Gary Hatfield

The term “perceptual constancy” was used by the Gestalt theorists in the early part of the twentieth century (e.g., Koffka 1935, 34, 90) to refer to the tendency of perception to remain invariant over changes of viewing distance, viewing angle, and conditions of illumination. This tendency toward constancy is remarkable: every change in the viewing distance, position, and illumination is necessarily accompanied by a change in the local proximal (retinal) stimulation, and yet perception remains relatively stable. The tendency toward perceptual constancy encouraged the Gestalt theorists to look beyond local proximal stimulation in grounding their theories of perception. In the ensuing decades, much has been learned about the constancies. Evidence for this assertion may be found in the contributions to the current volume as well as in earlier volumes (e.g., Epstein 1977; Walsh and Kulikowsky 1998). These advances notwithstanding, significant questions remain open. Our aim here is to note some advances and specify some open questions.

Some experiments in perceptual psychology measure perceivers’ phenomenal experiences of objects versus their cognitive assessments of object properties. Analyzing such experiments, this article responds to Pizlo’s claim that much work on shape constancy before 1985 confused problems of shape ambiguity with problems of shape constancy. Pizlo fails to grasp the logic of experimental designs directed toward phenomenal aspects of shape constancy. In the domain of size perception, Granrud’s studies of size constancy in children and adults distinguish phenomenal from cognitive factors

This chapter deals with Immanuel Kant's remarks on touch and vision in the context of his pragmatic anthropology, by considering his views of the scope, aims, and methods of that fledgling discipline. Kant supports his discussion with appeals to observation and experience that form a kind of everyday phenomenology of sensory experience. The chapter considers Kant's notion of the relation between the pragmatic and the theoretical, including his remarks that a pragmatic anthropology does not present theoretical or scholastic knowledge but focuses on worldly knowledge. Kant derived the framework for his discussion of the five external senses from his lectures on metaphysics, especially those on empirical psychology. In both empirical psychology and anthropology he categorizes the senses into those that are comparatively objective and those that are comparatively subjective: the objective senses provide more cognition, and provide occasion for reflection, but the subjective senses have more sensation than reflection.

Seeing happens effortlessly and yet is endlessly complex. Among the most fascinating aspects of visual perception is its stability and constancy. As we shift our gaze or move about the world, the light projected onto the retinas is constantly changing. Yet the surrounding objects appear stable in their properties. Psychologists have long been interested in the constancies. They have asked questions such as: How good is constancy? Is constancy a fact about how things look, or is it a product of our beliefs and judgments about how things look? How can the contents of visual experience be studied experimentally? Philosophers have long been interested in characterizing visual experience and have become widely interested in the constancies more recently. As psychologists and philosophers have interacted, new questions have arisen: If experience is not as of retinal stimulation (proximal mode), but does not always exhibit constancy (or at least not in all respects), how shall we describe this intermediate state? Also, should we regard any departure from constancy as a failure of the visual system, or might it be a reasonable or adaptive response? In what circumstances is seeing highly conditioned by cognitive factors such as background assumptions, and in what circumstances not? Our volume focuses on size constancy and color constancy. It considers methodologies for studying conscious visual perception, efforts to describe visual experience in relation to constancy, what it means that constancy is not always perfect, and the conceptual resources needed for explaining visual experience.

It seems intuitively obvious that metameric matching of color samples entails a loss of information, for spectrophotometrically diverse materials appear the same. This intuition implicitly relies on a conception of the function of color vision and on a related conception of how color samples should be individuated. It assumes that the function of color vision is to distinguish among spectral energy distributions, and that color samples should be individuated by their physical properties. I challenge these assumptions by articulating a different conception of the function of color vision, according to which color vision serves to partition object surfaces into discrimination classes.

