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Closure Principle (closure + principle)
Selected AbstractsKnowability, Closure, and Anti-RealismDIALECTICA, Issue 1 2008Sven Rosenkranz In light of the paradox of knowability anti-realists ought to revise their wholesale equation of truth and knowability, lest they be committed to the absurd conclusion that there are no truths that will never be known. The task accordingly becomes to identify the problematic statements the knowability of whose truth would force that conclusion and to restrict the equation in appropriate ways to all but the problematic statements. This restriction strategy was first implemented by Tennant. However, recently Williamson and Brogaard and Salerno have argued that the restriction strategy, and in particular Tennant's implementation of it, fail to avert the paradoxical conclusion. Here I argue, first, that the arguments devised by Brogaard and Salerno are ineffective because they rely on an invalid closure principle and, second, that while Williamson's argument may suffice to undermine Tennant's specific proposal, it fails to discredit the restriction strategy as such. To this end, I give a better characterisation of the problematic cases, which is immune to Williamson's criticism, and then show how the restricted anti-realist thesis fares in light of the meaning-theoretical arguments anti-realists typically advance in support of their view. [source] A Pragmatic Dissolution of Harman's ParadoxPHILOSOPHY AND PHENOMENOLOGICAL RESEARCH, Issue 2 2007IGOR DOUVEN There is widespread agreement that we cannot know of a lottery ticket we own that it is a loser prior to the drawing of the lottery. At the same time we appear to have knowledge of events that will occur only if our ticket is a loser. Supposing any plausible closure principle for knowledge, the foregoing seems to yield a paradox. Appealing to some broadly Gricean insights, the present paper argues that this paradox is apparent only. [source] A CLOSER LOOK AT CLOSURE SCEPTICISMPROCEEDINGS OF THE ARISTOTELIAN SOCIETY (HARDBACK), Issue 1 2006Michael Blome-Tillmann ABSTRACT The paper argues that there is no valid closure principle that can be used to infer sceptical conclusions. My argument exploits the Gettier Intuition that knowledge is incompatible with accidentally true belief. This intuition is interpreted as placing a constraint on beliefs that can count as knowledge: only beliefs which are based on reasons that are relevantly linked to the beliefs' truth can qualify as knowledge. I argue that closure principles are to reflect this constraint by accommodating the requirement that a subject's belief p needs to be based on her competent derivation of p from a known q. The emerging account is finally argued to reconcile Dretske's anti-closure intuitions with the intuition that we can extend knowledge by deduction, while simultaneously blocking closure arguments for scepticism about the external world. [source] SOLVING THE PROBLEM OF EASY KNOWLEDGETHE PHILOSOPHICAL QUARTERLY, Issue 233 2008Tim Black Stewart Cohen argues that several epistemological theories fall victim to the problem of easy knowledge: they allow us to know far too easily that certain sceptical hypotheses are false and that how things seem is a reliable indicator of how they are. This problem is a result of the theories' interaction with an epistemic closure principle. Cohen suggests that the theories should be modified. I argue that attempts to solve the problem should focus on closure instead; a new and plausible epistemic closure principle can solve the problem of easy knowledge. My solution offers a uniform and more successful response to different versions of the problem of easy knowledge. [source] Modelling night-time ecosystem respiration by a constrained source optimization methodGLOBAL CHANGE BIOLOGY, Issue 2 2002Chun-Ta Lai Abstract One of the main challenges to quantifying ecosystem carbon budgets is properly quantifying the magnitude of night-time ecosystem respiration. Inverse Lagrangian dispersion analysis provides a promising approach to addressing such a problem when measured mean CO2 concentration profiles and nocturnal velocity statistics are available. An inverse method, termed ,Constrained Source Optimization' or CSO, which couples a localized near-field theory (LNF) of turbulent dispersion to respiratory sources, is developed to estimate seasonal and annual components of ecosystem respiration. A key advantage to the proposed method is that the effects of variable leaf area density on flow statistics are explicitly resolved via higher-order closure principles. In CSO, the source distribution was computed after optimizing key physiological parameters to recover the measured mean concentration profile in a