Peter Carruther's Interpretive Sensory-Access (ISA) theory of self-knowledge is an interesting account of the opaqueness of our own minds that draws upon a wide range of theories from cognitive science and philosophy. In the present paper, I argue that the theory's assumptions support the conclusion that the available perceptual evidence massively underdetermines all of an agent's second-order beliefs about her own beliefs. Such a result is far more negative than the ISA's well-known pessimism regarding self-knowledge. Furthermore, I also argue that, from the same assumptions, it is possible to build an argument to the effect that cognitive scientists trying to determine an agents' true behavior-causing attitude face similar underdetermination problems. Toward the end of the paper, I suggest that the theory's problems arise from a conflation of two different ways in which terms denoting propositional attitudes, such as 'belief', are used in its formulation. Distinguishing between the two usages of these terms, in turn, leads to a further distinction between two different senses in which we can talk about the 'opaqueness' of our own minds. / Master of Arts

This dissertation analyzes the solipsism subject in Tractatus Logico-Philosophicus by Wittgenstein, exploring its possible interpretations and the result of each of them. While solipsism is held to be true and likely to match the realism, although it is not possible to be approached by the language with meaning, which is carried forward in the mystical and showed fields and where we encounter the metaphysical subject, the one that thinks, represents but does not exist as object alongside other objects. Since then, we will demonstrate that it is not possible for Wittgenstein to use the term solipsism in a usual manner, but in a different format, where it can be conceivable the me (solipsism) and the world (realism) simultaneously and in harmony, and the acceptance of other minds in the world. Thus being able to know the truth of solipsism through the mystical feeling. / A presente dissertação analisa o tema do solipsismo no Tractatus Logico-Philosophicus de Wittgenstein, explorando algumas possíveis interpretações e suas decorrências. O solipsismo é tido como verdadeiro e passível de coincidir com o realismo, mesmo não sendo possível de ser abordado pela linguagem com sentido, o que o faz transitar pelos campos do místico e do mostrável, onde nos deparamos com o sujeito metafísico, aquele que pensa, representa mas não existe como um objeto ao lado dos demais. Tentaremos mostrar não ser possível para o Wittgenstein do Tractatus fazer uso do termo solipsismo de uma forma usual, mas sim de uma forma diferenciada, onde possa ser concebível o eu (solipsismo) e o mundo (realismo) ao mesmo tempo e em harmonia, bem como a aceitação de outras mentes no mundo, podendo-se, assim, conhecer a verdade do solipsismo através do sentimento místico.