Jerry Fodor has long championed the view, recently dubbed “scientific intentional realism” (Loewer and Ray, 1991, p. xiv), that “a scientifically adequate psychology will contain laws that quantify over intentional phenomena in intentional terms.” On such a view our belief/desire psychology will be “vindicated” through empirical investigation; that is, it will be shown to denote the explanatory (or causally salient) states or events in the production of thought and behavior. That intentional properties, states, or events have causal efficacy---are not (...) mere epiphenomena---is necessary for any such vindication. This paper investigates whether intentional properties can if fact ground or sustain the causal relations empirical psychology aims to reveal. I conclude that intentional properties are not amenable to such an explanatory role, and that, therefore, a different vindication of intentional description is required of the realist. (shrink)

Jerry Fodor has long championed the view, recently dubbed “scientific intentional realism” (Loewer and Ray, 1991, p. xiv), that “a scientifically adequate psychology will contain laws that quantify over intentional phenomena in intentional terms.” On such a view our belief/desire psychology will be “vindicated” through empirical investigation; that is, it will be shown to denote the explanatory (or causally salient) states or events in the production of thought and behavior. That intentional properties, states, or events have causal efficacy---are not (...) mere epiphenomena---is necessary for any such vindication. This paper investigates whether intentional properties can if fact ground or sustain the causal relations empirical psychology aims to reveal. I conclude that intentional properties are not amenable to such an explanatory role, and that, therefore, a different vindication of intentional description is required of the realist. (shrink)

Social evolution theory conventionally takes an externalist explanatory stance, treating observed cooperation as explanandum and the positive assortment of cooperative behaviour as explanans. We ask how the circumstances bringing about this positive assortment arose in the first place. Rather than merely push the explanatory problem back a step, we move from an externalist to an interactionist explanatory stance, in the spirit of Lewontin and the Niche Construction theorists. We develop a theory of ‘social niche construction’ in which (...) we consider biological entities to be both the subject and object of their own social evolution. Some important cases of the evolution of cooperation have the side-effect of causing changes in the hierarchical level at which the evolutionary process acts. This is because the traits that act to align the fitness interests of particles in a collective can also act to diminish the extent to which those particles are bearers of heritable fitness variance, while augmenting the extent to which collectives of such particles are bearers of heritable fitness variance. In this way, we can explain upward transitions in the hierarchical level at which the Darwinian machine operates in terms of particle-level selection, even though the outcome of the process is a collective-level selection regime. Our theory avoids the logical and metaphysical paradoxes faced by other attempts to explain evolutionary transitions. (shrink)

Comparisons of rival explanations or theories often involve vague appeals to explanatory power. In this paper, we dissect this metaphor by distinguishing between different dimensions of the goodness of an explanation: non-sensitivity, cognitive salience, precision, factual accuracy and degree of integration. These dimensions are partially independent and often come into conflict. Our main contribution is to go beyond simple stipulation or description by explicating why these factors are taken to be explanatory virtues. We accomplish this by using (...) the contrastive-counterfactual approach to explanation and the view of understanding as an inferential ability. By combining these perspectives, we show how the explanatory power of an explanation in a given dimension can be assessed by showing the range of answers it provides to what-if-things-had-been-different questions and the theoretical and pragmatic importance of these questions. Our account also explains intuitions linking explanation to unification or to exhibition of a mechanism. (shrink)

I argue that examining the explanatory power of the hypothesis of extended cognition (HEC) offers a fruitful approach to the problem of cognitive system demarcation. Although in the discussions on HEC it has become common to refer to considerations of explanatory power as a means for assessing the plausibility of the extended cognition approach, to date no satisfying account of explanatory power has been presented in the literature. I suggest that the currently most prominent (...) theory of explanation in the special sciences, James Woodward’s contrastive-counterfactual theory, and an account of explanatory virtues building on that theory can be used to develop a systematic picture of cognitive system demarcation in the psychological sciences. A major difference between my differential influence (DI) account and most other theories of cognitive extension is the cognitive systems pluralism implied by my approach. By examining the explanatory power of competing traditions in psychological memory research, I conclude that internalist and externalist classificatory strategies are characterized by different profiles of explanatory virtues and should often be considered as complementary rather than competing approaches. This suggests a deflationary interpretation of HEC. (shrink)

