experimental physicist Franz-Serafin Exner. According to Exner all apparently deterministic laws are only a kind of the macroscopic limit of the indeterministic random events and processes in nature. The paper attempts to show whether Exner’s ideas have influenced the views on randomness and probability developed by renowned Polish physicist Marian Smoluchowski who belonged to informal circle of Exner’s students and assistants.

The chapter begins with a sketch of the empirical, theoretical, and philosophical background to nineteenth-century theories of perception, focusing on visual perception. It then considers German sensory physiology and psychology in the nineteenth century and its reception. This section gives special attention to: assumptions about nerve–sensation relations; spatial perception; the question of whether there is a two-dimensional representation in visual experience; psychophysics; size constancy; and theories of colour perception. The chapter then offers a brief look at the interaction between perceptual (...) theory and philosophical issues in epistemology and the metaphysics of mind in Britain and America, focusing on: the notion of a muscle sense; the problem of the external world; and forms of perceptual realism. It ends with an overview of psychological theories of perception in the early twentieth century and the Gestalt reaction, culminating with J. J. Gibson. (shrink)