This paper considers the use that Plato makes of the Principle of Non-Contradiction in his engagements with eristic refutations. By examining Plato’s use of the principle in his most detailed engagements with eristic—in the Sophist, the discussion of “agonistic” argumentation in the Theaetetus, and especially the Euthydemus—I aim to show that the pressure exerted on Plato by eristic refutations played a crucial role in his development of the PNC, and that the principle provided him with a much more sophisticated means (...) of demarcating philosophical argumentation from eristic than he is generally thought to have. In particular, I argue that Plato’s qualified formulation of the PNC restricts the class of genuine contradictions in such a way that reveals the contradictions that eristics produce through their refutations to be merely apparent and that Plato consistently appeals to his qualified conception of genuine contradiction in his encounters with eristics in order to demonstrate that their refutations are merely apparent. The paper concludes by suggesting that the conception of genuine contradiction afforded by the PNC did not just provide Plato with a way of demarcating genuine from eristic refutations, but also with an answer to substantive philosophical challenges that eristics raised through their refutations. (shrink)

Pretendemos neste artigo apresentar uma aproximação crítica com relação à filosofia desenvolvida pelos chamados megáricos, em face sobretudo da figura de Euclides de Mégara como representante e líder dessa linhagem de pensamento. O enfoque será feito tendo em vista o tipo de filosofia exposta e praticada por Euclides, a partir das acusações que contra ela se fizeram denunciando-a como pura erística, ou seja, a disputa e o debate entre discursos com o único objetivo de obter vitória na argumentação. O que (...) se constata em Euclides é a defesa da prática do debate com a finalidade de mostrar que o discurso é incapaz de dar conta da realidade, de um modo geral, e assim impossível de determinar, de um modo específico, o Ser e a Unidade que são a essência daquilo que organiza e move todas as coisas. Essa essência de ordem é desejável por ser boa, e o Bem se apresenta, assim, como fundamento da realidade. Os estudos sobre a tradição megárica dividem-se entre a influência dos eleatas e a influência de Sócrates. Faremos, desse modo, a defesa de que a filosofia de Euclides está afinada com o socratismo, conjugando de um modo exemplar aquilo que os eleatas haviam definido em relação ao Ser. (shrink)

The present PhD dissertation aims to examine the relation between modality and change in Aristotle’s metaphysics. -/- On the one hand, Aristotle supports his modal realism (i.e., worldly objects have modal properties - potentialities and essences - that ground the ascriptions of possibility and necessity) by arguing that the rejection of modal realism makes change inexplicable, or, worse, banishes it from the realm of reality. On the other hand, the Stagirite analyses processes by means of modal notions (‘change is the (...) actuality of what is virtual insofar as it is virtual’). In other words: to grasp what change is, one has to resort to the modal idiom of potentialities, while the fact that there is change is indicative of the fact that nature is full of modal properties. -/- Aristotle’s modal and kinetic realism finds a negative in the figure of the Megaric Diodorus Kronus. The polemical situation of Greek philosophy has indeed the dialectical advantage of not opposing the Aristotelian position to a sui generis straw man. Both in its reduction of modal judgements to temporal quantifications and in its dissolution of the reality of the state-of-being-in-motion in favour of a cinematographic view of processes, the philosophical figure of reductionist antirealism embodied by Diodorus constitutes an alternative that takes the opposite view of Aristotle’s realism. -/- The present study is structured as a discussion between these two positions. In the face of Diodorus’ antirealist challenges, Aristotle articulates modal and kinetic considerations: the answers he gives to Diodorus’ puzzles thus provide valuable insight into his metaphysics. Moreover, the examination of Aristotle’s and Diodorus’ metaphysics, because of their insight and originality, will not fail to interest the philosopher concerned with the metaphysical foundations of modern physics, insofar as the entanglement between modalities and processes is nowadays at the core of mechanics (phase spaces, path integrals, etc.). (shrink)

Este trabajo pretende elucidar los rasgos generales de la metafísica de los megáricos en contra de las interpretaciones tradicionales que les atribuyen la defensa de un monismo numérico o una teoría de las Formas. Con base en los testimonios sobre Euclides y Estilpón de Mégara, intentaré mostrar que la metafísica megárica se caracteriza principalmente por el desarrollo de los conceptos de unidad e identidad de cada cosa consigo misma, lo que conlleva el rechazo de la diferencia y, en consecuencia, de (...) cualquier tipo de cambio. Esta perspectiva no excluye la existencia de múltiples entidades que, sin embargo, no son Formas. Por esta razón, los megáricos no desarrollan un monismo de tipo numérico, sino que su visión es coherente con un monismo de tipo predicativo que impugna la posibilidad de adjudicar atributos múltiples a una misma entidad. This paper purports to clarify the general features of Megarian metaphysics against two traditional interpretations which ascribe to this philosophical group either the defense of a numerical monism or a theory of Forms. Based on the testimonies of Euclid and Stilpo of Megara, I will aim to show that a main characteristic of Megarian metaphysics is the development of the concepts of unity and identity of each thing to itself, which involves a disavowal of difference as a possible property and, consequently, of any kind of change. I also intend to show that, although this standpoint does not exclude the existence of multiple entities, it implies that these entities are not Forms. Consequently, the Megarians do not develop a numerical monism but a predicational one, according to which the adscription of many predicates to the same entity is rejected. (shrink)