David Malament argued that Hartry Field's nominalisation program is unlikely to be able to deal with non-space-time theories such as phase-space theories. We give a specific example of such a phase-space theory and argue that this presentation of the theory delivers explanations that are not available in the classical presentation of the theory. This suggests that even if phase-space theories can be nominalised, the resulting theory will not have the explanatory power of the original. Phase-space theories thus raise (...) problems for nominalists that go beyond Malament's initial concerns. Thanks to Mark Steiner, Jens Christian Bjerring, Ben Fraser, John Mathewson, and two anonymous referees for helpful comments on an earlier draft of this paper. CiteULike Connotea Del.icio.us What's this? (shrink)

Network analysis is increasingly used to discover and represent the organization of complex systems. Focusing on examples from neuroscience in particular, I argue that whether network models explain, how they explain, and how much they explain cannot be answered for network models generally but must be answered by specifying an explanandum, by addressing how the model is applied to the system, and by specifying which kinds of relations count as explanatory.

Schupbach and Sprenger introduce a novel probabilistic approach to measuring the explanatory power that a given explanans exerts over a corresponding explanandum. Though we are sympathetic to their general approach, we argue that it does not adequately capture the way in which the causal explanatory power that c exerts on e varies with background knowledge. We then amend their approach so that it does capture this variance. Though our account of explanatory power is less (...) ambitious than Schupbach and Sprenger’s in the sense that it is limited to causal explanatory power, it is also more ambitious because we do not limit its domain to cases where c genuinely explains e. Instead, we claim that c causally explains e if and only if our account says that c explains e with some positive amount of causal explanatory power. 1Introduction 2The Logic of Explanatory Power 3Subjective and Nomic Distributions 3.1Actual degrees of belief 3.2The causal distribution 4Background Knowledge 4.1Conditionalization and colliders 4.2A helpful intervention 5Causal Explanatory Power 5.1The applicability of explanatory power 5.2Statistical relevance ≠ causal explanatory power 5.3Interventionist explanatory power 5.4E illustrated 6Conclusion. (shrink)

Schupbach and Sprenger introduce a novel probabilistic approach to measuring the explanatory power that a given explanans exerts over a corresponding explanandum. Though we are sympathetic to their general approach, we argue that it does not adequately capture the way in which the causal explanatory power that c exerts on e varies with background knowledge. We then amend their approach so that it does capture this variance. Though our account of explanatory power is less (...) ambitious than Schupbach and Sprenger’s in the sense that it is limited to causal explanatory power, it is also more ambitious because we do not limit its domain to cases where c genuinely explains e. Instead, we claim that c causally explains e if and only if our account says that c explains e with some positive amount of causal explanatory power. (shrink)

The purpose of this essay is to offer support for the substance view of persons, the philosophical anthropology defended by Patrick Lee in his essay. In order to accomplish this the author presents a brief definition of the substance view; argues that the substance view has more explanatory power in accounting for why we believe that human persons are intrinsically valuable even when they are not functioning as such, why human persons remain identical to themselves over time, and (...) why it follows from these points that the unborn are human persons; and responds to two arguments that attempt to establish the claim that the early human being is not a unified substance until at least fourteen days after conception. (shrink)

It is widely believed that deflationary truth has no explanatory power. I will argue that it does. Specifically, I will consider some objections to deflationary truth having explanatory power, and argue that they fail. The position which will emerge is that the deflationary concept of truth is analogous to the concept of an average. Scientists take averages to be explanatory, and I will argue that the concept of deflationary truth is explanatory in the same (...) way. I then argue that this deflationary _concept_ of truth motivates a theory of the _property_ of truth which is metaphysically disunified, but that this is no obstacle to explanation. This leads to a way of understanding the deflationary/substantive distinction in terms of grounding. (shrink)

The desire to minimize the number of individual new entities postulated is often referred to as quantitative parsimony. Its influence on the default hypotheses formulated by scientists seems undeniable. I argue that there is a wide class of cases for which the preference for quantitatively parsimonious hypotheses is demonstrably rational. The justification, in a nutshell, is that such hypotheses have greater explanatory power than less parsimonious alternatives. My analysis is restricted to a class of cases I shall refer (...) to as additive. Such cases involve the postulation of a collection of qualitatively identical individual objects which collectively explain some particular observed phenomenon. Especially clear examples of this sort occur in particle physics. 1 Introduction 2 Particle physics: a case study 3 Three kinds of simplicity 4 Explanatory power 5 Explanation and non-observation 6 Parsimony and scientific methodology 7 Conclusions. (shrink)

