I aim to provide a satisfying response to radical scepticism, a view according to which our knowledge of the external world is impossible. In the first chapter I investigate into the nature and the source of scepticism. Radical scepticism is motivated both by the closureRK-based and the underdeterminationRK-based sceptical arguments. Because these two sceptical arguments are logically independent, any satisfying anti-sceptical proposal must take both of them into consideration. Also, scepticism is a paradox, albeit a spurious one, so we need to provide a diagnosis as to why we are lead into the paradox and why the alleged paradox misrepresents our epistemic standings. Hence, I advocate an obstacle-dissolving strategy for combating the sceptical problem. In chapter two, I discuss the anti-sceptical import of transcendental arguments. Although ambitious transcendental arguments are vulnerable to Stroud’s dilemma, I argue that modest transcendental arguments are promising. Modest transcendental arguments start from an undoubted psychological fact and then reveal some necessary theoretical commitments that we must make. Regarding these commitments, I submit that we are type II epistemically justified in believing them. Our commitments are type II justified in the sense that making these commitments can promote our epistemic goals, namely, the attainment of true beliefs and the avoidance of false beliefs. After that, in light of Cassam’s objection to transcendental arguments, I contend that a modest transcendental argument should be used as a stepping stone for a diagnostic anti-sceptical proposal. In chapter three, I develop a Davidsonian response to closureRK-based radical scepticism. This form of sceptical argument rests on the idea that there is no limitation on our acquisition of rationally grounded knowledge. I discuss Davidson’s theory of radical interpretation, the principle of charity and triangulation. Crucially, he argues that the content of a knowledge-apt everyday belief is determined by its typical cause and other relevant beliefs. Further, among different propositional attitudes, belief is prior to doubt. What follows is that doubt must be local because it must presume other content-determining beliefs. Also, I explore Davidson’s view on the concept of belief. On his view, in order to have a knowledge-apt belief, we must have the concept of knowledge-apt belief. We can command this concept by having the concept of objective truth. Objective truth requires that we are aware of and are capable of appreciating the possibility of a belief’s being true or false. And this possibility cannot be appreciated unless we have some related contentful beliefs to identify the content of the very belief. However, we are committed to, as opposed to believing, the proposition that the sceptical hypothesis does not obtain. It is impossible to appreciate the possibility of our fundamental commitments being false from our own perspective, because fundamental commitments specify the general cause of our beliefs. A change in this regard would cause a total change of the content of all beliefs, which leaves us no contentful belief at all to make this possibility intelligible. Therefore, the closureRK principle is not applicable to the evaluation of the sceptical hypothesis. Hence, we can retain the closureRK principle while evading the closureRK-based sceptical challenge. Unfortunately, the Davidsonian response cannot deal with the underdeterminationRK-based sceptical challenge, because we are not shown whether our rational support in the good case favours one’s everyday belief over its sceptical counterpart. In chapter four, I examine how epistemological disjunctivism can deal with underdeterminationRK-based radical scepticism. This form of sceptical argument assumes that our rational support provides at best inconclusive support for our beliefs. Therefore, a belief’s being rationally supported, no matter in the good case or in the bad case, is compatible with the belief’s being false. Epistemological disjunctivism claims that in paradigm cases of perceptual knowledge, our rational support can be both factive and reflectively accessible. The factive rational support at issue is one’s propositional seeing. I discuss both McDowell’s and Pritchard’s proposals for motivating factive seeing, and I argue for epistemological disjunctivism against three prime facie objections, i.e., the distinguishability problem, the basis problem and the access problem. When epistemological disjunctivism is shown to be a plausible view, I argue that underdeterminationRK-based radical scepticism can be dismissed. In particular, in the optimal case, factive rational support favours our everyday belief over the sceptical hypothesis. However, regarding closureRK-based radical scepticism, epistemological disjunctivism seems to licence a robust answer. The ambitious answer is that, in the good case, we can after all know the denial of the sceptical hypothesis in virtue of possessing factive rational support. And it is the immodesty of this answer that renders this response unpalatable. In the last chapter, I propose a combined treatment of the sceptical problem. Although both the Davidsonian response and the epistemological disjunctivist response can only deal with one aspect of the sceptical problem, their views are in fact mutually supportive. On the one hand, the Davidsonian response, together with a Wittgensteinian insight, shows that why rational support can only be provided in a local manner; on the other hand, epistemological disjunctivism reminds us that rational support can be factive in the good case. Putting these two points together allows us to answer the whole sceptical challenge in a uniform way. This combined proposal has three claims. First, our rational support can be both local and factive, so we can dismiss both sceptical arguments in one go. Second, the sceptical problem is a spurious paradox, so the combined treatment involves a diagnosis. This diagnosis starts from a modest transcendental argument which reveals some necessary commitments that we must make, and then proceeds to expose faulty assumptions in the sceptical paradox. Third, once the dubious assumptions are dislodged, we can evade the sceptical problem once and for all. In the end, we are offered with a satisfying response to radical scepticism.

[pt] Recentemente têm-se colocado em questão o uso do subjuntivo na Língua Portuguesa falada no Brasil. Fala-se da morte do subjuntivo, assumindo-se como fato real a hipótese de que as modalidades tradicionalmente expressas por meio do subjuntivo não estão mais sendo expressas por meio deste, ou caminhando para tal fim. O presente estudo busca desmistificar tal assunto analisando o uso de modalidades expressas pelo subjuntivo e pelo infinitivo em orações completivas regidas por verbos não factivos situados nos campos semânticos vontade e pedido/recomendação. Analisam-se, assim, não apenas estruturas em que o subjuntivo e o infinitivo são usados para expressar tais modalidades, tendo-se como critério da escolha de cada modo os sujeitos das orações principais e suas subordinadas, como também estruturas com o uso de Estruturas Alternativas (EAs) para a expressão dessas. Uma vez que tal pesquisa tem como foco a descrição de regras da língua falada, optou-se por realizar tal sistematização de acordo com a Gramática Funcional do Discurso (GDF) e se ter como objeto de estudo o português distenso falado no Brasil, ou seja, o português efetivamente falado pela classe escolarizada brasileira e usado pela mídia. Desta maneira, pode-se contribuir para uma área da descrição da Língua Portuguesa que se encontra, em geral, pouco detalhada e desatualizada em Gramáticas Tradicionais e livros de Língua Portuguesa como Língua Materna e como Segunda Língua. / [en] The use of the subjunctive in spoken Brazilian Portuguese language has been much discussed in the last decades. Much is said about the death of the subjunctive, assuming as real the hypothesis that modalities traditionally expressed by the subjunctive are no longer being expressed by this mood, or on the way. This study aims to analyze the use of modalities expressed by the subjunctive and the infinitive in complement clauses selected by non-factive verbs of the volitive and request/recommendation semantic areas. Thus, in this dissertation, we analyze not only structures in which the subjunctive and the infinitive are used to express these modalities, considering the main and the subordinate clauses subjects as a criteria for mood choice, but also clauses in which these modalities are expressed with the use of Alternative Structures. Since this research focus on spoken language rules description, we did this systematization according to the Functional Discourse Grammar (FDG) and selected as object of study the Portuguese language Brazilian educated class and media use. That way, this dissertation contributes to an area of the Brazilian Portuguese language description that, in general, needs to be detailed and updated in Traditional Grammars and Portuguese language as native or second language books.