Roberto Casati

In this article I assess some results that purport to show the existence of a type of 'topological perception', i.e., perceptually based classification of topological features. Striking findings about perception in insects appear to imply that (1) configural, global properties can be considered as primitive perceptual features, and (2) topological features in particular are interesting as they are amenable to formal treatment. I discuss four interrelated questions that bear on any interpretation of findings about the perception of topological properties: what exactly are topological properties, what makes them global , in what sense the quoted findings makes them primitive, and what are the hopes of a formal theory of perception based upon them. I suggest that mathematical topology is not the correct model for cognition topological properties, hence that some other formalism ought to be used—a form of “internalized topology.” However, once the principles of this type of topology are spelled out, they may not be as globalistic as one may have expected.

Holes are a good example of the sort of entity that down-to-earth philosophers would be inclined to expel from their ontological inventory. In this work we argue instead in favor of their existence and explore the consequences of this liberality—odd as they might appear. We examine the ontology of holes, their geometry, their part-whole relations, their identity and their causal role, the ways we perceive them. We distinguish three basic kinds of holes: blind hollows, perforating tunnels, and internal cavities, treating these uniformly as immaterial bodies. We develop a morphology of holes, focusing on the way a hole can be filled, and then look at the main properties of the resulting conceptual framework: holes are parasitic upon the surfaces of their hosts; holes can move, fuse into each other, split; they can be born, develop, and die. Finally, we examine how some morphological features of holes are represented in perception, including the conditions whereby we have the impression that we see, feel, or even hear a hole. The book has over 150 pictures and is completed by a formal appendix, a section with puzzles and exercises, and a extensive annotated bibliography.

Alexandre Koyré wrote that Newton and the science that followed led to a splitting of the world: on the one hand is the “world of qualities and of sensible perceptions”, on the other is the “world of quantities and of reified geometry”. A comparison between facts held true by common sense and false by the scientific image of the world (or vice versa) seems to confirm this view. But is the dichotomy a real one? Is the world of common sense really “another world” relative to the world of the natural sciences? In this paper we argue in support of a negative answer.

Some concepts, such as colour concepts or value concepts, seem to bear traces of the mind's own make-up. For instance, the character of perceptually-determined colour concepts seems in some sense derivative from the character of the visual system. Thus, it has seemed plausible to claim that the corresponding colour properties are dispositions to elicit certain visual experiences in normal observers under suitable conditions. Much the same has been suggested for value concepts. An extreme position would be that colours and values therefore are not in the world at all, they instead are mere projections that tell us more about the users of response-dependent concepts than about the world they inhabit. But even setting aside such extreme views, a number of important philosophical and psychological questions remain open. What exactly is response-dependence, and does any concept have this feature? What is the appropriate metaphysics for properties represented by response-dependent concepts, and for these concepts themselves? What determines the extension of such properties? How are we to account for knowledge expressed in terms of response-dependent concepts? What mechanisms correctly explain the origins of response-dependent concepts, and their role in representation? This volume brings together a wide range of views on these questions.

Some concepts, such as colour concepts or value concepts, seem to bear traces of the mind's own make-up. For instance, an extreme position would be that colours and values are not in the world at all, they instead are mere projections that tell us more about the users of response-dependent concepts than about the world they inhabit. But even setting aside such extreme views, a number of important philosophical and psychological questions remain open. What exactly is response-dependence, and does any concept have this feature? What is the appropriate metaphysics for properties represented by response-dependent concepts, and for these concepts themselves? What determines the extension of such properties? How are we to account for knowledge expressed in terms of response-dependent concepts? What mechanisms correctly explain the origins of response-dependent concepts, and their role in representation?

We discuss the distinction between the sensory modalities; the metaphysics of sounds; and the structure of sound space. We defend a physicalist conception of sounds, without accepting the identification of sounds with sound-waves in the medium. Sounds, we hold, are events in resonating objects. We evaluate the two main accounts of orientation in perceptual space: relationism and absolutism. We then address Strawson's problem of whether the logical space of sounds could be spatial in the full sense of the term. In the Appendix, we discuss the logic of perceptual auditory reports, and show their compatibility with our theory of sounds.