Local miracle compatibilists claim that we are sometimes able to do otherwise than we actually do, even if causal determinism obtains. When we can do otherwise, it will often be true that if we were to do otherwise, then an actual law of nature would not have been a law of nature. Nevertheless, it is a compatibilist principle that we cannot do anything that would be or cause an event that violates the laws of nature. Carl Ginet challenges this nomological (...) principle, arguing that it is not always capable of explaining our inability to do otherwise. In response to this challenge, I point out that this principle is part of a defense against the charge that local miracle compatibilists are committed to outlandish claims. Thus it is not surprising that the principle, by itself, will often fail to explain our inability to do otherwise. I then suggest that in many situations in which we are unable to do otherwise, this can be explained by the compatibilist’s analysis of ability, or his criteria for the truth of ability claims. Thus, the failure of his nomological principle to explain the falsity of certain ability claims is no strike against local miracle compatibilism. (shrink)

This article introduces and defends a probabilistic measure of the explanatory power that a particular explanans has over its explanandum. To this end, we propose several intuitive, formal conditions of adequacy for an account of explanatory power. Then, we show that these conditions are uniquely satisfied by one particular probabilistic function. We proceed to strengthen the case for this measure of explanatory power by proving several theorems, all of which show that this measure neatly (...) corresponds to our explanatory intuitions. Finally, we briefly describe some promising future projects inspired by our account. (shrink)

Metaphysical theories heavily rely on the use of primitives to which they typically appeal. I will start by examining and evaluating some traditional well-known theories and I will discuss the role of primitives in metaphysical theories in general. I will then turn to a discussion of claims of between theories that, I think, depend on equivalences of primitives, and I will explore the nature of primitives. I will then claim that almost all explanatory power of metaphysical theories comes (...) from their primitives, and so I will turn to scrutinize the notion of "power" and "explanatory". (shrink)

We respond to Stephen T. Davis’ criticism of our earlier essay, “Assessing the Resurrection Hypothesis.” We argue that the Standard Model of physics is relevant and decisive in establishing the implausibility and low explanatory power of the Resurrection hypothesis. We also argue that the laws of physics have entailments regarding God and the supernatural and, against Alvin Plantinga, that these same laws lack the proviso “no agent supernaturally interferes.” Finally, we offer Bayesian arguments for the Legend hypothesis and (...) against the Resurrection hypothesis. (shrink)

Liberalism and naturalism are the reigning orthodoxies of most faculties today, while dualism is overwhelmingly rejected. The overarching claim defended in this paper is that liberals should consider dualism more seriously than what currently seems to be the case. This claim will be defended in two stages. First, I will argue that dualism provides better resources with which to defend foundational liberal commitments to human equality and human agency than those naturalism offers. Secondly, I will argue that dualism is plausible (...) enough to be seriously considered by liberals granted that this view is friendlier to liberal commitments than naturalism is. (shrink)

All extant purely probabilistic measures of explanatory power satisfy the following technical condition: if Pr(E | H1) > Pr(E | H2) and Pr(E | ∼H1) < Pr(E | ∼H2), then H1’s explanatory power with respect to E is greater than H2’s explanatory power with respect to E. We argue that any measure satisfying this condition faces three serious problems—the Problem of Temporal Shallowness, the Problem of Negative Causal Interactions, and the Problem of Nonexplanations. We (...) further argue that many such measures face a fourth problem—the Problem of Explanatory Irrelevance. (shrink)

Recently, in attempting to account for explanatory reasoning in probabilistic terms, Bayesians have proposed several measures of the degree to which a hypothesis explains a given set of facts. These candidate measures of "explanatory power" are shown to have interesting normative interpretations and consequences. What has not yet been investigated, however, is whether any of these measures are also descriptive of people’s actual explanatory judgments. Here, I present my own experimental work investigating this question. I argue (...) that one measure in particular is an accurate descriptor of explanatory judgments. Then, I discuss some interesting implications of this result for both the epistemology and the psychology of explanatory reasoning. (shrink)

The desire to minimize the number of individual new entities postulated is often referred to as quantitative parsimony. Its influence on the default hypotheses formulated by scientists seems undeniable. I argue that there is a wide class of cases for which the preference for quantitatively parsimonious hypotheses is demonstrably rational. The justification, in a nutshell, is that such hypotheses have greater explanatory power than less parsimonious alternatives. My analysis is restricted to a class of cases I shall refer (...) to as additive. Such cases involve the postulation of a collection of qualitatively identical individual objects which collectively explain some particular observed phenomenon. Especially clear examples of this sort occur in particle physics.1Introduction2Particle physics: a case study3Three kinds of simplicity4Explanatory power5Explanation and non‐observation6Parsimony and scientific methodology7Conclusions. (shrink)

Pautz has argued that the most prominent naive realist account of hallucination—negative epistemic disjunctivism—cannot explain how hallucinations enable us to form beliefs about perceptually presented properties. He takes this as grounds to reject both negative epistemic disjunctivism and naive realism. Our aims are two: First, to show that this objection is dialectically ineffective against naive realism, and second, to draw morals from the failure of this objection for the dispute over the nature of perceptual experience at large.

