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. (shrink)

We examine a number of investigations of perceptual economy or, more specifically, of minimum tendencies and minimum principles in the visual perception of form, depth, and motion. A minimum tendency is a psychophysical finding that perception tends toward simplicity, as measured in accordance with a specified metric. A minimum principle is a theoretical construct imputed to the visual system to explain minimum tendencies. After examining a number of studies of perceptual economy, we embark on a systematic analysis of this notion. (...) We examine the notion that simple perceptual representations must be defined within the "geometric constraints" provided by proximal stimulation. We then take up metrics of simplicity. Any study of perceptual economy must use a metric of simplicity; the choice of metric may be seen as a matter of convention, or it may have deep theoretical and empirical implications. We evaluate several answers to the question of why the visual system might favor economical representations. Finally, we examine several accounts of the process for achieving perceptual economy, concluding that those which favor massively parallel processing are the most plausible. (shrink)

This article seeks the origin, in the theories of Ibn al-Haytham (Alhazen), Descartes, and Berkeley, of two-stage theories of spatial perception, which hold that visual perception involves both an immediate representation of the proximal stimulus in a two-dimensional ‘‘sensory core’’ and also a subsequent perception of the three dimensional world. The works of Ibn al-Haytham, Descartes, and Berkeley already frame the major theoretical options that guided visual theory into the twentieth century. The field of visual perception was the first area (...) of what we now call psychology to apply mathematics, through geometrical models as used by Euclid, Ptolemy, Ibn al-Haytham, and Descartes (among others). The article shows that Kepler’s discovery of the retinal image, which revolutionized visual anatomy and entailed fundamental changes in visual physiology, did not alter the basic structure of theories of spatial vision. These changes in visual physiology are advanced especially in Descartes' Dioptrics and his L'Homme. Berkeley develops a radically empirist theory vision, according to which visual perception of depth is learned through associative processes that rely on the sense of touch. But Descartes and Berkeley share the assertion that there is a two-dimensional sensory core that is in principle available to consciousness. They also share the observation that we don't usually perceived this core, but find depth and distance to be phenomenally immediate, a point they struggle to accommodate theoretically. If our interpretation is correct, it was not a change in the theory of the psychology of vision that engendered the idea of a sensory core, but rather the introduction of the theory into a new metaphysical context. (shrink)

'Tis true governments cannot be supported without great charge, and it is fit everyone who enjoys a share of the protection should pay out of his estate his proportion for the maintenance of it. But still it must be with his own consent, i.e., the consent of the majority giving it either by themselves or their representatives chosen by them. For if any one shall claim a power to lay and levy taxes on the people, by his own authority, and (...) without such consent of the people, he thereby invades the fundamental law of property and subverts the end of government. For what property have I in that which another may by right take when he pleases to himself. (shrink)

Imitation is said to be the sincerest form of flattery. Socially, the proposition may well be true. But in the world of ideas it is false: to the extent that two incompatible traditions use the same words or symbols to articulate different visions of legal or social organization, imitation begets confusion, not enlightenment. The effects of that confusion, moreover, are not confined to the world of ideas, but spill over into the world of politics and public affairs. Words are more (...) than tools of description: they work also as tools of persuasion and transformation. Let a term have a favorable connotation in one context, and its imitative use can mislead people into thinking that a major departure from established practice is merely the extension or updating of an old principle to deal with new circumstances. (shrink)

In this paper, I want to explore the relationship between the various forms of individual self-interest and the appropriate structures of government. I shall begin with the former, and by degrees extend the analysis to the latter. I do so in order to mount a defense of principles of limited government, private property, and individual liberty. The ordinary analysis of self-interest treats it as though it were not only a given but also a constant of human nature, and thus makes (...) few allowances for differences between persons. Yet common experience tells us that personality and behavior are as unique as fingerprints. The positive inquiry, therefore, is how we find what is constant about self-interest in a world of natural human diversity. The normative inquiry must take into account both the constant and variable features of human nature in order to determine what forms of social arrangements hold the greatest prospect of long-term social advantage. The gulf between ‘is’ and ‘ought’ must be overcome here, as it must be in all normative discourse. Yet we cannot make sensible judgments of what ought to be the case in the domain of rules unless we first have some idea of what is the case in the domain of behavior. The initial inquiry asks why self-interest is regarded as a constant of human behavior. The explanation derives more from the biological and less from the social. The powerful pressures of natural selection weed out any organisms for whom selfinterest is not the paramount consideration. (shrink)

