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Reflexões e formalizações acerca do paradoxo do exame surpresa

Quarta-feira, 10 de junho de 2009, 17h
Local: Auditório do CLE-UNICAMP

Resumo: Michel Scriven publicou em 1951 no periódico britânico de filosofia Mind um artigo em que descrevia uma determinada situação considerada paradoxal. Este paradoxo ficou conhecido como Paradoxo do Exame Surpresa. O artigo possui a seguinte sentença inicial: "A NEW AND POWERFUL PARADOX has Come to light". Desde sua publicação o artigo rendeu muitas pesquisas e comentários de importantes filósofos. As tentativas de solucionar este enigma (puzzle) são bastante divergentes umas das outras. Isso mostra que o problema relatado é mais complexo do que parece, portanto uma maior atenção deve ser dada a ele tal como O'Connor escreveu em seu artigo "It is worthwhile for philosophers to pay a little more attention to these puzzles than they have done up to now even if their scrutiny does no more than make a little clearer the ways in which ordinary language can limit and mislead us" (O'CONNOR. Pragmatic Paradoxes). O presente seminário tem como objetivo apresentar, discutir e revisar versões, comentários e análises sobre o paradoxo do enforcado ou, como é mais conhecido, o paradoxo do exame surpresa.



Referências:





Chapman JM, Butler RJ. One Quine's so-called paradox. Mind 74 1965 pp. 424-425



Fitch F. A Gödelized formulation of the prediction paradox. American Philosophical Quarterly 1 1964 pp. 161-16



Gardner M. A new prediction paradox. British Journal for the Philosophy of Science 13 1962 p. 51



Gardner, M. The Unexpected Hanging and Other Mathematical Diversions, University Of Chicago Press; Reprint edition; 1991.



O'Connor DJ. Pragmatic Paradoxes. Mind 57 1948 pp. 358-359



O'Connor DJ. Pragmatic paradoxes and fugitive propositions. Mind 60 1951 pp. 536-538



Shaw R. The paradox of the unexpected examination. Mind 67 1958 pp. 382-384

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Algebraic Semantics for modal logics





Por Samir Gorsky

In XX century we had a considerable advance on the understanding of the formal meaning of modalities. The Jónsson, McKinsey and Tarski works in fourties enabled the construction of the results of algebraic completeness for the modal systems. In fifties Kripke proposed a interesting semantic for these systems. Such semantics, today known as possible world's semantics, or Kripke's semantics, caused a great impact in the context of analytical philosophy. Articles written by Lemmon in the decade of 60 are supposed to present a synthesis of these two semantics, the algebraic semantic and the possible world's semantic. One interesting result shown in these articles is that the semantic completeness can be inferred from algebraic results through a central theorem. One of the most surprising and interesting results in the paper of Lemmon is the theorem of representation for modal algebras. This theorem of representation for the modal algebra is as a result the connection between the point of view and algebraic point of view of the semantics of possible worlds (or Kripke's semantics). The initial objective of the present work was to extend this same result for algebraic systems of Class Gmnpq proposed by Lemmon and Scott in the ``Lemmon notes''. We argue that the algebraic semantic for modal logic can serve as a basis for answers to the various criticisms directed to the development of modal logic. We'll show, finally, that the algebraic semantics, as a semantics that does not use the concept of possible worlds, may be deemed useful by supporters of modal antirealism.


References



[Carnielli e Coniglio 2003] CARNIELLI, Walter Alexandre; CONIGLIO, M. E. Splitting Logics. In: Serguei Artemov; Howard Barringer; Artur Garcez; Luis Lamb; John Woods. (Org.). We Will Show Them! Essays in Honour of Dov Gabbay. 1 ed. Londres: College Publications, 2005, v. 1, p. 389-414.


[Carnielli e Pizzi 2000] CARNIELLI, A. e PIZZI, C. Modalitá e Multimodalitá, (Milão 2000).


[Goldblatt 1976] GOLDBLATT. R.I.. Metamathematics of modal logic. Reports on Mathematical. Logic, 6:4177, 1976.


[Halmos 1955] HALMOS. P.R. Algebraic logic. Compositio Mathematica, 12:217249, 1955.


[Kripke 1959a] KRIPKE. Saul A. Semantic analysis of modal logic (abstract). The Journal of Symbolic Logic, 24:323324, 1959.


[Kripke 1959b] KRIPKE. Saul A. A completeness theorem in modal logic. The Journal of Symbolic Logic, 24:114, 1959.


[Kripke 1963] KRIPKE. Saul A. Semantical analysis of modal logic I. Normal modal prepositional calculi. Zeitschrift für Mathematische Logik und Grundlagen der Mathematik, 9:6796, 1963.


[Lemmon 1960] LEMMON, E. J. Extension Algebra and the Modal System T. In Notre Dame Journal of Formal Logic, Vol. 1 (1960), pp. 3-12.


[Lemmon 1966] LEMMON, E. J. Algebraic semantics for modal logics I and II. The Journal of symbolic logic. Vol. 31, Number 1, June 1965. Volume 31, Number 2, June 1966.


[Lemmon 1977] LEMMON. E. J. An Introduction to Modal Logic, volume 11 of American Philosophical Quarterly Monograph Series. Basil Blackwell, Oxford, 1977. Written in collaboration with Dana Scott. Edited by Krister Segerberg.


