This paper presents a new account of aesthetic pleasure, according to which it is a distinct psychological structure marked by a characteristic self-reinforcing motivation. Pleasure figures in the appreciation of an object in two ways: In the short run, when we are in contact with particular artefacts on particular occasions, aesthetic pleasure motivates engagement and keeps it running smoothly—it may do this despite the fact that the object we engagement is aversive in some ways. Over longer periods, it plays a (...) critical role in shaping how we engage with objects to get this kind of pleasure from them. This account is yoked to a broadly functional understanding of art: it is not the nature of the object that makes it art, but the nature of the response that it is designed to elicit. The view does not, however, rest on individual psychology alone, as some other functional accounts do. Crucially, it is argued that shared cultural context is a key determinant of the pleasure we derive from aesthetic artefacts. The pleasure of art is always communal and communicative. (shrink)

Memory seems intuitively to consist in the preservation of some proposition (in the case of semantic memory) or sensory image (in the case of episodic memory). However, this intuition faces fatal difficulties. Semantic memory has to be updated to reflect the passage of time: it is not just preservation. And episodic memory can occur in a format (the observer perspective) in which the remembered image is different from the original sensory image. These difficulties indicate that memory cannot be preserved content. (...) It is proposed that what is preserved in memory isan underlying "trace", and that in every act of remembering, memorial content is reconstructed from the preserved trace. (shrink)

Over the past fifteen years there has been a considerable amount of debate concerning what theoretical population dynamic models tell us about the nature of natural selection and drift. On the causal interpretation, these models describe the causes of population change. On the statistical interpretation, the models of population dynamics models specify statistical parameters that explain, predict, and quantify changes in population structure, without identifying the causes of those changes. Selection and drift are part of a statistical description of population (...) change; they are not discrete, apportionable causes. Our objective here is to provide a definitive statement of the statistical position, so as to allay some confusions in the current literature. We outline four commitments that are central to statisticalism. They are: 1. Natural Selection is a higher order effect; 2. Trait fitness is primitive; 3. Modern Synthesis (MS)-models are substrate neutral; 4. MS-selection and drift are model-relative. (shrink)

How many senses do humans possess? Five external senses, as most cultures have it—sight, hearing, touch, smell, and taste? Should proprioception, kinaesthesia, thirst, and pain be included, under the rubric bodily sense? What about the perception of time and the sense of number? Such questions reduce to two. 1. How do we distinguish a sense from other sorts of information-receiving faculties? 2. By what principle do we distinguish the senses? Aristotle discussed these questions in the De Anima. H. P. Grice (...) revived them in 1967. More recently, they have taken on fresh interest as a result of a collection of essays edited by Fiona Macpherson. This entry reviews some approaches to these questions and advances some new ideas for the reader’s consideration. It proposes that the senses constitute an integrated learning system, membership in which answers question 1. It also proposes that the modalities can be distinguished from one another in two ways, by the means of information pick-up and by the kinds of activity that a perceiver undertakes to make use of them. (shrink)

Because culture plays a role in determining the aesthetic merit of a work of art, intrinsically similar works can have different aesthetic merit when assessed in different cultures. This paper argues that a form of aesthetic hedonism is best placed to account for this relativity of aesthetic value. This form of hedonism is based on a functional account of aesthetic pleasure, according to which it motivates and enables mental engagement with artworks, and an account of pleasure-learning, in which it reinforces (...) the appreciation of culture specific ways of engaging with art. (shrink)

Molyneux's Question (MQ) concerns whether a newly sighted man would recognize/distinguish a sphere and a cube by vision, assuming he could previously do this by touch. We argue that (MQ) splits into questions about (a) shared representations of space in different perceptual systems, and about (b) shared ways of constructing higher dimensional spatiotemporal features from information about lower dimensional ones, most of the technical difficulty centring on (b). So understood, MQ resists any monolithic answer: everything depends on the constraints faced (...) by particular perceptual systems in extracting features of higher dimensionality from those of lower. Each individual question of this type is empirical and must be investigated separately. We present several variations on MQ based on different levels of dimensional integration—some of these are familiar, some novel adaptations of problems known elsewhere, and some completely novel. Organizing these cases in this way is useful because it unifies a set of disparate questions about intermodal transfer that have held philosophical and psychological interest, suggests a new range of questions of the same type, sheds light on similarities and differences between members of the family, and allows us to formulate a much-augmented set of principles and questions concerning the intermodal transfer of spatiotemporal organization. (shrink)