Background Traditional top-down national regulation of internationally mobile doctors and nurses is fast being rendered obsolete by the speed of globalisation and digitisation. Here we propose a bottom-up system in which responsibility for hiring and accrediting overseas staff begins to be shared by medical employers, managers, and insurers. Discussion In this model, professional Boards would retain authority for disciplinary proceedings in response to local complaints, but would lose their present power of veto over foreign practitioners recruited by employers who have (...) independently evaluated and approved such candidates' ability. Evaluations of this kind could be facilitated by globally accessible National Registers of professional work and conduct. A decentralised system of this kind could also dispense with time-consuming national oversight of continuing professional education and license revalidation, which tasks could be replaced over time by tighter institutional audit supported by stronger powers to terminate underperforming employees. Summary Market forces based on the reputation (and, hence, financial and political viability) of employers and institutions could continue to ensure patient safety in the future, while at the same time improving both national system efficiency and international professional mobility. (shrink)

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. (shrink)

This book presents modern logic as the formalization of reasoning that needs and deserves a semantic foundation. Chapters on propositional logic; parsing propositions; and meaning, truth and reference give the reader a basis for establishing criteria that can be used to judge formalizations of ordinary language arguments. Over 120 worked examples illustrate the scope and limitations of modern logic, as analyzed in chapters on identity, quantifiers, descriptive names, and functions. The chapter on second-order logic shows how different conceptions of predicates (...) and propositions do not lead to a common basis for quantification over predicates, as they do for quantification over things. Notable for its clarity of presentation and supplemented by many exercises, this volume will be invaluable for philosophers, linguists, mathematicians, and computer scientists who wish to better understand the tools they use in formal reasoning. (shrink)

The Gestalt psychologists adopted a set of positions on mind-body issues that seem like an odd mix. They sought to combine a version of naturalism and physiological reductionism with an insistence on the reality of the phenomenal and the attribution of meanings to objects as natural characteristics. After reviewing basic positions in contemporary philosophy of mind, we examine the Gestalt position, characterizing it m terms of phenomenal realism and programmatic reductionism. We then distinguish Gestalt philosophy of mind from instrumentalism and (...) computational functionalism, and examine Gestalt attributions of meaning and value to perceived objects. Finally, we consider a metatheoretical moral from Gestalt theory, which commends the search for commensurate description of mental phenomena and their physiological counterparts. (shrink)

Twelve subjects provided shape and orientation judgments for a set of projectively equivalent, variously rotated rectangles under three viewing conditions—monoptic, dichoptic, and binocular—with and without the presence of a pattern mask. In the absence of the mask, partial constancy was exhibited under the first two conditions and near perfect constancy under the binocular condition. Orientation was discriminated. Presence of the mask produced projective shape matching and diminished orientation discrimination. It is argued that the site of masking was postchiasmal, and the (...) results are related to previous work with pattern masking of projectively equivalent ellipses. (shrink)

Errata slip inserted. Bibliography: p. 137-140.

The contributions in the book examine the historical and contemporary manifestations of organized crime, the symbiotic relationship between legitimate and ...

This book grew out of my confusion. If logic is objective how can there be so many logics? Is there one right logic, or many right ones? Is there some underlying unity that connects them? What is the significance of the mathematical theorems about logic which I've learned if they have no connection to our everyday reasoning? The answers I propose revolve around the perception that what one pays attention to in reasoning determines which logic is appropriate. The act of (...) abstracting from our reasoning in our usual language is the stepping stone from reasoned argument to logic. We cannot take this step alone, for we reason together: logic is reasoning which has some objective value. For you to understand my answers, or perhaps better, conjectures, I have retraced my steps: from the concrete to the abstract, from examples, to general theory, to further confirming examples, to reflections on the significance of the work. (shrink)

This book is dedicated to a classic presentation of the theory of computable functions in the context of the foundations of mathematics. Part I motivates the study of computability with discussions and readings about the crisis in the foundations of mathematics in the early 20th century, while presenting the basic ideas of whole number, function, proof, and real number. Part II starts with readings from Turing and Post leading to the formal theory of recursive functions. Part III presents sufficient formal (...) logic to give a full development of Gödel's incompleteness theorems. Part IV considers the significance of the technical work with a discussion of Church's Thesis and readings on the foundations of mathematics. This new edition contains the timeline "Computability and Undecidability" as well as the essay "On mathematics". (shrink)

