Three experiments are reported which show that in certain contexts subjects reject instances of the valid modus ponens and modus tollens inference form in conditional arguments. For example, when a conditional premise, such as: If she meets her friend then she will go to a play, is accompanied by a conditional containing an additional requirement: If she has enough money then she will go to a play, subjects reject the inference from the categorical premise: She meets her friend, to the (...) conclusion: She will go to a play. Other contexts suppress the conditional fallacies. The first experiment demonstrates the effects of context on conditional reasoning. The second experiment shows that the inference suppression disappears when the categorical premise refers to both of the antecedents, such as: She meets her friend and she has enough money. In this case, subjects make both the valid inferences and the fallacies, regardless of the contextual information. The third experiment establishes that when subjects are given general information about the duration of a situation in which a conditional inducement was uttered, such as: If you shout then I will shoot you, they reject both the valid inferences and the fallacies. The results suggest that the interpretation of premises plays an even more central role in reasoning than has previously been admitted. Trois expériences montrent que dans certains contextes les sujets rejettent des instances valides de modus ponens et de modus tollens dans des énoncés conditionnels. Par exemple, quand une prémisse conditionnelle comme: Si elle rencontre son ami, alors elle ira jouer, est accompagnée par une phrase contenant une condition supplémentaire: Si elle a assez d'argent, alors elle ira jouer, les sujets rejettent l'inférence liant la prémisse catégorielle: Elle rencontre son ami, à la conclusion: Elle ira jouer. D'autres contextes éliminent également les inférences conditionnelles fallacieuses. La premiére expérience démontre l'effet du contexte sur la raisonnement conditionnel. La deuxiéme expérience montre que la suppression de l'inférence disparait quand la prémisse catégorielle fait référence aux deux antécédants, comme: Elle rencontre son ami et elle a assez d'argent. Dans ce cas, les sujets font aussi bien les inférences valides et fallacieuses, quelle que soit l'information contextuelle. La troisiéme expérience établit que quand l'on donne aux sujets des informations générales à propos de la durée d'une situation dans laquelle une conditionnelle a été prononcée, comme Si tu cries, alors je te tire dessus, ils rejettent autant les inférences valides que les inférences fallacieuses. Ces résultats suggèrent que l'interprétation des prémisses joue un rŏle encore plus central dans le raisonnement que l'on admettait auparavant. (shrink)

argument fails, and the purpose of this note is to bring out that failure. The view in question which Heck calls the Hybrid Vie~istinguishes between the meanings of names and the contents of beliefs which are expressible using names. According to the Hybrid View the meaning of a name is its referent: names do not have senses. Thus (a) "George Orwell wrote 1984" means the same as (b) "Eric Blair wrote 1984". However, the Hybrid View tells a different story about (...) the beliefs one expresses when one utters (a) or (b). The content of a belief expressed using a sentence that contains a name has more to it than just the referent of the name and whatever properties the sentence ascribes to the name's referent. There is.. (shrink)

Van der Henst argues that the theory of mental models lacks a pragmatic component. He fills the gap with the notion that reasoners draw the most relevant conclusions. We agree, but argue that theories need an element of “nondeterminism.” It is often impossible to predict either what will be most relevant or which particular conclusion an individual will draw.

There are few industries in which decisions are so intently scrutinized by millions of Canadians as the healthcare industry. Each and every day important decisions concerning the funding and delivery of healthcare are made away from the clinic and in the offices of administrators and policy makers. This book is designed to assist the current and future healthcare administrator to render effective and ethical decisions. Health administration ethics functions as a bridge between business ethics and clinical ethics. This book forges (...) the essential link between the foundational concepts of ethics theories, principles, and codes and the science of decision making. It takes a case study approach and introduces a new, user-friendly decision-making model. There is currently no Canadian textbook designed to guide administration decisions within the Canadian healthcare system, making this textbook unique in the market. (shrink)

This article presents a fundamental advance in the theory of mental models as an explanation of reasoning about facts, possibilities, and probabilities. It postulates that the meanings of compound assertions, such as conditionals (if) and disjunctions (or), unlike those in logic, refer to conjunctions of epistemic possibilities that hold in default of information to the contrary. Various factors such as general knowledge can modulate these interpretations. New information can always override sentential inferences; that is, reasoning in daily life is defeasible (...) (or nonmonotonic). The theory is a dual process one: It distinguishes between intuitive inferences (based on system 1) and deliberative inferences (based on system 2). The article describes a computer implementation of the theory, including its two systems of reasoning, and it shows how the program simulates crucial predictions that evidence corroborates. It concludes with a discussion of how the theory contrasts with those based on logic or on probabilities. (shrink)