What colour does a white wall look in the pinkish light of the late afternoon? Philosophers disagree: they hold variously that it looks pink, white, both, and no colour at all. A new approach is offered. After reviewing the dispute, a reinterpretation of perceptual constancy is offered. In accordance with this reinterpretation, it is argued that perceptual features such as color must always be predicated of perceptual objects. Thus, it might be that in pinkish light, the wall looks white and (...) the light looks pink. The paper concludes by discussing some criteria for object identification in perceptual states. (shrink)

A hitherto neglected form of explanation is explored, especially its role in population genetics. “Statistically abstractive explanation” (SA explanation) mandates the suppression of factors probabilistically relevant to an explanandum when these factors are extraneous to the theoretical project being pursued. When these factors are suppressed, the explanandum is rendered uncertain. But this uncertainty traces to the theoretically constrained character of SA explanation, not to any real indeterminacy. Random genetic drift is an artifact of such uncertainty, and it is therefore wrong (...) to reify it as a cause of evolution or as a process in its own right. *Received July 2009. †To contact the author, please write to: Department of Philosophy, University of Toronto, 170 St. George St., Toronto, ON M5R 2M8, Canada; e‐mail: [email protected] (shrink)

Two questions are addressed in this paper. First, what is it to see? I argue that it is veridical experience of things outside the perceiver brought about by looking. Second, what is it to see a material object? I argue that it is experience of an occupant of a spatial region that is a logical subject for other visual features, able to move to another spatial region, to change intrinsically, and to interact with other material objects. I show how this (...) theory is different from the idea that object-seeing is merely the visual segregation of a region of the visual field. Finally, I argue that we do not object-see objects reflected in mirrors, surfaces of back-lit objects, and depictions of objects. (shrink)

Food has savour: a collection of properties (including appearance, aroma, mouth-feel) connected with the pleasure (or displeasure) of eating. After explaining this concept, and outlining a theory of aesthetic pleasure, I argue that, like paradigm examples of art, savour can be assessed relative to a culturally determined set of norms. Also like paradigm examples of art, the assessment of savour has no objective basis in the absence of such cultural norms. My argument in this paper is part of a larger (...) project in which I develop an account of the pleasure of art. It is a virtue (I claim) of my approach that it permits a much greater diversity of artforms than traditional philosophical aesthetics is inclined to allow. This includes food. (shrink)

The sense of touch provides us knowledge of two kinds of events. Tactile sensation (T) makes us aware of events on or just below the skin; haptic perception (H) gives us knowledge of things outside the body with which we are in contact. This paper argues that T and H are distinct experiences, and not (as some have argued) different aspects of the same touch-experience. In other words, T ≠ H. Moreover, H does not supervene on T. Secondly: In T, (...) we are aware of immanent, phenomenal qualities; in H, we come to know of transcendent qualities in things that exist independently of ourselves. Finally: T is non-spatial; it is indexed by parts of the body, but not by position in space. H, by contrast, is spatial. This brings to mind Kant’s contention that things are presented as existing objectively when they are represented spatially. (shrink)

Art is universal across cultures. Yet, it is biologically expensive because of the energy expended and reduced vigilance. Why do humans make and contemplate it? This paper advances a thesis about the psychological origins of perceptual art. First, it delineates the aspects of art that need explaining: not just why it is attractive, but why fine execution and form—which have to do with how the attraction is achieved—matter over and above attractiveness. Second, it states certain constraints: we need to explain (...) pleasure in contemplation, not value extracted from the object by activities other than contemplation. The theory is that aesthetic pleasure is a motivation for learning skills. Two forms of pleasure are postulated. The first accompanies the spontaneous activity necessary for learning a more or less universal basic level of skill. The second accompanies highly skilled activity. This second kind of pleasure is specific to art as such. (shrink)

Kant argued that the perceptual representations of space and time were templates for the perceived spatiotemporal ordering of objects, and common to all modalities. His idea is that these perceptual representations were specific to no modality, but prior to all—they are pre-modal, so to speak. In this paper, it is argued that active perception—purposeful interactive exploration of the environment by the senses—demands premodal representations of time and space.