The variety and complexity of the eight papers in this Symposium issue are evidence that immigration is a tough nut to crack both as a matter of policy and application. There is no way that any short summary can do justice to these papers, which take a variety of moral, economic, historical, and empirical approaches to some of the recurrent issues in the field, so it is best in this short issue to try to situate the problem in a general (...) classical liberal context, to show where the pressure points are most likely to appear.The initial way to approach this problem is to start with the simple proposition that the world today is divided into national territories where the practical norm is well-nigh universal: That each sovereign state has exclusive control over its own territory, which, among other things, allows it to decide which individuals are members of that state. These citizens have privileges that may be exercised, no questions asked, on such key matters as entering labor markets, owning property, voting, and otherwise participating in political affairs. All these activities may be denied or granted, at will, to any and all outsiders by the territorial sovereign.No one doubts the need for having some form of territorial control. The need to have some monopoly of force could not be achieved if the entire world, with its infinite diversity of locations and populations, were under a single sovereign. Indeed, in many cases, the divisions within a given country may be so pronounced that separation rather than aggregation is the norm. Thus, at the end of the British Raj, India split into India and Pakistan, and later Pakistan split into Pakistan and Bangladesh. Less dramatically, Czechoslovakia split into two countries, the Czech Republic and Slovakia, while the former Yugoslavia split into five nations, starting from the northwest: Slovenia, Croatia, Bosnia and Herzegovina, Serbia, and Macedonia. Clearly, these ethic differences, be they large or small, are a major obstacle to the expansion of the size of the state. And today, the territorial instinct reasserts itself as the member states of the European Union impose more restrictions on immigration.Yet at the same time, the normative foundations of this system seem elusive. There is the following deep skepticism about the importance of these borders, expressed in these essays by Jeremy Waldron and Ilya Somin, that these national boundary lines should have such a pronounced role in political economy. Michael Blake pursues this theme further by asking the extent to which classical liberals can justify exclusion through the use of violence—or is it force? The inquiry into the dominant role of territoriality can then be expanded, as by Peter Margulies, to examine all sorts of negative externalities that could be created both by easy and strict rules of admission.Taken as a whole, there is no doubt that these national barriers are a serious obstacle to the free trade in goods and services between two individuals, one inside the boundary and one outside. The general view is that these barriers block the gains from trade, which is what drives economic progress, so that ideally all tariffs and quantitative restrictions should give way to a system of free trade in which petty objections by domestic competitors of foreign firms should not dictate local policies.It should, of course, be evident that powerful conflicting forces on free trade and protectionism ebb and flow over time. It should therefore come as no surprise that the stakes are even higher where what is at stake is the movement of people across national boundaries. The loss to any given country from keeping out potential citizens can be enormous, and we see powerful political forces clamp down on open immigration, so many of these gains from trade are lost. The situation can be even more heartbreaking when the ability to leave a country exposes innocent people to imprisonment or death.So what is the explanation for so many nations closing their borders? Much of the explanation comes from old-fashioned protectionism. Your computer programmers will take the jobs of our specialists. There is all sorts of occupational licensing and other barriers to entry within a domestic economy, so there is no reason to expect that these forces will not exert even greater influence against outsiders who do not, after all, have a voice in the local economy and who, therefore, as Alex Nowrasteh, Michael Howard, and Andrew Forrester observe, have little ability to influence domestic policy even after they enter a country. In addition, as Gabriel Chin discusses, strong racial prejudices also lead to exclusions from the domestic economy. Not only are there objections in, say, the United States and much of Western Europe, of exclusion on straight racial grounds, as exemplified by Chinese exclusion acts. The force of these exclusions are also subject to political change. Thus, the Immigration Act of 1924 (the Johnson-Reed Act) was part of a white supremacist program, which gave way two decades later to a very different legal regime with the Immigration Act of 1965, which put an end to the venerable system of national-origin quotas.Yet two other reasons for exclusion are constantly at issue. Immigrants not only bring in their labor but also their families, cultures, and traditions that, in public spaces, may clash with local norms and cultures on such elementary and critical matters as to whether women should dress modestly and wear head coverings. Will freewheeling Danes and Swedes feel comfortable if large numbers of Muslims continue their traditional practices with strong barriers between men and women? There are no obvious market mechanisms that will mitigate these issues, and the situation becomes even more fraught if there are large welfare or educational costs that fall, at least in the short run, on local citizens. These are compounded by the fact that immigrants will typically gain political rights that could easily skew the balance of political power between established and newly arrived ethnic groups by altering the outcome of national and local elections. And letting people in is not just done on a simple open-borders policy. Thus, in many countries, as Lance Pritchett discusses, there is the controversial option of letting foreigners in on short-term labor visas that require them to leave after a certain period. And there are further questions about whether people should be deported if they lied on their entry applications or committed some crime while in the new country, as has occurred in the United States. The numbers of cases can be high and their complexity great, so it is fair to ask, along with Jill Family, whether some self-conscious exceptions to the Administrative Procedure Act of 1946, analogous statutes elsewhere, should be regarded as part of the new normal.It is therefore necessary to deal with the thrust and counterthrust on all these issues. It is also fair to ask whether classical liberalism has a distinctive view on these issues, or whether the combination of private gains and multidirectional externalities gives rise to empirical questions that, as always, require further reflection, even when certain situations—the major influx of illegal immigrants on the US southern border—will generate such powerful emotions that detached intellectual inquiry is ever more difficult. We cannot answer these questions, and thus offer to you a set of essays that take a stab at these difficult topics. (shrink)

