The Church–Fitch knowability paradox in the light of structural proof theory

Anti-realist epistemic conceptions of truth imply what is called the knowability principle: All truths are possibly known. The principle can be formalized in a bimodal propositional logic, with an alethic modality ${\diamondsuit}$ and an epistemic modality ${\mathcal{K}}$ , by the axiom scheme ${A \supset \diamondsuit \mathcal{K} A}$ (KP). The use of classical logic and minimal assumptions about the two modalities lead to the paradoxical conclusion that all truths are known, ${A \supset \mathcal{K} A}$ (OP). A Gentzen-style reconstruction of the Church–Fitch paradox is presented following a labelled approach to sequent calculi. First, a cut-free system for classical (resp. intuitionistic) bimodal logic is introduced as the logical basis for the Church–Fitch paradox and the relationships between ${\mathcal {K}}$ and ${\diamondsuit}$ are taken into account. Afterwards, by exploiting the structural properties of the system, in particular cut elimination, the semantic frame conditions that correspond to KP are determined and added in the form of a block of nonlogical inference rules. Within this new system for classical and intuitionistic “knowability logic”, it is possible to give a satisfactory cut-free reconstruction of the Church–Fitch derivation and to confirm that OP is only classically derivable, but neither intuitionistically derivable nor intuitionistically admissible. Finally, it is shown that in classical knowability logic, the Church–Fitch derivation is nothing else but a fallacy and does not represent a real threat for anti-realism.     

Gender differences in social cognitive determinants of exercise adoption

Gender differences in lifestyle-related mortality and morbidity suggest a need to investigate gender-specificity of health behaviour change process and factors influencing it. We tested whether changes in self-efficacy beliefs and planning, as well as the level of social support predict change in exercise. Finnish men and women, aged 50–65 years, at an increased risk for type 2 diabetes were recruited from health care centres to participate in the Good Ageing in Lahti Region (GOAL) Lifestyle Implementation Trial. Psychosocial factors were measured with questionnaires and exercise with 7-day physical activity diaries at baseline and at 3 months. At baseline, no gender differences were found in self-efficacy and planning, but men reported receiving more social support than women. At 3 months, women reported having formed more action plans for changing their exercise routines than men. Among women, increase in self-efficacy and planning predicted increase in exercise. Among men, changes in planning played a less significant role. The more salient role of planning for women than for men, and the fact that women receive less social support, may reflect life circumstances allowing less spontaneous lifestyle decisions and a lower acceptance of lifestyle changes by their social environment.     

Perceptuomotor Compatibility in Pursuit Tracking of Two-Dimensional Movements

In a previous article, we reported an investigation of visuomanual pursuit tracking of unpredictable two-dimensional targets. This article extends the study to the tracking of predictable stimuli. In both investigations, the target trajectory was elliptical. The experimental factors we varied were the orientation of the major axis of the ellipses (horizontal or vertical), the period of the movement (9.65 to 1.61 s), and the law of motion (natural vs. transformed). In the natural condition (L), the motion results from the combination of harmonic functions, as would be the case if the target were generated by a human. In the transformed (T) condition, the law of motion departs systematically from this natural model. The main results of the study are as follows: (a) Satisfactory performance is achieved only in the natural condition. Pursuit movements obey the same constraints observed in spontaneous movements. (b) Predictability affects significantly the average delay between target and pursuit. (c) Each component of the pursuit movements depends on both components of the targets. Thus, two-dimensional tracking generalizes significantly the classical one-dimensional condition. (d) The simple model developed previously to describe performance with unpredictable targets can be generalized to cover the present case as well.     