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Foto ontológica


Bertrand Russell sentado em protesto junto ao "committee of 100". (Contra as armas nucleares)




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Nova página pessoal

http://samirgorsky.vilabol.uol.com.br/index.htm

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Obituary: Peter Alexander

A philosopher focused on how we perceive and explain the world

Andrew Pyle
The Guardian, Tuesday 9 May 2006
Article history

Fonte: http://www.guardian.co.uk/news/2006/may/09/guardianobituaries.highereducation

For a quarter of a century, the philosopher Professor Peter Alexander, who has died aged 89, did outstanding work at Bristol University, both as a teacher and a researcher. While his interests were varied, he focused on two particular aspects of how we apprehend the world.
His first major concern was the nature of scientific explanation. The prevailing orthodoxy in the philosophy of science of the 1950s and 60s was logical positivism, a school that derived its account of science from the sensationalism of Ernst Mach. Such philosophers either rejected explanation outright as a goal for science, arguing that it offers only an economical redescription of the phenomena, or sought to explain explanation as no more than deduction from established empirical generalisations, as in the famous "deductive-nomological" model of Carl Hempel.
Alexander sought both to understand the sources of this conception of science and to show its inadequacy. He wrote a series of important articles (on Duhem, Hertz, Mach, Pearson, Poincaré, conventionalism and sensationalism) for Paul Edwards' great Encyclopedia of Philosophy (1967) and contributed a chapter on Philosophy of Science, 1850-1910, to DJ O'Connor's History of Western Philosophy (1964).
In his first book, Sensationalism and Scientific Explanation (1963), Alexander attacked the sensationalist's account of science as failing to do justice to the crucial explanatory role played by theory (and thus very often by the postulation of unobservable theoretical entities) in scientific explanations worthy of the name. Alexander's work thus made a contribution to the decline of the positivist orthodoxy in the philosophy of science and its replacement by the doctrines of scientific realism, in which inference to the best explanation plays a crucial role.
In the 1970s, Alexander's attention turned to the philosophy of John Locke. At that time, a strange parody of Locke's views (largely derived from George Berkeley's often unfair criticisms) was taught to students, who were left with the impression that Locke held an inconsistent and muddled sort of semi-empiricism, hardly worthy of serious philosophical engagement. Returning to the text of Locke's Essay Concerning Human Understanding, Alexander became convinced that Locke's views on many topics had been seriously misrepresented, and were far more coherent and defensible than generally reported. In a series of important papers Alexander proceeded to set the record straight.
On the distinction between primary and secondary qualities, Locke is generally represented as having characterised such qualities as red, hot and sweet as secondary qualities. When they turn out to be subjective or perceiver-dependent ("in the mind", in Berkeley's notorious phrase), we have the beginnings of a slippery slope argument leading to idealism. But, Alexander reminded us, Locke consistently distinguishes qualities in bodies from ideas in the minds of perceivers. Red, hot and sweet are mind-dependent, and are therefore not secondary qualities but ideas of secondary qualities.
The secondary qualities themselves are perfectly objective powers in bodies to cause those sensations in appropriate observers. The powers are themselves grounded in objective "textures" (arrangements of corpuscles) in the bodies. This reading of Locke both sets him in his proper historical context (as a contemporary of Robert Boyle and Isaac Newton) and enables us to see the close affiliation between his views and those of later scientific realists. This argument is most fully presented in the book Ideas, Qualities and Corpuscles: Locke and Boyle on the External World (1985), now accepted as a classic in its field.
Alexander was born in Ashford, Middlesex, but was raised in Canada, returning to England in 1932 as a cabin boy on the SS Romanby. After working for some years as a laboratory assistant and assistant chemist in the food industry, he took a BSc in chemistry with physics in 1940 from the Regent Street Polytechnic, London (now part of the University of Westminster). In 1947 he graduated with a BA in special philosophy from Birkbeck College, London, before getting his first academic post in 1949 at Leeds University. In 1957 he moved to Bristol, where he was lecturer (1957-60), reader (1960-71) and professor (1971-82). He was treasurer of the Mind Association (1964-70), president of the Aristotelian Society (1984-85) and president of the British Society for the Philosophy of Science (1987-89).
In addition to his major works, Alexander wrote on a variety of other subjects: logic and humour (eg in Lewis Carroll), absolute versus relational theories of space, the nature of explanation in Freudian psychoanalytic theory, and the significance of utopian thinking in political philosophy.
Alexander was a superb teacher, both as lecturer and as tutor and supervisor. His undergraduate lectures worked on the "iceberg principle", always giving the impression of a vast reserve of learning beneath what was on public display. But it was as a postgraduate superviser that he came into his own. He read everything twice, carefully, making meticulous comments not just on content but also on grammar and presentation. He possessed, in very large measure, the rare quality of intellectual conscience, a concern for truth and accuracy that brooked no compromises. He would think nothing of spending two hours with a postgraduate student poring over the pages of Locke or Boyle -before heading off for a well-earned pint of real ale in the senior common room.
Outside philosophy, what else mattered to him? Music, beyond any doubt, was an important part of his life. His wife Caryl, who died in 1996, was a clarinetist and music teacher; his son Meyrick became a professional musician. Beneath his somewhat reserved manner, he had a great love of wit and humour, puns and paradoxes. He admired both the literary craft and the psychological insight of Henry James. And he was a devotee of real ale even before Camra came to prominence, never travelling to a conference without his Real Ale Guide.
After retiring in 1984, he remained philosophically active, giving his last formal paper at the Centre Nationale des Recherches Scientifiques in Paris in 2004, and submitting his last article to Locke Studies in 2005.
· Peter Alexander, philosopher, born January 2 1917; died March 15 2006

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