Jonah N. Schupbach and Jan Sprenger and Vincenzo Crupi and Katya Tentori have recently proposed measures of explanatory power and have shown that they are characterized by certain arguably desirable conditions or axioms. I further examine the properties of these two measures, and a third measure considered by I. J. Good and Timothy McGrew . This third measure also has an axiomatic representation. I consider a simple coin-tossing example in which only the Crupi–Tentori measure does not perform well. (...) The Schupbach–Sprenger and Good–McGrew measures are based on different notions of explanatory power, but both are tenable. 1 Introduction2 Measures of Explanatory Power3 The Schupbach–Sprenger Measure4 The Crupi–Tentori Measure5 The Good–McGrew Measure6 Affirmative versus Comprehensive Explanatory Power7 Coin-Flipping Examples8 Decomposition9 Conclusion. (shrink)

I argue that phenomenal externalism is preferable to phenomenal internalism on the basis of externalism's explanatory power with respect to qualitative character. I argue that external qualities, namely, external physical properties that are qualitative independent of consciousness, are necessary to explain qualitative character, and that phenomenal externalism is best understood as accepting external qualities while phenomenal internalism is best understood as rejecting them. I build support for the claim that external qualities are necessary to explain qualitative character on (...) the basis of a model of color perception as a certain sort of information filter by which perceivers gain access to external qualities. (shrink)

1. Introduction. The papers by Hellman and Mayo offer up a rich menu of problems and proposed solutions, so there is much here for a friendly critic to fasten on. In order to bring a modicum of focus to my commentary, I shall limit my remarks to the Duhem problem and its radiations in epistemology and methodology. Both Mayo and Hellman claim to have solutions to that hoary old problem and they tout these solutions as key indicators of the (...) class='Hi'>explanatory power of their respective technical epistemologies, whether Bayesian or Neyman/Pearsonian. Like Mayo, I shall be arguing that the Bayesian treatment of Duhem's problem is no solution at all; that, indeed, it fails to grapple with the core challenges posed by the purported ambiguities of falsification. My response to Mayo's more detailed, and I think more right-headed, treatment of the Duhem problem will be more complex. While I believe that she is moving in the right direction in many respects, I think that she fails to see one key dimension of the Duhemian conundrum. Indeed, she risks solving not Duhem's problem but quite a different one. I shall gently try to encourage her to steer her way back towards the central task. (shrink)

ABSTRACTIn this paper I offer an interventionist perspective on the explanatory structure and explanatory power of dynamical models in cognitive science: I argue that some “pure” dynamical models – ones that do not refer to mechanisms at all – in cognitive science are “contextualized causal models” and that this explanatory structure gives such models genuine explanatory power. I contrast this view with several other perspectives on the explanatory power of “pure” dynamical models. (...) One of the main results is that dynamical models need not refer to underlying mechanisms in order to be explanatory. I defend and illustrate this position in terms of dynamical models of the A-not-B error in developmental psychology as elaborated by Thelen and colleagues, and dynamical models of unintentional interpersonal coordination developed by Richardson and colleagues. (shrink)

In the mid-1800s, there was much debate about the origin or 'exciting cause' of cholera. Despite much confusion surrounding the disease, the so-called miasma theory emerged as the prevalent account about cholera's cause. Going against this mainstream view, the British physician John Snow inferred several things about cholera's origin and pathology that no one else inferred. Without observing the vibrio cholerae, however,-data unavailable to Snow and his colleagues-, there was no way of settling the question of what exactly was causing (...) cholera and how, or if, it was passed on. The question then arises as to how Snow arrived at conclusions so systematically different from those of his opponents. In this paper, I want to look at Snow's reasoning in some detail, and show that there were certain principles, explanatory power in particular, that were epistemologically important to Snow in their own right. I will show that Snow himself takes explanatory power to be an epistemic property, and makes explicit links between explanatory power and confirmation. Systematically juxtaposing Snow's claims and his opponents', I will show that Snow was right to tout the explanatory power of his theory, and that his conclusions about the epistemic superiority of his theory over that of the miasmatists' were justified. (shrink)