Anxious ultimatums: How anxiety disorders affect socioeconomic behaviour

Although the role of emotion in socioeconomic decision making is increasingly recognised, the impact of specific emotional disorders, such as anxiety disorders, on these decisions has been surprisingly neglected. Twenty anxious patients and twenty matched controls completed a commonly used socioeconomic task (the Ultimatum Game), in which they had to accept or reject monetary offers from other players. Anxious patients accepted significantly more unfair offers than controls. We discuss the implications of these findings in light of recent models of anxiety, in particular the importance of interpersonal factors and assertiveness in an integrated model of decision making. Finally, we were able to show that pharmacological serotonin used to treat anxious symptomatology tended to normalise decision making, further confirming and extending the role of serotonin in co-operation, prosocial behaviour, and social decision making. These results show, for the first time, a different pattern of socioeconomic behaviour in anxiety disordered patients, in addition to the known memory, attentional and emotional biases that are part of this pathological condition.     

The problem of real trauma and the future of psychoanalysis

Abstract

Contemporary psychoanalysis emphasizes the role of “real” trauma, as it is well shown by recent sociological and theoretical developments (such as Kohut's Self psychology, object relation theory, renewed interest in Ferenczi's and Sullivan's contributions, etc.). To understand more clearly these developments, the author traces again the steps laid down by Freud in building the psychoanalytic edifice. The renewed interest in the environment, in real traumas, and in the vicissitudes of object relations could be a “paradigm change” in psychoanalysis: a return to Freud's original seduction theory. This development is seen as related to the difficulties of Freud's drive theory.     

Effects of Cannabis on Neurocognitive Functioning: Recent Advances, Neurodevelopmental Influences, and Sex Differences

Decades of research have examined the effects of cannabis on neurocognition. Recent advances in this field provide us with a better understanding of how cannabis use influences neurocognition both acutely (during intoxication) and non-acutely (after acute effects subside). Evidence of problems with episodic memory is one of the most consistent findings reported; however, several other neurocognitive domains appear to be adversely affected by cannabis use under various conditions. There is significant variability in findings across studies, thus a discussion of potential moderators is increasingly relevant. The purpose of this review was to 1) provide an update on research of cannabis’ acute and non-acute effects on neurocognition, with a focus on findings since 2007 and 2) suggest and discuss how neurodevelopmental issues and sex differences may influence cannabis effects on neurocognition. Finally we discuss how future investigations may lead to better understanding of the complex interplay among cannabis, stages of neurodevelopment, and sex on neurocognitive functioning.     

Evaluating the Source of the Risks Associated with Natural Events

Within philosophy there has been little discussion of the risks associated with natural events such as earthquakes. The first objective of this paper is to demonstrate why such risks should be the subject of more sustained philosophical interest. We argue that we cannot simply apply to risks associated with natural events those insights and frameworks for moral evaluation developed in the literature considering ordinary risks, technological risks and the risks posed by anthropogenic climate change. The second objective of this paper is to identify and develop a framework for the moral evaluation of the source of the risks associated with natural events, or the actions which sustain and impact such risks. Our discussion concentrates on the ways the construction and modification of built and natural environments can alter the probability of occurrence of natural events and the character and magnitude of the impact that such events have. We then argue for the need to develop a standard of reasonable care for decisions about the built and modified natural environment, which accounts for technical and resource constraints, as well as the place of natural hazard mitigation in public policy.     

Dynamics of the ankle joint analyzed through moment-angle loops during human walking: gender and age effects

Aim of this study was to provide a non-invasive assessment of the dynamic properties of the ankle joint during human locomotion, with specific focus on the effects of gender and age. Accordingly, flexion-extension angles and moments, obtained through gait analysis, were used to generate moment–angle loops at the ankle joint in 120 healthy subjects walking at a same normalized speed. Four reproducible types of loops were identified: Typical Loops, Narrow, Large and Yielding loops. No significant changes in the slopes of the main loop phases were observed as a function of gender and age, with the exception of a relative increase in the slope of the descending phase in elderly males compared to adult females. As for the ergometric parameters, the peak ankle moment, work produced and net work along the cycle were slightly, but significantly affected, with progressively decrease in the following order: Adult Males, Adult Females, Elderly Males and Elderly Females. The evidence that only few of the quantitative aspects of moment–angle loops were affected suggests that the control strategy which regulates the biomechanical properties of the ankle joint during walking is rather robust and qualitatively consistent across genders and age.