Perception is the ultimate source of our knowledge about contingent facts. It is an extremely important philosophical development that starting in the last quarter of the twentieth century, philosophers have begun to change how they think of perception. The traditional view of perception focussed on sensory receptors; it has become clear, however, that perceptual systems radically transform the output of these receptors, yielding content concerning objects and events in the external world. Adequate understanding of this process requires that we think (...) of perception in new ways—how it operates, the differences among the modalities, and integration of content provided by the individual senses. Philosophers have developed new analytic tools, and opened themselves up to new ways of thinking about the relationship of perception to knowledge. The Oxford Handbook of the Philosophy of Perception is a collection of entries by leading researchers that reviews these new directions in philosophical thought. The Introduction to the Handbook reviews the history of the subject from its beginnings in ancient Greece to the nineteenth century, and the way that science and philosophy have together produced new conceptions during the last hundred years. It shows how the new thinking about perception has led to a complex web of theories. (shrink)

The senses present their content in the form of images, three-dimensional arrays of located sense features. Peacocke’s “scenario content” is one attempt to capture image content; here, a richer notion is presented, sensory images include located objects and features predicated of them. It is argued that our grasp of the meaning of these images implies that they have propositional content. Two problems concerning image content are explored. The first is that even on an enriched conception, image content has certain expressive (...) limitations. In particular, it cannot express absolute location and time (as opposed to spatiotemporal relations) or logical complexity. Yet, perceptual experience does seem to express certain absolute locations—namely, here and now. How can it do so? Secondly, image content cannot exhaust the significance of perceptual states. This is proved by noting that perception, memory, and anticipation can have the same image content. Yet they have different significance. These problems show that some of the significance of sensory states comes from outside the image. (shrink)

I can be wrong about things I seem to perceive; the conditions might lead me to be mistaken about them. Since I can't rule out the possibility that the conditions are misleading, I can't be sure that I am perceiving this thing in my hand correctly. But suppose that I am able to examine it actively—handling it, looking closer, shining a light on it, and so on. Then, my level of uncertainty goes down; in the limit it is eliminated entirely. (...) Of course, I might be mistaken because I am a brain in a vat, or because some other sceptical scenario obtains. But sceptical scenarios apply not just to this thing in my hand, but to everything all at once. Define "empirical certainty" as the absence of the kind of doubt that spreads to all empirical states of affairs. Sensory exploration, or active examination, can in principle lead to empirical certainty. (shrink)

Vision is organized around material objects; they are most of what we see. But we also see beams of light, depictions, shadows, reflections, etc. These things look like material objects in many ways, but it is still visually obvious that they are not material objects. This chapter articulates some principles that allow us to understand how we see these ‘ephemera’. H.P. Grice’s definition of seeing is standard in many discussions; here I clarify and augment it with a criterion drawn from (...) Fred Dretske. This enables me to re-analyse certain ephemera that have received counter-intuitive treatments in the work of Kendall Walton (photographs), Brian O’Shaughnessy (light), and Roy Sorenson (occlusions). (shrink)

In this review of Hutto and Myin's Radicalizing Enactivism, I question the adequacy of a non-representational theory of mind. I argue first that such a theory cannot differentiate cognition from other bodily engagements such as wrestling with an opponent. Second, I question whether the simple robots constructed by Rodney Brooks are adequate as models of multimodal organisms. Last, I argue that Hutto and Myin pay very little attention to how semantically interacting representations are needed to give an account of choice (...) and action. (shrink)

When I act on something, three kinds of idea (or representation) come into play. First, I have a non-visual representation of my goals. Second, I have a visual description of the kind of thing that I must act upon in order to satisfy my goals. Finally, I have an egocentric position locator that enables my body to interact with the object. It is argued here that these ideas are distinct. It is also argued that the egocentric position locator functions in (...) the same way as a demonstrative, and that the involvement of such demonstratives in visual content negates naive realism. (This is a nearly final draft of a paper that is to be published in Raftopoulos and Machamer (eds), Perception, Realism, and the Problem of Reference (forthcoming from Cambridge UP. It is a shorter revised version of "Visual Reference", posted earlier.). (shrink)