Influential classical and recent approaches to explicate confirmation, explanation, or explanatory power define these relations or degrees between hypotheses and evidence. This holds for both deductive and Bayesian approaches. However, this neglects the role of data, which for many everyday and scientific examples cannot simply be classified as evidence. I present arguments to sharply distinguish data from evidence in Bayesian approaches. Taking into account this distinction, we can rewrite Schupbach and Sprenger’s measure of explanatory power and (...) show the strengths of this adaptation by applying it to the example of the detection of gravitational waves in physics. (shrink)

Baker argues that quantitative parsimony—the principle that hypotheses requiring fewer entities are to be preferred over their empirically equivalent rivals—is a rational methodological criterion because it maximizes explanatory power. Baker lends plausibility to his account by confronting it with the example of postulating of the neutrino in order to resolve a discrepancy in Beta decay experiments. Baker’s account is initially attractive, but I argue that its details are problematic and that it yields undesirable consequences when applied to the (...) case of astrophysical dark matter. Baker has not succeeded in showing why quantitative parsimony is a theoretical virtue. (shrink)

According to the Epistemic Theory of Mind, knowledge is part of the best overall framework for explaining behavior at the psychological level. This theory, which has become increasingly popular in recent decades, has almost always been conjoined with an invariantist theory of “knows.” In this paper, I argue that this is a mistake: the Epistemic Theory of Mind is far more explanatorily powerful when conjoined with contextualism. I conclude that if the Epistemic Theory of Mind is true, then there is (...) a powerful new reason to accept contextualism. (shrink)

Explanation is a central concept in human psychology. Drawing upon philosophical theories of explanation, psychologists have recently begun to examine the relationship between explanation, probability and causality. Our study advances this growing literature in the intersection of psychology and philosophy of science by systematically investigating how judgments of explanatory power are affected by the prior credibility of a potential explanation, the causal framing used to describe the explanation, the generalizability of the explanation, and its statistical relevance for the (...) evidence. Collectively, the results of our five experiments support the hypothesis that the prior credibility of a causal explanation plays a central role in explanatory reasoning: first, because of the presence of strong main effects on judgments of explanatory power, and second, because of the gate-keeping role it has for other factors. Highly credible explanations were not susceptible to causal framing effects. Instead, highly credible hypotheses were sensitive to the effects of factors which are usually considered relevant from a normative point of view: the generalizability of an explanation, and its statistical relevance for the evidence. These results advance current literature in the philosophy and psychology of explanation in three ways. First, they yield a more nuanced understanding of the determinants of judgments of explanatory power, and the interaction between these factors. Second, they illuminate the close relationship between prior beliefs and explanatory power. Third, they clarify the relationship between abductive and probabilistic reasoning. (shrink)

Philosophers are divided on whether the proof- or truth-theoretic approach to logic is more fruitful. The paper demonstrates the considerable explanatory power of a truth-based approach to logic by showing that and how it can provide (i) an explanatory characterization —both semantic and proof-theoretical—of logical inference, (ii) an explanatory criterion for logical constants and operators, (iii) an explanatory account of logic’s role (function) in knowledge, as well as explanations of (iv) the characteristic features of logic (...) —formality, strong modal force, generality, topic neutrality, basicness, and (quasi-)apriority, (v) the veridicality of logic and its applicability to science, (v) the normativity of logic, (vi) error, revision, and expansion in/of logic, and (vii) the relation between logic and mathematics. The high explanatory power of the truth-theoretic approach does not rule out an equal or even higher explanatory power of the proof-theoretic approach. But to the extent that the truth-theoretic approach is shown to be highly explanatory, it sets a standard for other approaches to logic, including the proof-theoretic approach. (shrink)

The present paper provides an analysis of Euler’s solutions to the Königsberg bridges problem. Euler proposes three different solutions to the problem, addressing their strengths and weaknesses along the way. I put the analysis of Euler’s paper to work in the philosophical discussion on mathematical explanations. I propose that the key ingredient to a good explanation is the degree to which it provides relevant information. Providing relevant information is based on knowledge of the structure in question, graphs in the present (...) case. I also propose computational complexity and logical strength as measures of relevant information. (shrink)