With this book, Richard A. Epstein provides a spirited and systematic defense of classical liberalism against the critiques mounted against it over the past thirty years. One of the most distinguished and provocative legal scholars writing today, Epstein here explains his controversial ideas in what will quickly come to be considered one of his cornerstone works. He begins by laying out his own vision of the key principles of classical liberalism: respect for the autonomy of the individual, (...) a strong system of private property rights, the voluntary exchange of labor and possessions, and prohibitions against force or fraud. Nonetheless, he not only recognizes but insists that state coercion is crucial to safeguarding these principles of private ordering and supplying the social infrastructure on which they depend. Within this framework, Epstein then shows why limited government is much to be preferred over the modern interventionist welfare state. Many of the modern attacks on the classical liberal system seek to undermine the moral, conceptual, cognitive, and psychological foundations on which it rests. Epstein rises to this challenge by carefully rebutting each of these objections in turn. For instance, Epstein demonstrates how our inability to judge the preferences of others means we should respect their liberty of choice regarding their own lives. And he points out the flaws in behavioral economic arguments which, overlooking strong evolutionary pressures, claim that individual preferences are unstable and that people are unable to adopt rational means to achieve their own ends. Freedom, Epstein ultimately shows, depends upon a skepticism that rightly shuns making judgments about what is best for individuals, but that also avoids the relativistic trap that all judgments about our political institutions have equal worth. A brilliant defense of classical liberalism, Skepticism and Freedom will rightly be seen as an intellectual landmark. (shrink)

In a backward masking paradigm Epstein, Hatfield, and Muise (1977) found that presentation of a frontoparallel pattern mask caused the perceived shape of elliptical figures which were rotated in depth to conform to a projective shape function. The current study extended the masking function by examining the effect of a mask which was partially or wholly cotemporal with the target. The study also assessed the functional equivalence of the masking treatment and the conventional treatment for minimizing depth information. Reports (...) of perceived shape and perceived orientation were obtained under three conditions: binocular without mask, binocular with mask, monocular without mask. Under the first condition, perceived shape conformed to objective shape and perceived orientation was proportional to objective orientation. Under the latter two conditions, perceived shape was in very close agreement to projective shape and the two functions did not differ. Orientation was underestimated greatly under both conditions. We concluded that the effect of the mask on perceived shape is mediated by its effect on encoding of orientation information, although an additional effect on the subsequent stage of shape-slant integration cannot be excluded. (shrink)

A number of fairness issues and principles are developed and discussed from the context of personnel selection. It is noted that not too much attention has been paid to these issues and concerns in the past. A distinction is made between justice and fairness having to do with the procedural components and processes of selection, the nature of the information used to make selection decisions, and the resulting outcomes of the selection process. Ideas for future research and exploration are also (...) extended. (shrink)

The most popular method of incorporating time into a formal logic is based on the work of Arthur Prior. It treats tenses as operators on sentences. In this essay I show a serious problem with that approach, a confusion of scheme versus proposition, which makes any system built in that way incoherent. I will compare how other formal logics deal with the scheme versus proposition distinction and find that only for formal modal logics does the same problem arise. I then (...) compare Prior’s approach to other ways of taking time into account in formal logics. (shrink)