The author investigates greek ontologies that apparently rely on a conflation of "binary" (x is f) and "monadic" (x is) uses of 'is'. He uses Aristotelian and other texts to support his proposal that these ontologies are explained by the Greeks using two alternative semantic analyses for 'x is F'. The first views it as asserting a relation between x and F, the second as asserting that a "predicative complex" exists, where a predicative complex is a complex consisting of x (...) and F. The article concludes by indicating some uses for the novel concept of predicative complex in aristotelian interpretation. (shrink)

An artwork in one culture and form, say European classical music, cannot be evaluated in the context of another, say Hindustani music. While a person educated in the traditions of European music can rationally evaluate and discuss her response to a string quartet by Beethoven, her response to music in a foreign culture is merely subjective. She might "like" the latter, but her response is merely subjective. In this paper, I discuss the role of artforms: why response can be "objectively" (...) discussed within artforms, but is nonetheless subjective across them. My discussion falls into two parts. First, I offer a psychological account of aesthetic response to art: cultural learning stabilizes this response across individuals who are educated in an artform. Second, I offer a cultural-evolutionary account of the diversity of artforms, adapting Darwin's Principle of the Divergence of Character to explain the multiplicity of art forms. (shrink)

Argues that biological organs, including mental capacities, should be identified by homology (not function).

What is the relationship between color experience and color? Here, I defend the view that it is semantic: color experience denotes color in a code innately known by the perceiver. This semantic theory contrasts with a variety of theories according to which color is defined as the cause of color experience (in a special set of circumstances). It also contrasts with primary quality theories of color, which treat color as a physical quantity. I argue that the semantic theory better accounts (...) for the kinds of knowledge we have regarding both the color of objects that we see and of the colors themselves. (shrink)

The Introduction discusses determinables and similarity spaces and ties together the contributions to Color Ontology and Color Science.

Argues that Aristotle regarded the universe, or Totality, as a single substance with form and matter, and that he regarded this substance together with the Prime Mover as a self-mover.

This is a response to invited and submitted commentary on "The Pleasure of Art," published in Australasian Philosophical Reviews 1, 1 (2017). In it, I expand on my view of aesthetic pleasure, particularly how the distinction between facilitating pleasure and relief pleasure works. In response to critics who discerned and were uncomfortable with the aesthetic hedonism that they found in the work, I develop that aspect of my view. My position is that the aesthetic value of a work of art (...) is its capacity to elicit from a suitably well-informed consumer a specific kind of pleasure. (shrink)

Aristotle held that perception consists in the reception of external sensory qualities (or sensible forms) in the sensorium. This idea is repeated in many forms in contemporary philosophy, including, with regard to vision, in the idea (still not firmly rejected) that the retinal image consists of points of colour. In fact, this is false. Colour is a quality that is constructed by the visual system, and though it is possible to be a realist about colour, it is completely misleading to (...) think of it as received by the retina. Moreover, such supposedly “charitable” interpretations of Aristotle’s doctrines, based on miscon- ceptions of perception-science, distort our understanding of his historical context. (shrink)

We perceive in many ways. But several dubious presuppositions about the senses mask this diversity of perception. Philosophers, scientists, and engineers alike too often presuppose that the senses (vision, audition, etc.) are independent sources of information, perception being a sum of these independent contributions. We too often presuppose that we can generalize from vision to other senses. We too often presuppose that vision itself is best understood as a passive receptacle for an image thrown by a lens. In this essay (...) we illustrate how reflection on results from the cognitive sciences undermine these (and many other) traditional presuppositions. Our illustration situates the remaining essays in the volume, Perception and its Modalities, which further extend the case against various traditional presuppositions, and offer alternatives ways to understand the senses and their role in perception. While many of the essays in this volume represent competing views and draw on different fields, from conceptual analysis to engineering, most contributors believe that to understand perception properly, we need to treat as foundational the idea that the senses work together. From that agreement, new paradigms for theorizing about perception begin to emerge. (shrink)

In this essay, I’ll argue, first, that an art object's aesthetic value (or merit) depends not just on its intrinsic properties, but on the response it evokes from a consumer who shares the producer's cultural background. My question is: what is the role of culture in relation to this response? I offer a new account of aesthetic pleasure that answers this question. On this account, aesthetic pleasure is not just a “feeling” or “sensation” that results from engaging with a work (...) of art. It is rather a mental state that facilitates engagement with an artwork, and (in the long run) enables a consumer to learn how to maximize this kind of pleasure. This is where culture comes in. If you belong to a culture, you know how to engage pleasurably with an artwork that is produced so you can engage with it in just this way. The aesthetic value of an artwork is that it plays into such a culture-pleasure nexus. -/- . (shrink)

How, and why, does Earth (the element) move to the centre of Aristotle's Universe? In this paper, I argue that we cannot understand why it does so by reference merely to the nature of Earth, or the attractive force of the Centre. Rather, we have to understand the role that Earth plays in the cosmic order. Thus, in Aristotle, the behaviour of the elements is explained as one explains the function of organisms in a living organism.