The present paper provides an analysis of Euler’s solutions to the Königsberg bridges problem. Euler proposes three different solutions to the problem, addressing their strengths and weaknesses along the way. I put the analysis of Euler’s paper to work in the philosophical discussion on mathematical explanations. I propose that the key ingredient to a good explanation is the degree to which it provides relevant information. Providing relevant information is based on knowledge of the structure in question, graphs in the present (...) case. I also propose computational complexity and logical strength as measures of relevant information. (shrink)

Changes in synaptic strength are described as a unifying hypothesis for memory formation and storage, leading philosophers to consider the ‘synaptic efficacy hypothesis’ as a paradigmatic explanation in neuroscience. Craver’s mosaic view has been influential in understanding synaptic efficacy by presenting long-term potentiation as a multi-level mechanism nested within a multi-level structure. This paper argues that the mosaic view fails to fully capture the explanatory power of the synaptic efficacy hypothesis due to assumptions about multi-level mechanisms. I present (...) an alternative approach that emphasizes the explanatory function of unification, accounting for the widespread consensus in neuroscience regarding synaptic efficacy by highlighting the stability of synaptic causal variables across different multi-level mechanisms. (shrink)

The article focuses on the unifying and explanatory power of the selective realism defended by Anjan Chakravartty. Our main aim is twofold. First, we critically analyse the purported synthesis between entity realism and structural realism offered by the author. We give reasons to think that this unification is an inconvenient marriage. In the second step, we deal with certain controversial aspects of the intended unification among three metaphysical concepts: causation, laws of nature and natural kinds. After pointing out (...) that Chakravartty’s conception of laws is a plausible view that a scientific realist might endorse, we contend, on the contrary, that the concept of natural kind is dispensable in the framework of Chakravartty’s realism. (shrink)

Pre‐play signals that cost nothing are sometimes thought to be of no significance in interactions which are not games of pure common interest. We investigate the effect of pre‐play signals in an evolutionary setting for Assurance, or Stag Hunt, games and for a Bargaining game. The evolutionary game with signals is found to have dramatically different dynamics from the same game without signals. Signals change stability properties of equilibria in the base game, create new polymorphic equilibria, and change the basins (...) of attraction of equilibria in the base game. Signals carry information at equilibrium in the case of the new polymorphic equilibria, but transient information is the basis for large changes in the magnitude of basins of attraction of equilibria in the base game. These phenomena exemplify new and important differences between evolutionary game theory and game theory based on rational choice. (shrink)

The authors' review of alternative models for reading is of great value in identifying issues and progress in the field. More emphasis should be given to distinguishing between models that offer an explanation for behavior and those that merely simulate experimental data. An analysis of a model's discrete structure can allow for comparisons of models based upon their inherent dimensionality and explanatory power.

Cognitive architectures, like programming languages, make commitments only at the implementation level and have limited explanatory power. Their universality implies that it is hard, if not impossible, to justify them in detail from finite quantities of data. It is more fruitful to focus on particular tasks such as language understanding and propose testable theories at the computational and algorithmic levels.

Daniel Ellsberg presented in Ellsberg (The Quarterly Journal of Economics 75:643–669, 1961) various examples questioning the thesis that decision making under uncertainty can be reduced to decision making under risk. These examples constitute one of the main challenges to the received view on the foundations of decision theory offered by Leonard Savage in Savage (1972). Craig Fox and Amos Tversky have, nevertheless, offered an indirect defense of Savage. They provided in Fox and Tversky (1995) an explanation of Ellsberg’s two-color problem (...) in terms of a psychological effect: ambiguity aversion . The ‘comparative ignorance’ hypothesis articulates how this effect works and explains why it is important to an understanding of the typical pattern of responses associated with Ellsberg’s two-color problem. In the first part of this article we challenge Fox and Tversky’s explanation. We present first an experiment that extends Ellsberg’s two-color problem where certain predictions of the comparative ignorance hypothesis are not confirmed. In addition the hypothesis seems unable to explain how the subjects resolve trade-offs between security and expected pay-off when vagueness is present. Ellsberg offered an explanation of the typical behavior elicited by his examples in terms of these trade-offs and in section three we offer a model of Ellsberg’s trade-offs. The model takes seriously the role of imprecise probabilities in explaining Ellsberg’s phenomenon. The so-called three-color problem was also considered in Fox and Tversky (1995). We argue that Fox and Tversky’s analysis of this case breaks a symmetry with their analysis of the two-color problem. We propose a unified treatment of both problems and we present a experiment that confirms our hypothesis. (shrink)