least-square fashion. The proposed method was field-tested using 1 year of 30-min mean CO2 concentration and CO2 flux measurements collected within a 17-year-old (in 1999) even-aged loblolly pine (Pinus taeda L.) stand in central North Carolina. Eddy-covariance flux measurements conditioned on large friction velocity, leaf-level porometry and forest-floor respiration chamber measurements were used to assess the performance of the CSO model. The CSO approach produced reasonable estimates of ecosystem respiration, which permits estimation of ecosystem gross primary production when combined with daytime net ecosystem exchange (NEE) measurements. We employed the CSO approach in modelling annual respiration of above-ground plant components (c. 214 g C m,2 year,1) and forest floor (c. 989 g C m,2 year,1) for estimating gross primary production (c. 1800 g C m,2 year,1) with a NEE of c. 605 g C m,2 year,1 for this pine forest ecosystem. We conclude that the CSO approach can utilise routine CO2 concentration profile measurements to corroborate forest carbon balance estimates from eddy-covariance NEE and chamber-based component flux measurements. [source] A CLOSER LOOK AT CLOSURE SCEPTICISMPROCEEDINGS OF THE ARISTOTELIAN SOCIETY (HARDBACK), Issue 1 2006Michael Blome-Tillmann ABSTRACT The paper argues that there is no valid closure principle that can be used to infer sceptical conclusions. My argument exploits the Gettier Intuition that knowledge is incompatible with accidentally true belief. This intuition is interpreted as placing a constraint on beliefs that can count as knowledge: only beliefs which are based on reasons that are relevantly linked to the beliefs' truth can qualify as knowledge. I argue that closure principles are to reflect this constraint by accommodating the requirement that a subject's belief p needs to be based on her competent derivation of p from a known q. The emerging account is finally argued to reconcile Dretske's anti-closure intuitions with the intuition that we can extend knowledge by deduction, while simultaneously blocking closure arguments for scepticism about the external world. [source] Turbulent flows on forested hilly terrain: the recirculation regionTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 625 2007D. Poggi Abstract A number of analytical and numerical studies employing first-order closure principles have suggested that canopy flows on gentle sinusoidal hills feature a recirculation region, situated on the lee side, that can dramatically affect scalar transfer between the biosphere and the atmosphere. To date, the onset of this region, and its effects on bulk flow properties, have not been experimentally investigated. We study the applicability of first-order closure schemes jointly with the properties of this recirculation region, using detailed laser Doppler anemometry (LDA) measurements. These experiments are conducted in a neutrally stratified boundary-layer flow within a large flume over a train of gentle and narrow hills. The canopy is composed of an array of vertical cylinders with a frontal-area index concentrated in the upper third, to resemble a tall hardwood forest at maximum leaf area. The LDA measurements are recorded for both sparse and dense canopies. We find that, while the onset of a recirculation region is ambiguous in the sparse-canopy case, it is well delineated in the dense-canopy case. This finding constitutes the first experimental evidence confirming the analytical and numerical model predictions concerning this region in dense canopies on gentle hills. Moreover, we show that the presence of the recirculation region can explain the anomalous pressure variation across the hill (first reported in numerical simulations) using an ,effective hill shape' function. Detailed momentum-flux measurements show, surprisingly, that the effective mixing length leff within the canopy and in the inner layer is not significantly affected by the recirculation region. We expected leff to be comparable to the size of the vortex responsible for the recirculation zone, but the measurements show that leff maintains its canonical canopy turbulence shape. Using laser-induced fluorescence (LIF) measurements, we find that the recirculation region is not characterized by a classical ,rotor', but by a highly intermittent zone with alternating positive and negative velocity values in the lower layers of the canopy. These LIF measurements may explain why leff maintains its canonical canopy turbulence shape in the recirculation region. The LIF measurements also show that the main mechanism for scalar transfer within the recirculation region is a sequence of accumulation,ejection episodes that are quasi-periodic in nature. Copyright © 2007 Royal Meteorological Society [source] | ||||||||||