A dialogue on Zeno's paradox of Achilles and the tortoise

The five participants in this dialogue critically discuss Zeno of Elea's paradox of Achilles and the tortoise. They consider a number of solutions to and restatements of the paradox, together with their philosophical implications. Among the issues investigated include the appearance-reality distinction, Aristotle's distinction between actual and potential infinity, the concept of a continuum, Cantor's continuum hypothesis and theory of transfinite ordinals, and, as a solution to Zeno's puzzle, the distinction between infinite and indeterminate or inexhaustible divisibility.     

Framing of decisions under ambiguity

This paper reports three experiments that illustrate framing of decision problems due to Ellsberg (1961) in which probabilities are ambiguous. Although the standard Ellsberg problems often induce violations of Savage's sure-thing principle, framing of the equivalent problems in a sequential format reduces these violations. Nevertheless, this has an ironic consequence of introducing another inconsistency in the decision makers' choices: An inconsistency between the standard and sequential formulations of the Ellsberg problems.     

Distinguishing indeterminate belief from “risk-averse” preferences

I focus my discussion on the well-known Ellsberg paradox. I find good normative reasons for incorporating non-precise belief, as represented by sets of probabilities, in an Ellsberg decision model. This amounts to forgoing the completeness axiom of expected utility theory. Provided that probability sets are interpreted as genuinely indeterminate belief (as opposed to “imprecise” belief), such a model can moreover make the “Ellsberg choices” rationally permissible. Without some further element to the story, however, the model does not explain how an agent may come to have unique preferences for each of the Ellsberg options. Levi (1986, Hard choices: Decision making under unresolved conflict. Cambridge, New York: Cambridge University Press) holds that the extra element amounts to innocuous secondary “risk” or security considerations that are used to break ties when more than one option is rationally permissible. While I think a lexical choice rule of this kind is very plausible, I argue that it involves a greater break with xpected utility theory than mere violation of the ordering axiom.     

Deductivism and the Informal Fallacies

This essay proposes and defends a general thesis concerning the nature of fallacies of reasoning. These in distinctive ways are all said to be deductively invalid. More importantly, the most accurate, complete and charitable reconstructions of these species and specimens of the informal fallacies are instructive with respect to the individual character of each distinct informal fallacy. Reconstructions of the fallacies as deductive invalidities are possible in every case, if deductivism is true, which means that in every case they should be formalizable in an expressively comprehensive formal symbolic deductive logic. The general thesis is illustrated by a detailed examination of Walter Burleigh's paradox in his c. 1323 work, De Puritate Artis Logicae Tractatus Longior (Longer Treatise on the Purity of Logic), as a challenge to the deductive validity of hypothetical syllogism. The paradox has the form, ‹If I call you a swine, then I call you an animal; if I call you an animal, then I speak truly; therefore, if I call you a swine, then I speak truly'. Several solutions to the problem are considered, and the inference is exposed as an instance of the common deductive fallacy of equivocation.     

The Unbearable Uncertainty Paradox

People can be risk seeking and risk averse, but people can also be uncertainty averse: in other words, if risk is at least the possibility of an unwanted affect, then it is not only the unwanted effect that they want to avoid, it can also be the uncertainty inherent in the possibility that they wish to avoid. This uncertainty aversion can even lead to a state where someone prefers a certain outcome at all costs, even when it is the worst case. This gives rise to the following paradox: the worst case seems to be more acceptable than the state where there is still a chance that it will not materialize. We can call this the Unbearable Uncertainty Paradox. This essay provides a first conceptual sketch of this phenomenon that seems to be widespread but nevertheless does not appear to have been identified before, either by philosophers or by psychologists.     

When to think like an epistemicist

Epistemicism is the view that seemingly vague predicates are not in fact vague. Consequently, there must be a sharp boundary between a man who is bald and one who is not bald. Although such a view is often met with incredulity, my aim is to provide a defense of epistemicism in this essay. My defense, however, is backhanded: I argue that the formal commitments of epistemicism are the result of good practical reasoning, not metaphysical necessity. To get to that conclusion, I spend most of the essay arguing that using a formal system like classical logic to manage seemingly vague situations requires practical principles to mediate between the formalism and what it aims to represent.     

前瞻记忆年老化研究的自然情境和实验室情境比较

年龄—前瞻记忆矛盾现象在实验室情境和自然情境研究中普遍存在。当任务设置为日常情境时, 前瞻记忆不受年龄影响或随年龄增长而促进, 前瞻记忆成绩可能受人格、生活方式、任务材料、提示等因素的影响; 当任务是实验室情境设置时, 与年轻被试相比, 老年被试前瞻记忆成绩一般都较差, 前瞻记忆成绩可能受回溯记忆负载、线索类型和策略控制加工的需求等因素的影响。年龄-前瞻记忆矛盾现象可能来自于环境与意向的社会性特征、认知资源分配策略等方面的原因。最后, 从被试控制、任务材料的设置、动机因素的探索等方面对今后的研究提出建议和展望。     

艾滋病非刑罪化视阈下我国防控策略的伦理思考

审视我国现有法规对艾滋病防控的影响,剖析其在维护个体权益与促进公共卫生平衡中的挑战,以实证案例和艾滋病悖论为切入点,分析艾滋病刑事定罪涉及的伦理问题,提出科学、伦理和法律方面的应对策略。强调将艾滋病病毒传播作为一个公共卫生问题加以解决是最为有效的手段。在法规制定和司法实践中,应纳入科学事实和医学证据,避免过于宽泛的刑事定罪。在决策过程中,应全面考量生命伦理学原则,最大限度避免可能的交叉歧视、多重污名以及暴力伤害。此外,还应重视公共卫生视角下的补充或替代方案,确保干预措施积极有效。

     

Imitation and novelty in product development

A human stigmergy model of product development through a series of incremental novelties and imitations is obtained by observing the isomorphism between solution trees generated by groups of humans participating in online games like Foldit, self-organizing topics in online learning systems, product evolution through a combination of innovation and imitation in the cell phone industry, and social networks formed over the past 40 years in creation of the Boston biotech commons. The model incorporates two very simple rules: (1) preferential attachment, and (2) the combination of existing product designs into a single design. A computer model used to simulate the model produces product evolution networks isomorphic to observed solution trees and product evolution trees. Additionally, industries with a high degree of novelty produce a product evolution network with scale-free and betweenness centrality structure.