The chapter advances two theses involving Descartes and the mind. The first concerns Descartes' conception of mental faculties, particularly the intellect. As I read the _Meditations_, a fundamental aim of that work is to make the reader aware of the deliverances of the pure intellect, perhaps for the first time. Descartes' project is to alter the reader's Aristotelian beliefs about the faculty of the intellect and its relation to the senses, while at the same time coaxing her to use the pure intellect to perceive the first truths of metaphysics. His anti-Aristotelian understanding of the power of pure intellect undergirds his attempted revolution in metaphysics and physics. The second thesis pertains to Descartes' naturalism about the mind. Descartes typically is seen as having excluded mind from nature, thereby deanimating (literally, "de-souling") the physical world and making it safe for a full-scale mechanistic physics. This attitude effectively makes the mind into "a convenient receptacle for the chips and whittlings of science, rather than a possible object of scientific knowledge" (E. A. Burtt). In contrast, I argue that Descartes included (at least some functions and states of) mind as part of nature, that despite his dualism he continued an established tradition of treating the operations of the senses as open to empirical investigation, and that in virtue of his dualism he initiated a new line of thought leading to the search for specifically psychophysical laws, that is, laws linking non-mental bodily states to states of mind. The precise senses in which Descartes did and did not include *mind* under the rubric *nature* is problematic; but he did use language suggesting that even the intellect is a natural constituent of the human being, as when he ascribed intellectual cognitions to "the natural light."

Review of: Stephen Gaukroger: The Collapse of Mechanism and the Rise of Sensibility: Science and the Shaping of Modernity, 1680-1760. Oxford: Clarendon, 2010, pp. ix+505. £47.00 (hb). ISBN 9780199594931. This volume is the second of a projected six-volume work on the shaping of modern cognitive values through the emergence of a scientific culture, a phenomenon that Gaukroger takes to be specific to the West. The volume ranges from Newton’s initial publications on optics to the French Enlightenment and the publication of the <i>Encyclopédie</i> of Diderot and d’Alembert. During this period, the unity within natural philosophy, secured by the view that matter theory should underlie all natural philosophy, is challenged, as is the unity between natural philosophy and physico-theology, the latter unity being the primary source of the cultural legitimacy that had allowed natural philosophy to flourish. The first type of unity was sundered as Newtonian natural philosophy disavowed the requirement that mechanics be united with a microscopic corpuscularian basis. Further, during this period, scientific (or natural philosophical) values first came to dominate the cognitive values of an entire culture, largely through the <i>persona</i> of the <i>philosophe</i> as the embodiment of reason, albeit a sensibilized reason arising from the new non-mechanistic natural philosophy of the mid-eighteenth century and no longer tied to physico-theology. The book does a better job charting the trend toward disunity than it does charting the rise of sensibility.

Shape and slant judgments of rotated or frontoparallel ellipses were elicited from three groups of 10 subjects. A masking stimulus was introduced to control processing time. Backward masking trials were presented with interstimulus intervals of 0, 25, and 50 msec, Reduction of processing time altered shape judgments in the direction of projective shape and slant judgments in the direction of frontoparallelness. This finding is consistent with the shape-slant invariance hypothesis. In order to study the effects of processing load, one group of subjects was given prior knowledge of the kind of judgment to be made on each trial, one group had no prior knowledge, and a third group made both judgments on each trial. The effects of the processing load manipulation were interpreted in terms of the role of attention in perceptual encoding. Consistent with previous findings, allocation of attention did not affect perceptual encoding.

The theory of knowledge in early twentieth-century Anglo American philosophy was oriented toward phenomenally described cognition. There was a healthy respect for the mind-body problem, which meant that phenomena in both the mental and physical domains were taken seriously. Bertrand Russell's developing position on sense-data and momentary particulars drew upon, and ultimately became like, the neutral monism of Ernst Mach and William James. Due to a more recent behaviorist and physicalist inspired "fear of the mental", this development has been down-played in historical work on early analytic philosophy. Such neglect assumes that the "linguistic turn" is a proper and permanent effect of twentieth-century philosophy, an assumption that distorts early analytic historiography, and begs a substantive philosophical question about thought and cognition.