When people understand a counterfactual such as “if the flowers had been roses, the trees would have been orange trees,” they think about the conjecture, “there were roses and orange trees,” and they also think about its opposite, the presupposed facts. We test whether people think about the opposite by representing alternates, for example, “poppies and apple trees,” or whether models can contain symbols, for example, “no roses and no orange trees.” We report the discovery of an inference‐to‐alternates effect—a tendency (...) to make an affirmative inference that refers to an alternate even from a negative minor premise, for example, “there were no orange trees, therefore there were poppies.” Nine experiments show the inference‐to‐alternates effect occurs in a binary context, but not a multiple context, and for direct and indirect reference; it can be induced and reduced by prior experience with similar inferences, and it also occurs for indicative conditionals. The results have implications for theories of counterfactual conditionals, and of negation. (shrink)

We examined how people think about how things could have turned out differently after they made a decision to cooperate or not in three social interactions: the Prisoner’s dilemma (Experiment 1), the Stag Hunt dilemma (Experiment 2), and the Chicken game (Experiment 3). We found that participants who took part in the game imagined the outcome would have been different if a different decision had been made by the other player, not themselves; they did so whether the outcome was good (...) or bad for them, their own choice had been to cooperate or not, and the other player’s choice had been to cooperate or not. Participants who only read about a fictional protagonist’s game imagined changes outside the protagonist’s control (such as the other player’s decision) after a good outcome but within the protagonist’s control (such as the protagonist’s decision) after a bad outcome. The implications for theories of counterfactual thinking and moral decision-making are discussed. (shrink)

As a preliminary step to beginning to assess the usefulness of clinical vignettes to measure ethical sensitivity in undergraduate medical students, five clinical vignettes with seven to nine ethical issues each were created. The ethical issues in the vignettes were discussed and outlined by an expert panel. One randomly selected vignette was presented to first, second and third year students at the University of Toronto as part of another examination. The students were asked to list the issues presented by the (...) patient problem. Responses from 281 students were obtained. These students identified an average of 2.72 ethical issues per vignette. Each response was classified under the domains of autonomy, beneficence and justice. Comparisons were made between classes and between vignettes. There was considerable variation between classes and the responses to different vignettes seem to indicate that different vignettes measure the various domains in different ways. It does appear that the use of vignettes is one way to measure aspects of ethical sensitivity in medical students but more study is required to clarify exactly what is being measured. (shrink)

We report two Experiments to compare counterfactual thoughts about how an outcome could have been different and causal explanations about why the outcome occurred. Experiment 1 showed that people generate counterfactual thoughts more often about controllable than uncontrollable events, whereas they generate causal explanations more often about unexpected than expected events. Counterfactual thoughts focus on specific factors, whereas causal explanations focus on both general and specific factors. Experiment 2 showed that in their spontaneous counterfactual thoughts, people focus on normal events (...) just as often as exceptional events, unlike in directed counterfactual thoughts. The findings are consistent with the suggestion that counterfactual thoughts tend to focus on how a specific unwanted outcome could have been prevented, whereas causal explanations tend to provide more general causal information that enables future understanding, prediction, and intervention in a wide range of situations. (shrink)

Abstract.Antje Jackelén's Time and Eternity successfully employs the method of correlation and a close study of the question of time to enter the dialogue between science and theology. Hermeneutical attention to language is a central element of this dialogue, but we must be aware that much science is untranslatable into ordinary language; it is when we get to the bigger metaphysical assumptions of science that true dialogue begins to happen. Thus, although the method of correlation is a useful way to (...) approach this dialogue, there is not a strict equivalence in this relationship. Theology needs science more than science needs theology. In speaking of time and God we must keep in mind the relational nature of classical Christian theism, even in its most austere forms. We should not read Enlightenment ideas of God back into the classical Christian tradition or neglect the apophatic emphasis in Christian theism, which warned against assuming knowledge of the divine nature. God's relation to time always lies beyond our understanding. Studying the effects of either the Newtonian or Einsteinian concepts of time on our theological concepts should not detract our attention from the “lived time” that characterizes human experience. Consideration of the notion of time in the Madhyamaka Buddhist tradition reminds us that we cannot control the inner reality of time and that for humans time is something to be considered pragmatically. (shrink)