Surprise has been characterized has an emotional reaction to an upset belief having a heuristic role and playing a criterial role for belief ascription. The discussion of cases of diachronic and synchronic violations of coherence suggests that surprise plays an epistemic role and provides subjects with some sort of phenomenological access to their subpersonal doxastic states. Lack of surprise seems not to have the same epistemic power. A distinction between belief and expectation is introduced in order to account for some aspects of surprise: expectations are construed as volatile representations that tie belief to action. In the cases in which action is not involved, general, “ideological,” expectations are generate in strict connection with the context and with the possibilities of action.

The so-called "virtual world" is often described with the help of metaphors derived from ordinary discourse on perception and action. This should not be surprising, since virtual objects were partly conceived on the basis of these metaphors. Yet, it is not a given that these metaphors are appropriate; one might need to begin using different concepts and eventually to invent new ones, more appropriate to the phenomena they describe. It might even happen, as I shall show, that these new concepts will themselves be used in situations described by the discourses on perception, action and social behaviour in a way that so far seems perfectly natural, but that, in turn, might reveal itself to be entirely inadequate. One could use these new metaphors, born as they are of new practices and new usages, for the reinterpretation of the non virtual world. The subject of this piece is the metaphysics of the book. I shall look at the way in which the Web frees it from our inadequate conception of it. This emancipation, strangely, seems to involve an economic liberation.

This issue of The Monist is devoted to the metaphysics of lesser kinds, which is to say those kinds of entity that are not generally recognized as occupying a prominent position in the categorial structure of the world. Why bother? We offer two sorts of reason. The first is methodological. In mathematics, it is common practice to study certain functions (for instance) by considering limit cases: What if x = 0? What if x is larger than any assigned value? Physics, too, often studies the (idealized) initial and boundary conditions of a given system: What would happen in the case of a perfect sphere, or a perfectly black body? In the cognitive sciences, research often thrives on the analysis of cognitive errors, perceptual illusions, brain pathologies. Also in logic one can learn a lot by studying special, anomalous scenarios such as those exhibited by the paradoxes: it is unlikely that we actually find ourselves in a soritical context, or in a liar-like situation, but the fact that we might—or simply the fact that we can conceive of such a possibility—is important enough to deserve careful consideration. In short, the odd, the unfamiliar, the extra-ordinary, the limit cases are perfectly at home in scientific and more broadly intellectual discourse at various levels, where they can be fruitfully engaged in a sophisticated way (witness the existence of specific confining and managing strategies for dealing with them); and they are important precisely because they instruct us concerning the normal, the obvious, and the paradigmatic. The same goes for metaphysics, we submit. Although its major concern is, naturally, with such core entities as substances, properties, or hunks of solid matter, a lot may be learned by paying attention to those limit cases where we find ourselves dealing with entities of much lesser kinds, whether real or putative.

What are the relationships between an entity and the space at which it is located? And between a region of space and the events that take place there? What is the metaphysical structure of localization? What its modal status? This paper addresses some of these questions in an attempt to work out at least the main coordinates of the logical structure of localization. Our task is mostly taxonomic. But we also highlight some of the underlying structural features and we single out the interactions between the notion of localization and nearby notions, such as the notions of part and whole, or of necessity and possibility. A theory of localization—we argue—is needed in order to account for the basic relations between objects and space, and runs afoul a pure part-whole theory. We also provide an axiomatization of the relation of localization and examine cases of localization involving entities different from material objects.

Ordinary reasoning about space—we argue—is first and foremost reasoning about things or events located in space. Accordingly, any theory concerned with the construction of a general model of our spatial competence must be grounded on a general account of the sort of entities that may enter into the scope of the theory. Moreover, on the methodological side the emphasis on spatial entities (as opposed to purely geometrical items such as points or regions) calls for a reexamination of the conceptual categories required for this task. Building on material presented in an earlier paper, in this work we offer some examples of what this amounts to, of the difficulties involved, and of the main directions along which spatial theories should be developed so as to combine formal sophistication with some affinity with common sense.

Understanding of elementary topological equivalencies is impaired by preconceptions about the topological structure of ordinary objects, so that the equivalencies turn out to be counterintuitive. Here I will discuss some of these preconceptions, namely the dominance of gestalt properties of the visual display of the configuration, the neglect of holistic properties, the dominance of transformations the preserve metric properties over those that preserve topological properties only, the assumption that holes are objects of their own. These factors delineate an empirical research field, intuitive topology. An explanatory hypothesis for the preconceptions suggests that they are hard-wired.