The chapter focuses on attributions of the transparency of thought to early modern figures, most notably Descartes. Many recent philosophers assume that Descartes believed the mind to be “transparent”: since all mental states are conscious, we are therefore aware of them all, and indeed incorrigibly know them all. Descartes, and Berkeley too, do make statements that seem to endorse both aspects of the transparency theses (awareness of all mental states; incorrigibility). However, they also make systematic theoretical statements that directly countenance “unnoticed” thoughts or mental states, that is, thoughts or mental states of which the subject is unaware and has no knowledge. Descartes, having identified the essence of mind with thought or representation, distinguishes bare states of mind from states of which we have reflective awareness, thereby providing a theoretical tool for understanding both his seeming endorsement of transparency and his actual denial of it: Descartes distinguished between a basic perceptual state, or a basic awareness, and reflectively conscious states that involve explicit noticing and cognizing on the part of the subject. Leibniz (as is better known) directly endorsed a similar distinction between bare perception and reflective consciousness, using the term “perception” for the first and “apperception” for the second. In these cases, bare perceptions are not transparently available to the subject, and so in fact the subject does not have knowledge, hence does not have incorrigible knowledge, of all its occurrent mental states. This chapter gives evidence to support these claims; elaborates the complex psychology of the subject found in Descartes and other early moderns; and notes some ways in which these early moderns contributed to the genesis of the modern subject. Finally, it compares McDowell’s conception of the Cartesian mind with the conceptions of mind found in the writings of Descartes, Berkeley, and Leibniz, finding that his characterization caricatures the positions of early modern philosophers. McDowell's characterization has four elements: consciousness as essence of mind; intentionality as exclusively mental; the veil of perception; and the transparency of mind. Only the second point, about intentionality, fully fits Descartes. As a consequence of his own misdirection, McDowell misses the actual basis of his difficulty in connecting mind with world, which arises from a point of agreement between him and Descartes: the removal of intentionality from material sensory systems. But whereas Descartes could relocate (nonconceptual) sensory intentionality in mental states, McDowell is left to account for it with his overly cognitivized scheme of perceptual content as exclusively conceptual. (Paper first given at the European Society for Early Modern Philosophy, 2007.)

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.

It is difficult to evaluate the role of activity - of force or of that which has causal efficacy - in Descartes’ natural philosophy. On the one hand, Descartes claims to include in his natural philosophy only that which can be described geometrically, which amounts to matter (extended substance) in motion (where this motion is described kinematically).’ Yet on the other hand, rigorous adherence to a purely geometrical description of matter in motion would make it difficult to account for the interactions among the particles that constitute Descartes’ universe, since the notions of extension and kinematical motion do not in themselves imply any causal agency. There is, after all, no reason to expect that a particle whose single essence is extension, even if we suppose it to be moving, should impart motion to another particle, while conversely, there is no reason to expect a resting particle to hinder the motion of an impinging one. Descartes' hankering for an austere ontology of matter in motion is in danger of excluding causal agency (force, conceived dynmically) from matter. To the modern reader it may seem obvious that Descartes did not get himself into such a fix, since matter in motion so readily reminds us of kinetic energy or of some more primitive notion of force. Yet by no means is it obvious that Descartes attributed causal efficacy to matter in motion per se. Serious scholars have held opposite positions on this issue. Westfall, Gabbey, and others’ have argued that although on the metaphysical plane Descartes attempted to eliminate force from his mechanical universe, nonetheless ‘force is a real feature’ of his mechanical world. The thrust of this view is that Descartes conceived of force as ‘the capacity of a body in motion to act’, by means of impact, upon other bodies. An opposing interpretation, defended here, is that Descartes did in fact deny causal agency to moving matter per se, restricting agency to immaterial substances such as the human mind, angels, and God. The intention of this interpretation is not to de-emphasize the role of matter in motion in Descartes’ explanation of nature, but rather to stress the fact that Descartes did not conceive of this moving matter dynamically. Reprinted in Descartes, ed. by J. Cottingham, Oxford Readings in Philosophy (Oxford: Oxford University Press, 1998), 281–310.

Visual space can be distinguished from physical space. The first is found in visual experience, while the second is defined independently of perception. Theorists have wondered about the relation between the two. Some investigators have concluded that visual space is non-Euclidean, and that it does not have a single metric structure. Here it is argued that visual space exhibits contraction in all three dimensions with increasing distance from the observer, that experienced features of this contraction are not the same as would be the experience of a perspective projection onto a fronto-parallel plane, and that such contraction is consistent with size constancy. These properties of visual space are different from those that would be predicted if spatial perception resulted from the successful solution of the inverse problem. They are consistent with the notion that optical constraints have been internalized. More generally, they are also consistent with the notion that visual spatial structures bear a resemblance relation to physical spatial structures. This notion supports a type of representational relation that is distinct from mere causal correspondence. The reticence of some philosophers and psychologists to discuss the structure of phenomenal space is diagnosed in terms of the simple materialism and the functionalism of the 1970s and 1980s

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.