We report the results of two experiments that show that participants rely on both emotion and reason in moral judgments. Experiment 1 showed that when participants were primed to communicate feelings, they provided emotive justifications not only for personal dilemmas, e.g., pushing a man from a bridge that will result in his death but save the lives of five others, but also for impersonal dilemmas, e.g., hitting a switch on a runaway train that will result in the death of one (...) man but save the lives of five others; when they were primed to communicate thoughts, they provided non-emotive justifications for both personal and impersonal dilemmas. Experiment 2 showed that participants read about a protagonist's emotions more quickly when the protagonist was faced with a personal dilemma than an impersonal one, but they read about the protagonist's decision to act or not act equally quickly for personal and impersonal dilemmas. (shrink)

When people think about how a situation might have turned out differently, they tend to imagine counterfactual alternatives to their actions. We report the results of three experiments which show that people imagine alternatives to actions differently when they know about a reason for the action. The first experiment ( n = 36) compared reason - action sequences to cause - effect sequences. It showed that people do not imagine alternatives to reasons in the way they imagine alternatives to causes: (...) they imagine an alternative to an action more than an effect, and to a cause more than a reason. The second experiment ( n = 214) and the third experiment ( n = 190) both show that different sorts of reasons have different sorts of effects on how people imagine alternatives to actions. People imagine an alternative to an action (the protagonist went to a ball) less often when they know the reason for the action was an obligation (he had to participate in fundraising) compared to when they know about a weaker reason (he wanted to meet a famous violinist) or no reason. The second experiment shows the effect for a social obligation and the third experiment replicates and extends it to a health obligation. We interpret the results in terms of the possibilities that people keep in mind about actions and their reasons. (shrink)

The theory of mental models and its computer implementations have led to crucial experiments showing that no standard logic—the sentential calculus and all logics that include it—can underlie human reasoning. The theory replaces the logical concept of validity (the conclusion is true in all cases in which the premises are true) with necessity (conclusions describe no more than possibilities to which the premises refer). Many inferences are both necessary and valid. But experiments show that individuals make necessary inferences that are (...) invalid, e.g., Few people ate steak or sole; therefore, few people ate steak. Other crucial experiments show that individuals reject inferences that are not necessary but valid, e.g., He had the anesthetic or felt pain, but not both; therefore, he had the anesthetic or felt pain, or both. Nothing in logic can justify the rejection of a valid inference: a denial of its conclusion is inconsistent with its premises, and inconsistencies yield valid inferences of any conclusions whatsoever including the one denied. So inconsistencies are catastrophic in logic. In contrast, the model theory treats all inferences as defeasible (nonmonotonic), and inconsistencies have the null model, which yields only the null model in conjunction with any other premises. So inconsistences are local. Which allows truth values in natural languages to be much richer than those that occur in the semantics of standard logics; and individuals verify assertions on the basis of both facts and possibilities that did not occur. (shrink)

Semifactual thinking about what might have been the same, e.g., ''even if Philip had not chosen the chocolate ice-cream sundae, he would have developed an allergic reaction'' has been neglected compared to counterfactual thinking about what might have been different, e.g., ''if only Philip had not chosen the chocolate ice-cream sundae, he would not have developed an allergic reaction''. We report the first systematic comparison of the two sorts of thinking in two experiments. The first experiment showed that counterfactual ''if (...) only'' thoughts about an antecedent event lead people to judge the event to be more causally related to the outcome, whereas semifactual ''even if'' thoughts lead people to judge the antecedent event to be less causally related to the outcome. In addition, the experiment showed that generating counterfactual ''if only'' thoughts increases emotional reactions such as regret, whereas generating semifactual ''even if'' thoughts decreases such reactions. The second experiment, along with a replication experiment, showed that when people complete ''if only'' and ''even if'' sentence stems, they focus on different alternative antecedents to the outcome: ''if only'' thoughts focus on alternatives that would undo the outcome whereas ''even if'' thoughts focus on alternatives that would not undo it, from among a set of available alternative antecedents in which either all, some, or none would undo the outcome. The implications of the results for theories of thinking about what might have been are discussed. (shrink)

Truth and Meaning is a collection of essays on various aspects of contemporary logic. They are given to the public, the author states, in the hope that “they may be of some service to philosophers, scientists and social scientists interested in the logical and methodological foundations of their subject.” Professor Greenwood writes from the standpoint of a specialist in his field, and assumes in the reader a familiarity with the sources and the highly technical vocabulary of modern logic.