Higher animals need to identify and track material objects because they depend on interactions with them for nutrition, reproduction, and social interaction. This paper investigates the perception of material objects. It argues, first, that material objects are tagged, in all five external senses, as bearers of the features detected by them. This happens through a perceptual process, here entitled Generalized Completion, which creates the appearance of objects that have properties that transcend the activation of sensory receptors. The paper shows, secondly, (...) that material objects are privileged subjects for perceived motion and interaction. That is, they are perceived as subjects for these properties while their parts seem to be subjects only derivatively. Material objects are the only perceptual subjects that are both multisensory and privileged. (shrink)

Listening effort helps explain why people who are hard of hearing are prone to fatigue and social withdrawal. However, a one-factor model that cites only effort due to hardness of hearing is insufficient as there are many who lead happy lives despite their disability. This paper explores other contributory factors, in particular motivational arousal and pleasure. The theory of rational motivational arousal predicts that some people forego listening comprehension because they believe it to be impossible and hence worth no effort (...) at all. This is problematic. Why should the listening task be rated this way, given the availability of aids that reduce its difficulty? Two additional factors narrow the explanatory gap. First, we separate the listening task from the benefit derived as a consequence. The latter is temporally more distant, and is discounted as a result. The second factor is displeasure attributed to the listening task, which increases listening cost. Many who are hard of hearing enjoy social interaction. In such cases, the actual activity of listening is a benefit, not a cost. These people also reap the benefits of listening, but do not have to balance these against the displeasure of the task. It is suggested that if motivational harmony can be induced by training in somebody who is hard of hearing, then the obstacle to motivational arousal would be removed. This suggests a modified goal for health care professionals. Don’t just teach those who are hard of hearing how to use hearing assistance devices. Teach them how to do so with pleasure and enjoyment . (shrink)

This is the editors' Introduction to a special issue of the journal, Multisensory Research. European philosophers of the modern period found multisensory perception to be impossible because they thought that perceptual ideas are defined by how they are experienced. Under this conception, the individual modalities are determinables of ideas—just as colour is a determinable that embraces red and blue, so also the visual is a determinable that embraces colour and (visually experienced) shape. Since no idea is experienced as, for example, (...) both visual and auditory, there can be no such thing as audiovisual perception. This conception of modality is not directly contested, but a variety of perceptual phenomena are listed that could raise interesting questions if treated as multimodal in origin. (shrink)

In this article, we discuss the modularity of the emotions. In a general methodological section, we discuss the empirical basis for the postulation of modularity. Then we discuss how certain modules -- the emotions in particular -- decompose into distinct anatomical and functional parts.

Molyneux asked whether a newly sighted person could distinguish a sphere from a cube by sight alone, given that she was antecedently able to do so by touch. This, we contend, is a question about general ideas. To answer it, we must ask (a) whether spatial locations identified by touch can be identified also by sight, and (b) whether the integration of spatial locations into an idea of shape persists through changes of modality. Posed this way, Molyneux’s Question goes substantially (...) beyond question (a), about spatial locations, alone; for a positive answer to (a) leaves open whether a perceiver might cross-identify locations, but not be able to identify the shapes that collections of locations comprise. We further emphasize that MQ targets general ideas so as to distinguish it from corresponding questions about experiences of shape and about the property of tangible (vs. visual) shape. After proposing a generalized formulation of MQ, we extend earlier work (“Many Molyneux Questions,” Australasian Journal of Philosophy 2020) by showing that MQ does not admit a single answer across the board. Some integrative data-processes transfer across modalities; others do not. Seeing where and how such transfer succeeds and fails in individual cases has much to offer to our understanding of perception and its modalities. (shrink)