The concept of representation has become almost inextricably bound to the concept of symbol systems. the concepts is nowhere more prevalent than in descriptions of "internal representations." These representations are thought to occur in an internal symbol system that allows the brain to store and use information. In this paper we explore a different approach to understanding psychological processes, one that retains a commitment to representations and computations but that is not based on the idea that information must be stored and manipulated in symbol systems. In particular, we suggest that the notion of a symbol system as currently understood construes psychological processes in terms of a specific type of computational system, in which a control function "reads," "interprets," and manipulates discrete entities called "symbols." We argue that other types of computational systems may provide a more appropriate characterization of psychological processes. One implication of our argument is the need to consider the constraints placed on computational theories in psychology by the nature of the computing device itself, the human brain. Perhaps surprisingly, this implication leads us to the conclusion that a "functionalist" conception of psychological processes (discussed below) does not entail that physiology is irrelevant to psychology, as has been maintained by prominent adherents of the symbol-systems approach.

Descartes understood the subject matter of physics (or natural philosophy) to encompass the whole of nature, including living things. It therefore comprised not only nonvital phenomena, including those we would now denominate as physical, chemical, minerological, magnetic, and atmospheric; it also extended to the world of plants and animals, including the human animal (with the exception of those aspects of the human mind that Descartes assigned to solely to thinking substance: pure intellect and will). Descartes wrote extensively on physiology and on the physiology and psychology of the senses. This chapter examines the notions of *physiology* and *psychology* in medical and natural philosophical works of Descartes' day; follows his efforts to bring physiology into his mechanistic idiom; considers the relation between physiology of the animal machine and psychological functions that yield functionally appropriate behavior; goes into his physiology and psychology of vision; and elaborates the tension in Descartes' works between his metaphysically supported micro-corpuscularism and his discussion of the animal machine as an organic unity comprising various functionally and teleologically characterized systems. The chapter draws on Descartes' works in both metaphysics and natural philosophy, including his Treatise on Man (originally published as L'Homme, 1664).

This paper develops an appearance view of perception (focusing on vision). When we see an object, we see it by having it appear some way to us. We see the object, not the appearance; but we see the object via the appearance. The appearance is subjectively conditioned: aspects of it depend on attributes of the subject. We mentally have the appearance and can reflect on it as an appearance. But in the primary instance, of veridical perception, it is the object that we focus on and experience. I contrast this view with naive realism (sometimes called disjunctivism) (Brewer, Campbell, Noe) and with intentionalist or representationalist views, which I call the physical content view (Dretske, Tye, Crane, Hill, Burge). I agree with these views in rejecting sense-data intermediaries and in affirming direct perception, but I argue that direct perception occurs via appearances, making mine a critical direct realism. The other views attempt to explain the spatial content of perception (shape, size, distance) entirely through the physical properties of objects and their physical relation to the perceiver (viewing position). I argue instead that there are ineliminably subjective aspects of normal spatial perception, which are systematically manifested as a lack of full phenomenal constancy. This systematic underconstancy can’t be accounted for at all by a consistent naive realism; for the physical content view, it requires that most of our ordinary perception is classified as illusory, violating the spirit of that view. Accepting phenomenal underconstancy as pervasive, I suggest that our ability to perceive the mind-independent properties of objects depends on developed conceptual abilities. In the final section, I compare my appearance view with the adverbialism of Chisholm and the critical direct realism of Roy Wood Sellars.

Descartes is widely regarded to be the father of modern philosophy and his Meditations is among the most important philosophical texts ever written. _The Routledge Guidebook to Descartes’ Meditations_ introduces the major themes in Descartes’ great book and acts as a companion for reading this key work, examining: The context of Descartes’ work and the background to his writing; Each separate part of the text in relation to its goals, meanings and impact; The reception the book received when first seen by the world; The relevance of Descartes’ work to modern philosophy, it’s legacy and influence. With further reading included throughout, this text follows Descartes’ original work closely, making it essential reading for all students of philosophy, and all those wishing to get to grips with this classic work. This edition revises the earlier guidebook entitled _Descartes and the Meditations_ (2003). It has been thoroughly revised, and contains expanded treatment of the method of doubt, theory of ideas, and new discussion of Descartes' theory of vision.