The inequalities of wealth and fortune form a central part of the human condition, and these over time have been a constant source of social unease. Whether they should be praised and preserved or endured or corrected is an issue that produces uniform discord. One source of this difficulty in analysis stems from the possible ways in which these persistent inequalities arise. It is easy to condemn any differences in wealth created by the victor's expropriation of the vanquished's honest toil. (...) It is far more difficult to condemn those identical differences when they are attributable to the thrift and foresight of the successful relative to the laziness or self-destructiveness of the impoverished. Furthermore, most find it morally ambiguous how best to respond to differences between persons that are the result of luck or chance, such that they do not reflect positively or negatively on either the character of those who have done well or those who have done poorly. (shrink)

I.WhatVintage ofCivilRights?In this paper I wish to compare and contrast two separate conceptions of civil rights and to argue that the older, more libertarian conception of the subject is preferable to the more widely accepted version used in the modern civil rights movement. The first conception of civil rights focuses on the question of individual capacity. The antithesis of a person with civil rights is the slave. But even if individuals are declared free, they are nonetheless denied their civil rights (...) if they are unable to own property, to enter into contracts, to make wills, to give evidence, and to sue (and be sued) in courts. With all these civil rights claims, the target of the individual grievance is the state; it has denied large classes of individuals the formal capacities that it recognized and protected in others. The Civil War was fought largely over slavery. In its aftermath, civil rights claims protecting individual capacity received explicit, if imperfect, statutory and constitutional protection. The postbellum protections didnotguarantee these rights in absolute fashion – that is, in a way that would not be susceptible to abridgment under any circumstances. Instead, civil rights were protected in what might be called a relative fashion: whatever rights of this sort were enjoyed by white citizens were to be enjoyed by the newly freed black citizens as well. (shrink)

The country's leading libertarian scholar sets forth the essential principles for a legal system that best balances individual liberty versus the common good.

Using the case of an industrial accident involving a killer robot, the author successfully combines technical and ethical concepts to present to students and professionals real-life issues that they may one day have to confront.

In Anarchy, State, and Utopia, Robert Nozick seeks to demonstrate that principles of justice in acquisition and transfer can be applied to justify the minimal state, and no state greater than the minimal state. That approach fails to acknowledge the critical role that forced exchanges play in overcoming a range of public goods and coordination problems. These ends are accomplished by taking property for which the owner is compensated in cash or in kind in an amount that leaves him better (...) off (by his own lights) than before the transaction. Forced exchanges use coercion to form the state, but the just compensation requirement guards against redistribution state imposed redistribution for collateral purposes. Once these forced exchanges are allowed to form a state, then they may be used thereafter to justify the powers of taxation and eminent domain used to support infrastructure (roads, sewers, public utilities) that neither the minimal state nor private markets can supply. Footnotesa I have benefited from comments at the workshop at the Social Sciences Division of the California Institute of Technology. My thanks to Justin Herring and Eric Murphy, The University of Chicago Law School, for their usual capable research assistance. (shrink)

The current concerns with laggard growth and income inequality have led to a widespread set of demands for more regulation and higher taxation to reverse the trend. These two approaches move matters exactly in the wrong direction. The correct response is to find ways to reduce tax burdens and barriers to entry, and to reduce the political uncertainty associated with new government measures. It may well be too late, worldwide, for a substantial rollback in the welfare state. But the current (...) proposals will only prolong the dismal results on both fronts in any arena in which they are tried. (shrink)

It is a common conceit of academic writing to insist that progress in some given area of law or political theory is hampered by hopeless confusion over the meaning of certain standard terms. My usual attitude toward such claims is one of passionate rejection. Because the English language has served us well for such a long period of time, I bring a strong presumption of distrust to any claim of the conceptual poverty of ordinary language. The persistent fears of lack (...) of understanding are in general refuted by the success of communication in ordinary life, as measured by the coordination of human behavior that language facilitates. (shrink)

MOTIVATION The constructivization of ; => D(_£^') poses several problems. For some of these the tools of MD can be modified; for others new methods will need to be established. What must we do to make a full approximation to ; * D? We ...

This article reports the effects of gender proportions on the task activity and socioemotional participation of men and women in 85 four-person, decision-making groups. The analysis focuses on the changes in the highest and lowest levels of male and female participation. Results show that role entrapment occurs for both male and female numerical minorities. Role entrapment is a function of conformity to gender expectations rather than gender-role exaggeration, and is not limited to the extreme of the token. Both men and (...) women were affected by decreased numbers, but the effects were to the advantage of the men and to the disadvantage of the women. (shrink)