In this paper, I examine Aristotle's notion of potentiality as it applies to the beginning of life. Aristotle’s notion of natural kinēsis implies that we should not treat the entity at the beginning of embryonic development as human, or indeed as the same as the one that is born. This leads us to ask: When does the embryo turn into a human? Aristotle’s own answer to this question is very harsh. Bracketing the views that lead to this harsh answer, his (...) theory of kinēsis still gives us reason for searching for a replacement answer. Aristotle’s own work unfortunately gives us no help in finding this answer. (shrink)

Christopher Gauker argues that no concept can be extracted from perceptual experience and that imagistic thought cannot draw boundaries between one kind and another. Here, it is argued, on the contrary, that images have extension and are consequently Fregean concepts. Hume’s theory of abstraction as indifference is offered as an account of extra-sensory concepts. Finally, it is argued that modern theories of sensory data processing run parallel to Kant’s idea of synthesis as a pre-condition for perception.

The capacity to engage with art is a human universal present in all cultures and just about every individual human. This indicates that this capacity is evolved. In this Critical Notice of Denis Dutton's The Art Instinct, I discuss various evolutionary scenarios and their consequences. Dutton and I both reject the "spandrel" approach that originates from the work of Gould and Lewontin. Dutton proposes, following work of Geoffrey Miller, that art is sexually selected--that art-production is a sign of a fit (...) genome in males. I argue that while assortative mating may well have had a role in the evolution of "the art instinct", group selection is a better explanation. I also take issue with Dutton's "cluster concept" approach to defining art, and argue that it is a universal and essential characteristic of art that it is appreciated both for what it expresses and for the way that it expresses. It thus requires a reflexive capacity that is not operative in the appreciation of sport spectacles and pornography. (shrink)

In this Handbook entry, I review how colour similarity spaces are constructed, first for physical sources of colour and secondly for colour as it is perceptually experienced. The unique hues are features of one of the latter constructions, due initially to Hering and formalized in the Swedish Natural Colour System. I review the evidence for a physiological basis for the unique hues. Finally, I argue that Tye's realist approach to the unique hues is a mistake.

This is a short popular version of my views on aesthetic pleasure published in the online magazine, Aeon.

Mazviita Chirimuuta proposes a new “adverbialist” ontology of color. I argue that ontological disputes in the philosophy of color are uniformly terminological. Chirimuuta's proposal too is a terminological variant on others, though it has some hortatory value in directing attention to aspects of color science that have hitherto been neglected. On a side note, I also take issue with Chirimuuta's laudatory take on early modern theories of color.

Brogaard's book is extremely informative about the grammar of perceptual verbs, and questions that it indicates representationalism (as opposed to naive realism). As useful as this is, I question how much grammar tells us much about perception.

This is a comment on Frances Egan's paper, "How to Think About Mental Content." Egan distinguishes mathematical and cognitive content; she accepts the former and rejects the latter. In this comment, which was delivered at the Oberlin Colloquium in 2012, I defend cognitive content.

Perceptual content is conceptual. In this paper, some arguments against this thesis are examined and rebutted. The Richness argument, that we could not have concepts for all the colours, is queried: Doesn't the Munsell system give us such concepts? The argument that we can perceive colours and shapes without possessing the relevant concepts is rebutted: we cannot do this, but the kind of concept-possession that is relevant here is not intellectual but perceptual.

In common with many other "virtue epistemologists," Abrol Fairweather and Carlos Montemayor contend that in order to count as knowledge, a mental state must be the product of truth-apt dispositions. I question their theoretical motivations. First, I note that unlike virtue ethics, affect is irrelevant to knowledge. A generous act is arguably better if it is performed warm-heartedly, but a belief is no more creditable if it is performed with the right affect. Second, I argue that non-discursive skills are better (...) cases for virtue epistemologists than cognitive reliability—but because it is hard to know how skills work in individual instances of belief-formation, they cannot figure in the accreditation of knowledge. Finally, I argue that the oughts that attend inquiry (e.g., "you ought to look into this carefully") come from outside the context of inquiry. (shrink)

In Aristotle's cosmology, the nature of the elements is defined by their place in the Totality. Their cosmic motions keep the whole in motion, and this is their nature. Thus, the cosmos is an organized whole, a single substance directed to the good; this body constitutes together with its Prime Mover a composite substance that can be regarded as a self-mover.