Behaviorism was a peculiarly American phenomenon. As a school of psychology it was founded by John B. Watson (1878-1958) and grew into the neobehaviorisms of the 1920s, 30s and 40s. Philosophers were involved from the start, prefiguring the movement and endeavoring to define or redefine its tenets. Behaviorism expressed the naturalistic bent in American thought, which came in response to the prevailing philosophical idealism and was inspired by developments in natural science itself. There were several versions of naturalism in American philosophy, and also several behaviorisms. Most behaviorists paid homage to Darwinian functionalism; all forswore introspection and made learned changes in behavior the primary subject matter and explanatory domain of psychology. They differed in their descriptions of behavior, modes of explanation, and attitudes toward mentalistic concepts. Watson was a strict materialist who wanted to eliminate all mentalistic talk from psychology. Edward Chace Tolman (1886-1959) regarded mind as a biological function of the organism. He permitted mentalistic terms such as 'purpose' in behavioral description, and posited intervening processes that included 'representations' of the environment, while requiring such processes be studied only as expressed in behavior. Clark L. Hull (1884-1952) developed a hypothetical-deductive version of behaviorism, akin to Tolman's functionalism in positing intervening variables but without his cognitivist constructs. B. F. Skinner (1904-90) rejected intervening variables and developed his own account of the behavior of the whole organism, based on the laws of operant conditioning. The naturalism in American philosophy of the early twentieth century showed respect for the natural sciences, especially biology and psychology. John Dewey (1896, 1911), George Santayana (1905, 1920), and F. J. E. Woodbridge (1909, 1913) expressed this attitude. It animated the neorealism of E. B. Holt and Ralph Barton Perry, who gave special attention to psychology, and the evolutionary naturalism and critical realism of Roy Wood Sellars. This naturalism differed from Watson's in regarding mind as part of nature from a Darwinian and functionalist perspective, and treating behavior as the product of the mental functioning. It fed Tolman's version of behaviorism. It was not materialistic or physical-reductionist. Only later, with Quine and logical empiricism, was behaviorism seen as essentially physicalistic.

Mandelbaum adopted a middle course between physicalistic scientific realism and phenomenalistic "ordinary language" direct realism. He affirmed the relevance of scientific knowledge for epistemology, but did not attempt to reduce the content of perception to physical properties. Rather, he developed a critical direct realism, according to which we see bodies by means of having phenomenal experience. This phenomenal experience was not, however, to be equated with the sense-data of the usual representative realism. Rather, it was a perception of material objects by means of their qualities. In this way, he agreed with the phenomenological position of the Gestalt psychologist Wolfgang Koehler, who rejected the view that sense-data by themselves could provide an epistemic basis for knowledge claims. Koehler's position, too, may be described as a critical realism. As would Mandelbaum, he sought to give proper due to the phenomenal while also affirming its basis in a physical world of objects and brain processes. In its insistence on the reality and scientific respectability of the phenomenal, the critical realism of Mandelbaum and Koehler is distinct from the contemporaneous physicalism of Place and Smart.

In the early modern period, many authors held that sensation or sensory reception is in some way passive and that perception is in some way active. The notion of a more passive and a more active aspect of perception is already present in Aristotle: the senses receive forms without matter more or less passively, but the “primary sense” also recognizes the salience of present objects. Ibn al-Haytham distinguished “pure sensation” from other aspects of sense perception, achieved by “discernment, inference and recognition,” which included perception of properties such as size and distance as well as similarity, difference, and beauty. Descartes regarded light and color as experiences passively caused in the mind by bodily processes, but he also included distance, perceived through accommodation and convergence, as an immediately caused sensory idea. On the perception side, most theorists held that size and distance perception occurs through unnoticed psychological operations, whether mediated by judgment or associative processes. Association is, in a sense, passive, as it occurs through nonreflective habit formation. But such habits mark a contribution of the subject to perception and are in that way active. The decision of whether sensation and perception are active or passive is highly sensitive to what counts as activity and to what is included as sensation or perception. There is no simple formula, but the generalization that sensation is for the most part passive and perception for the most part active may stand as an imprecise summary of early modern thought on the topic

There is a strong philosophical intuition that direct study of the brain can and will constrain the development of psychological theory. When this intuition is tested against case studies on the neurophysiology and psychology of perception and memory, it turns out that psychology has led the way toward knowledge of neurophysiology. An abstract argument is developed to show that psychology can and must lead the way in neuroscientific study of mental function. The opposing intuition is based on mainly weak arguments about the fundamentality or objectivity of physics or physiology in relation to psychology. -/- Philosophy of Science, Vol. 67, Supplement. Proceedings of the 1998 Biennial Meetings of the Philosophy of Science Association. Part II: Symposia Papers (Sep., 2000).