In amblyopia, abnormal visual experience during development leads to an enduring loss of visual acuity in adulthood. Physiological studies in animal models suggest that intracortical GABAergic inhibition may mediate visual deficits in amblyopia. To better understand the relationship between visual cortical γ-aminobutyric acid (GABA) and perceptual suppression in persons with amblyopia (PWA), we employed magnetic resonance spectroscopy (MRS) to quantify GABA levels in both PWA and normally-sighted persons (NSP). In the same individuals, we obtained psychophysical measures of perceptual suppression for (...) a variety of ocular configurations. In PWA, we found a robust negative correlation between the depth of amblyopia (the difference in visual acuity between the amblyopic and non-amblyopic eyes) and GABA concentration that was specific to visual cortex and was not observed in a sensorimotor cortical control region. Moreover, lower levels of visual cortical GABA were associated with weaker perceptual suppression of the fellow eye by the amblyopic eye and stronger suppression of the amblyopic eye by the fellow eye. Taken together, our findings provide evidence that intracortical GABAergic inhibition is an important component of the pathology of human amblyopia and suggest possible therapeutic interventions to restore vision in the amblyopic eye through enhancement of visual cortical GABAergic signaling in PWA. (shrink)

People judge that an individual who attempts to harm someone but fails should be blamed and punished more when they imagine how things could have turned out worse, compared to when they imagine how things could have turned out the same, or when they think only about what happened. This moral counterfactual amplification effect occurs when people believe the protagonist had no reason for the attempt to harm, and not when the protagonist had a reason, as Experiment 1 shows. It (...) occurs for intentional failed attempts to harm and also for accidental near-misses, as Experiment 2 shows, but not for failed attempts in which the harm occurs anyway by another cause, for both general judgments about the event and specific judgments about the individual's actions, as Experiments 3 and 4 show. The implications for understanding the role of counterfactual thoughts in moral judgement are discussed. (shrink)

We resolve the two problems that Hardman raises. The first problem arises from a misunderstanding: the crucial distinction is between one-model and multiple-model problems. The second problem illuminates a deeper principle: conclusions depend on the procedures for interpreting models. We describe an algorithm that obviates the problem and empirical work that reveals a new view of syllogistic reasoning.

John J. Cleary was an internationally recognised authority in ancient Greek philosophy. This volume of penetrating studies of Plato, Aristotle, and Proclus, philosophy of mathematics, and ancient theories of education, display Cleary’s range of expertise and originality of approach.

Participants acting as mock jurors made inferences about whether a person was a suspect in a murder based on an expert's testimony about the presence of objects at the crime scene and the disclosure that the testimony was true or false. Experiment 1 showed that participants made more correct inferences, and made inferences more quickly, when the truth or falsity of the expert's testimony was disclosed immediately after the testimony rather than when the disclosure was delayed. Experiment 2 showed no (...) advantage for prior disclosure over immediate disclosure. Experiment 3 showed that the pattern of inferences when there was no disclosure mirrored the pattern when it was disclosed that the expert's testimony was true rather than false. Participants made more correct inferences from true conjunctions than disjunctions, and from false disjunctions than conjunctions. We discuss the implications for theories of the mental representations and cognitive processes that underlie human reasoning. (shrink)

We examine two competing effects of beliefs on conditional inferences. The suppression effect occurs for conditionals, for example, “if she watered the plants they bloomed,” when beliefs about additional background conditions, for example, “if the sun shone they bloomed” decrease the frequency of inferences such as modus tollens (from “the plants did not bloom” to “therefore she did not water them”). In contrast, the counterfactual elevation effect occurs for counterfactual conditionals, for example, “if she had watered the plants they would (...) have bloomed,” when beliefs about the known or presupposed facts, “she did not water the plants and they did not bloom” increase the frequency of inferences such as modus tollens. We report six experiments that show that beliefs about additional conditions take precedence over beliefs about presupposed facts for counterfactuals. The modus tollens inference is suppressed for counterfactuals that contain additional conditions (Experiments 1a and 1b). The denial of the antecedent inference (from “she did not water the plants” to “therefore they did not bloom”) is suppressed for counterfactuals that contain alternatives (Experiments 2a and 2b). We report a new “switched‐suppression” effect for conditionals with negated components, for example, “if she had not watered the plants they would not have bloomed”: modus tollens is suppressed by alternatives and denial of the antecedent by additional conditions, rather than vice versa (Experiments 3a and 3b). We discuss the implications of the results for alternative theories of conditional reasoning. (shrink)