Expected Utility Theory without the Completeness Axiom

We study axiomatically the problem of obtaining an expected utility representation for a potentially incomplete preference relation over lotteries by means of a set of von Neumann-Morgenstern utility functions. It is shown that, when the prize space is a compact metric space, a preference relation admits such a multi-utility representation provided that it satisfies the standard axioms of expected utility theory. Moreover, the representing set of utilities is unique in a well-defined sense.Expected utility, incomplete preferences

Ontología y gnoseología en la Logica ingredientibus de Pedro Abelardo

El trabajo se ocupa de la sección de las Glosas a la Isagogé de Porfirio de Pedro Abelardo dedicada a las tres cuestiones sobre los universales. La parte “destructiva”, en la que Abelardo somete a crítica las doctrinas realistas de Guillermo de Champeaux no tiene un sentido meramente negativo, sino que busca llegar al punto de partida de la propia posición de Abelardo: las cosas no sólo difieren por sus formas (accidentes), sino también por sus materias (esencias). Al hablar de la imagen correspondiente al nombre universal, Abelardo no se detiene a explicar la formación del concepto universal a partir de la cosa, sino que más bien se refiere a la significación intelectual de los términos, en tanto “generan intelecciones”. Esta omisión puede explicarse por el hecho de que, para Abelardo, la inteligencia humana rara vez o nunca llega a captar las esencias de las cosas.The paper deals with the section of Peter Abaelard’s Glossae super Porphyrium concerning the three questions about the universals. The pars destruens, in which Abaelard criticizes the realistic doctrines of William of Champeaux, does not have a merely negative function, but it tries to reach the starting-point of Abaelard’s own position, namely, that things differ not only in their forms or accidents, but also in their matters or essences. When he speaks of the image of the universal term, he does not explain the process of the elaboration of the universal concept starting from the thing, but he rather refers to the intellectual signification of terms, in so far as they “produce intellections”. This default could be explained because of the fact that, in Abaelard’s view, the human intelligence hardly ever or never grasps the essences of things

Assessing the Spatial Relationship Between Fixation and Foveal Specializations

Increased cone photoreceptor density, an avascular zone (FAZ), and the displacement of inner retinal neurons to form a pit are distinct features of the human fovea. As the fovea provides the majority of our vision, appreciating how these anatomical specializations are related is important for understanding foveal development, normal visual function, and retinal disease. Here we evaluated the relationship between these specializations and their location relative to the preferred retinal locus of fixation (PRL). We measured foveal pit volume, FAZ area, peak cone density, and location of the PRL in 22 subjects with normal vision using optical coherence tomography and adaptive optics scanning light ophthalmoscopy. Foveal pit volume was positively correlated with FAZ area; however, peak cone density was not correlated with pit volume. In addition, there was no systematic offset of the location of any of these specializations relative to PRL, and there was no correlation between the magnitude of the offset from PRL and the corresponding foveal specialization measurements (pit volume, FAZ area, peak cone density). The standard deviation of our PRL measurements was consistent with previous measurements of fixational stability. These data provide insight into the sequence of events during foveal development and may have implications for visual function and retinal disease

\u3cem\u3eIn vivo\u3c/em\u3e Imaging of Human Cone Photoreceptor Inner Segments

Purpose. An often overlooked prerequisite to cone photoreceptor gene therapy development is residual photoreceptor structure that can be rescued. While advances in adaptive optics (AO) retinal imaging have recently enabled direct visualization of individual cone and rod photoreceptors in the living human retina, these techniques largely detect strongly directionally-backscattered (waveguided) light from normal intact photoreceptors. This represents a major limitation in using existing AO imaging to quantify structure of remnant cones in degenerating retina. Methods. Photoreceptor inner segment structure was assessed with a novel AO scanning light ophthalmoscopy (AOSLO) differential phase technique, that we termed nonconfocal split-detector, in two healthy subjects and four subjects with achromatopsia. Ex vivo preparations of five healthy donor eyes were analyzed for comparison of inner segment diameter to that measured in vivo with split-detector AOSLO. Results. Nonconfocal split-detector AOSLO reveals the photoreceptor inner segment with or without the presence of a waveguiding outer segment. The diameter of inner segments measured in vivo is in good agreement with histology. A substantial number of foveal and parafoveal cone photoreceptors with apparently intact inner segments were identified in patients with the inherited disease achromatopsia. Conclusions. The application of nonconfocal split-detector to emerging human gene therapy trials will improve the potential of therapeutic success, by identifying patients with sufficient retained photoreceptor structure to benefit the most from intervention. Additionally, split-detector imaging may be useful for studies of other retinal degenerations such as AMD, retinitis pigmentosa, and choroideremia where the outer segment is lost before the remainder of the photoreceptor cell

EXPECTED UTILITY THEORY WITHOUT THE COMPLETENESS AXIOM*

We study axiomatically the problem of obtaining an expected utility representation for a potentially incomplete preference relation over lotteries by means of a set of von Neumann-Morgenstern utility functions. It is shown that, when the prize space is a compact metric space, a preference relation admits such a multi-utility representation provided that it satisfies the standard axioms of expected utility theory. Moreover, the representing set of utilities is unique in a well-defined sense

De la identidad formal a la semejanza en la caracterización del conocimiento: Aristóteles y la filosofía tardomedieval