Two stories have dominated the historiography of early modern philosophy: one in which a seventeenth century Age of Reason spawned the Enlightenment, and another in which a skeptical crisis cast a shadow over subsequent philosophy, resulting in ever narrower "limits to knowledge." I combine certain elements common to both into a third narrative, one that begins by taking seriously seventeenth-century conceptions of the topics and methods central to the rise of a "new" philosophy. In this revisionist story, differing approaches to the central subject matter of early modern metaphysics--knowledge of substances through their essences and causal powers--arise as a result of disagreements about the powers of the human cognitive faculties. Methodological writings are seen as attempts to direct readers in the proper use of their cognitive faculties. The early modern rejection of the Aristotelian theory of cognition ranks equally in importance with rejection of Aristotelian doctrines about nature. Skepticism is more often than not a tool to be used in teaching the reader the proper use of the cognitive faculties, or indeed in convincing the reader of the existence or inexistence of certain cognitive faculties or powers. Instead of early modern "epistemology" or "theory of knowledge," one speaks, with seventeenth century writers, of theories of the cognitive faculties and their implications for the possibility of human knowledge. The early modern rejection of Aristotelian logic can then be seen as reflecting a negative assessment about the fit between syllogistic reasoning and logic as an art of reasoning or thinking which refines the use of the cognitive faculties. Central to this new historiography is the story of the relation between the intellect and senses as cognitive faculties or powers. The development of philosophy from Descartes to Kant can be portrayed as a series of claims about the power of the intellect to know the essences of things, with resulting consequences for ontology and the foundations of natural philosophy. I illustrate this revised narrative by comparing three conceptions of the intellect in three philosophical settings, provided by several late scholastic Aristotelians, Descartes, and Locke. I have two aims: first, to exhibit the central role played by the conception of intellect or understanding in these authors, and, second, to locate their discussions of the cognitive faculties in relation to recent understandings of psychology, epistemology, logic, mind, and their relations. Early modern writings do not easily fit into the modern categories of epistemology and psychology; more generally, the early modern concern with the workings of mind does not coincide with recent conceptions of naturalism. These findings can help us to see problems with our current categories.

This chapter compares rationalist theories of sense perception to previously held theories of perception (especially of vision) and examines rationalist accounts of sensory qualities and sensory representation, of the role of the sense-based passions in guiding behavior, of the epistemological benefits and dangers of sense perception, and of mind–body relations. Each section begins with Descartes, the first major rationalist of the seventeenth century. The other major rationalists, Malebranche, Spinoza, and Leibniz, and also lesser known figures such as Pierre Regis, Jacques Rohault, and Antoine Le Grand, were well acquainted with Descartes' work. Indeed, the first three were each deeply influenced by Descartes in their early years before developing their own philosophical systems, and the latter three were all advocates of Descartes' philosophy (perhaps with slight revision). Each of the major rationalists, while sharing some positions in common, developed a distinctive metaphysics of perception and of the mind–body relation. Earlier sections chart these differences and a final section sums up common features and touches on the continuing significance of their views.

The chapter concerns some aspects of Russell’s epistemological turn in the period after 1911. In particular, it focuses on two aspects of his philosophy in this period: his attempt to render material objects as constructions out of sense data, and his attitude toward sense data as “hard data.” It examines closely Russell’s “breakthrough” of early 1914, in which he concluded that, viewed from the standpoint of epistemology and analytic construction, space has six dimensions, not merely three. Russell posits a three-dimensional personal or “perspective” space that is inhabited by sense data. This space then forms the basis for constructing the three dimensional space of physics (and of public things). I am concerned with the specifics of this construction: with the properties of the private spaces, the relations among those spaces, and their relation to physical space and to constructed “things,” such as pennies or tables. There are difficulties of interpretation with respect to these relations, which stem from the difficulty of finding a coherent interpretation of Russell’s claim that objects such as tables and pennies look smaller at a greater distance (or look trapezoidal or elliptical from some points of view). I don’t mean to challenge the phenomenal claim that objects do, in some sense, look small in the distance. Rather, I raise difficulties with Russell’s analysis of this fact, in which he appeals to both phenomenal experience and the findings of sensory psychology. I hold that if he wishes to maintain his phenomenal claim about objects appearing smaller with greater distance, he must alter or redescribe aspects of his construction of ordinary things. However, if his construction of things and physical space is based on a problematic description of the private spaces, then his claim that private or perspective spaces are very well known and provide the hard data for knowledge of the physical world faces a challenge.