Does Putnam's Argument Beg the Question against the Skeptic? Bad News for Radical Skepticism

The most convincing – and shortest – version of Putnam's argument against thepossibility of our eternal envattment is due toCrispin Wright (1994). It avoids most of themisunderstandings that have been elicited byPutnam's original presentation of the argumentin Reason, Truth and History (1981).But it is still open to the charge ofquestion-begging. True enough, the premisses ofthe argument (disquotation and externalism) canbe formulated and defended without presupposingexternal objects whose existence appearsdoubtful in the light of the very skepticalscenario which Putnam wants to repudiate.However, the argument is only valid if we add anextra premiss as to the existence of some external objects. In order to avoidcircularity, we should run the argument withexternal objects which must exist even if we arebrains in a vat, e.g. with computers rather thanwith trees. As long as the skeptic is engaged ina discussion of the brain-in-a-vat scenario, sheshould neither deny the existence of computersnor the existence of causal relations; for ifshe does, she is in fact denying that we arebrains in a vat.     

Both Random and Guided

This paper argues, first, that biological evolution can be both random and divinely guided at the same time. Next it discusses the idea that the claim that evolution is unguided is not part of the science of evolution, and defends it against a number of objections.     

Parieto-occipital areas involved in efficient filtering in search: A time course analysis of visual marking using behavioural and functional imaging procedures

Search for a colour-form conjunction target can be facilitated by presenting one set of distractors prior to the second set of distractors and the target: the preview benefit (Watson & Humphreys, 1997). The early presentation of one set of distractors enables them to be efficiently filtered from search. We report two studies investigating the time course of the preview benefit. In Experiment 1 we use a standard reaction time analysis to show that the benefit has a relatively slow time course; old items need to precede the new set by 600 ms or more in order to be fully filtered from search. Furthermore, the reductions in reaction time across time in the preview condition varied nonlinearly with the display size, suggesting that old items were discounted from search in parallel. In Experiment 2 we examined the neural locus of this filtering effect over time, using positron emission tomography (PET). We show that regions of parieto-occipital cortex are selectively activated in a preview search condition relative to a detection baseline. These regions also increase in activation as the preview interval increases (and search then becomes easier), consistent with them modulating the parallel filtering of distractors from targets in spatial search. Interestingly, the same areas as those activated in preview search were also active in conjunction search relative to its own detection baseline. Thus these regions either modulate parallel filtering in conjunction search too, or they modulate different behavioural functions according to task constraints.     

Stabilität posttraumatischer Intrusionen bei Polizeibeamten

Objectives

This prospective study examined the course of posttraumatic symptoms of police officers across a time span of 12 months (T1: directly, T2: 6 months and T3: 12 months) after confrontation with an event of potentially traumatic nature while on duty.

Method

A total of 50 police officers were diagnosed 6 months after the event (T2) using a structured interview (SCID-I and SCID-II). The global functioning was operationalized at T1 and T2 by the Global Assessment of Functioning Scale (GAF) and the degree of impairment by the Impairment Score (IS). Furthermore, the intensity of posttraumatic symptoms was assessed at T1 and T2 by the Impact of Event Scale - Revised (IES-R). After 12 months (T3) the intensity of posttraumatic symptoms of 40 police officers was assessed again by a mail enquiry.

Results

Of the police officers 14 (28%) received the diagnosis of post-traumatic stress disorder (PTSD) after 6 months. In the PTSD group a significant drop in the level of functioning and a significant increase in the degree of psychiatric impairment could be found. Concerning the stability of the intensity of posttraumatic intrusions (IES-R subscale intrusions) the PTSD group showed in comparison to the non-PTSD group a slower decrease of symptoms over the period of 12 months (ordinal interaction) and no such strong amelioration of the symptoms as for avoidance and hyperarousal could be found.

Conclusions

Although the police force are, due to pre-employment screening and the professional training, both mentally and physically healthy in comparison with the general population, the results point at the risk potential of exceptional events for police officers. Due to the fact that the intensity of posttraumatic intrusions remained on a relatively stable level it seems indispensable to render these police officers further professional support.     

How vestibular stimulation interacts with illusory hand ownership

Artificial stimulation of the peripheral vestibular system has been shown to improve ownership of body parts in neurological patients, suggesting vestibular contributions to bodily self-consciousness. Here, we investigated whether galvanic vestibular stimulation (GVS) interferes with the mechanisms underlying ownership, touch, and the localization of one’s own hand in healthy participants by using the “rubber hand illusion” paradigm. Our results show that left anodal GVS increases illusory ownership of the fake hand and illusory location of touch. We propose that these changes are due to vestibular interference with spatial and/or temporal mechanisms of visual-tactile integration leading to an enhancement of visual capture. As only left anodal GVS lead to such changes, and based on neurological data on body part ownership, we suggest that this vestibular interference is mediated by the right temporo-parietal junction and the posterior insula.     

Goethe’s Polarity of Light and Darkness

Rarely does research in the history and philosophy of science lead to new empirical results, but that is exactly what has happened in one of the essays of this special issue: Rang and Grebe-Ellis have developed new experimental techniques to perform measurements Goethe proposed 217 years ago. These measurements fit neatly with Goethe’s idea of polarity—his complementary spectrum is not only an optical, but also a thermodynamical counterpart of Newton’s spectrum. I use the new measurements, firstly, to argue against the asymmetries between light and darkness posited by Lyre and Schreiber; and, secondly, to explicate the alternative theory (the heterogeneity of darkness) that Goethe had introduced to urge scientific pluralism. In my replies to exegetical criticism by Böhler, Hampe and Zemplén, I show that the main goal of Goethe’s Farbenlehre was indeed to expose symmetries between light and darkness. Furthermore, I argue that it is worthwhile to focus on the experiments, arguments and hypotheses of the Farbenlehre, and not merely on rhetorical, narrative or stylistical aspects, as Böhler and Hampe would have it. Goethe’s criticism of Newton is often dismissed, but it is in fact surprisingly relevant today.