The paper deals with three outstanding Late Medieval thinkers’s repeated use of the notion of resemblance in characterizing cognition: Thomas Aquinas, Peter of John Olivi and William of Ockham. In his De anima Aristotle just uses such notion when criticizing the earlier philosophers’s opinions and makes some allusions to it when dealing with sensible perception. When it comes to intellect, resemblance is totally absent. As for Aquinas, he turns from formal identity to resemblance, as if they were coincident or interchangeable concepts. Resemblance plays a major role in his characterization of both sensation and intellection. Olivi adopts a perspective radically different as a consequence of criticizing the theory of species. As there is not any causal influx from abroad, it is the cognitive act itself which assimilates to the object. In changing his mind with respect to his earlier theory of fictum and adopting eventually a theory of mental acts, Ockham does not give up to resemblance in characterizing universal concepts. Rather, he uses resemblance in characterizing such concepts as natural signs.El artículo se ocupa del repetido uso de la noción de semejanza en la caracterización del conocimiento de tres destacados autores tardomedievales: Tomás de Aquino, Pedro de Juan Olivi y Guillermo de Ockham. En el De anima Aristóteles solo usa tal noción cuando critica las opiniones de los filósofos anteriores y hace algunas alusiones al tratar la percepción sensible. Cuando se trata del intelecto, la semejanza está totalmente ausente. En cuanto a Aquino, él hace un giro desde la identidad formal hacia la de semejanza, como si fueran conceptos coincidentes o intercambiables. La semejanza ocupa un lugar preponderante tanto en la caracterización del conocimiento sensible como en la del intelectual. Olivi adopta una perspectiva radicalmente diferente como consecuencia de su crítica a la teoría de las especies. No habiendo influjo causal desde el exterior, es el propio acto cognitivo el que se asimila al objeto. En su tránsito de la teoría del fictum a la del acto mental, Ockham no abandona la semejanza como una característica de los conceptos universales, entendidos por él como signos naturales.&nbsp

Adaptive optics imaging of inherited retinal diseases.

Adaptive optics (AO) ophthalmoscopy allows for non-invasive retinal phenotyping on a microscopic scale, thereby helping to improve our understanding of retinal diseases. An increasing number of natural history studies and ongoing/planned interventional clinical trials exploit AO ophthalmoscopy both for participant selection, stratification and monitoring treatment safety and efficacy. In this review, we briefly discuss the evolution of AO ophthalmoscopy, recent developments and its application to a broad range of inherited retinal diseases, including Stargardt disease, retinitis pigmentosa and achromatopsia. Finally, we describe the impact of this in vivo microscopic imaging on our understanding of disease pathogenesis, clinical trial design and outcome metrics, while recognising the limitation of the small cohorts reported to date

Marsilio de Padua y la teoría de la soberanía popular

Marsilius of Padua’s theory of popular sovereignty has been up to the date widely disputed. Despite the restrictiveconnotations of the concept of “weightier part” (valentior pars), the article seeks specially to point out the presence of a line of argumentation in the Defensar pacis, by means of which the universitas civium or valentior pars (insofar as they constitute the source of the legitimate political authority) are both understood in a widely inclusive sense. However, the historical projection and the political application of those theoretic concepts led, ultimately, to an emphasis on the unity and concentration of the legitimated power.La teoría de la soberanía popular de Marsilio de Padua es, hasta el día de hoy, ampliamente discutida. A pesar de las connotaciones restrictivas del concepto “parte preponderante” (valentior pars), este artículo busca, especialmente, señalar la presencia de una línea de argumentación en el Defensor pacis que presenta tanto a la universitas civium y a la valentior pars (como constituyentes de la autoridad política legítima) con un sentido ampliamente inclusivo. Sin embargo, la proyección histórica y la aplicación política de estos conceptos teóricos llevó, en última instancia, a colocar el énfasis sobre la unidad y la concentración del poder legitimado

Thomas Aquinas and the "Conditions Of Possibility" of a Natural Science: the Efficiency of Second Causes

En Summa contra gentiles III 69, Tomás de Aquino comienza una polémica con un grupo de autores que tienen en común el hecho de que “sustraen sus propias acciones de las cosas naturales”, entre ellos encontramos a algunos teólogos musulmanes (Mutakallims), Avicebron y Avicena. En todos ellos reconocemos una tendencia general a atribuir todo poder causal a Dios, al punto que no queda ningún margen de acción para los seres corpóreos. El principio general que subyace a estas doctrinas es aquel que sostiene que lo que es activo, es espiritual e inmaterial; correlativamente, lo que es corpóreo y material es entendido como más bien pasivo. Entre los inconvenientes o dificultades que derivan de estas doctrinas, Tomás señala algunos argumentos que parten de la regularidad del mundo de la experiencia y de las notas de nuestro conocimiento de la naturaleza. En esta polémica teológica contra el Ocasionalismo y el Neoplatonismo, Tomás elabora un discurso sobre las “condiciones de posibilidad” de la ciencia natural –esto es, sobre la física aristotélica–. Todo esto muestra que Tomás trata de delinear, a través de la síntesis filosóficas de fuertes diversas, una metafísica creacionista compatible con la filosofía aristotélica de la naturaleza.In Summa contra gentiles III 69, Thomas Aquinas engages in a polemic with a group of authors that have in common the fact that they “subtract their proper actions from natural things”, and among which we find some Muslim theologians (Mutakallims), Avicebron and Avicenna. In all of them we recognize a general tendency to attribute every causal power to God, to the extent that no margin of action at all is left to corporeal beings. The general principle underlying these doctrines is that what is active is spiritual and immaterial; correlatively, what is corporeal and material is regarded as rather passive. Among the inconveniences or difficulties derived from these doctrines, Aquinas points out some arguments that depart from the regularity of the world of experience and from the features of our knowledge of nature. In this theological polemic against Occasionalism and Neoplatonism, Aquinas elaborates a discourse on the “conditions of possibility” of the natural science –that is to say, the Aristotelian physics–. All this shows that Thomas tries to draw, by means of a philosophical synthesis of different sources, a creationist metaphysics compatible with the Aristotelian philosophy of nature