Approximation theory is a fundamental tool in order to study the representation theory of a ring R. Roughly speaking, it consists in determining suitable additive or abelian subcategories of the whole module category Mod-R with nice enough functorial properties. For example, torsion theory is a well suited incarnation of approximation theory. Of course, such an idea has been generalised to the additive setting itself, so that both Mod-R and other interesting categories related with R may be linked functorially. By the seminal work of Beilinson, Bernstein and Deligne (1982), the derived category of the ring turns out to admit useful torsion theories, called t-structures: they are pairs of full subcategories of D(R) whose intersection, called the heart, is always an abelian category. The so-called standard t-structure of D(R) has as its heart the module category Mod-R itself. Since then a lot of results devoted to the module theoretic characterisation of the hearts have been achieved, providing evidence of the usefulness of the t-structures in the representation theory of R. In 2020, following a research line promoted by many other authors, Saorin and Stovicek proved that the heart of any compactly generated t-structure is always a locally finitely presented Grothendieck categories (actually, this is true for any t-structure in a triangulated category with coproducts). Essentially, this means that the hearts of D(R) come equipped with a finiteness condition miming that one valid in Mod-R. In the present thesis we tackle the problem of characterising when the hearts of certain compactly generated t-structures of a commutative ring are even locally coherent. In this commutative context, after the works of Neeman and Alonso, Jeremias and Saorin, compactly generated t-structures turned out to be very interesting over a noetherian ring, for they are in bijection with the Thomason filtrations of the prime spectrum. In other words, they are classified by geometric objects, moreover their constituent subcategories have a precise cohomological description. However, if the ascending chain condition lacks, such classification is somehow partial, though provided by Hrbek. The crucial point is that the constituents of the t-structures have a different description w.r.t. that available in the noetherian setting, yet if one copies the latter for an arbitrary ring still obtains a t-structure, but it is not clear whether it must be compactly generated. Consequently, pursuing the study of the local coherence of the hearts given by a Thomason filtration, we ended by considering two t-structures. Our technique in order to face the lack of the ascending chain condition relies on a further approximation of the hearts by means of suitable torsion theories. The main results of the thesis are the following: we prove that for the so-called weakly bounded below Thomason filtrations the two t-structures have the same heart (therefore it is always locally finitely presented), and we show that they coincide if and only they are both compactly generated. Moreover, we achieve a complete characterisation of the local coherence for the hearts of the Thomason filtrations of finite length.

À la suite d’Agrippa, maint sceptique a argué de la pluralité des systèmes pour ruiner toute ambition de vérité philosophique : des systèmes contradictoires ne pouvant être vrais simultanément, leurs prétentions respectives s’annulent. L’argument n’a pourtant de valeur que si la pluralité des systèmes est elle-même irrationnelle. Or plusieurs philosophes ont rationalisé la diversité des systèmes philosophiques, suggérant par là que la raison puisse s’approprier sa propre limite ; notamment Kant, dans l’« Histoire de la raison pure » qui conclut la Critique de la raison pure (1781) ; Hegel, dans les Leçons sur l’histoire de la philosophie (1805–1830) ; Victor Cousin, dans Du Vrai, du beau et du bien (1828) et l’Histoire générale de la philosophie (1863) ; Charles Renouvier, dans l’Esquisse d’une classification systématique des doctrines philosophiques (1885–1886) ; et Jules Vuillemin, dans Nécessité ou contingence (1984).Étudier de manière interne chacune de ces entreprises permet de déterminer quels en sont les critères fondamentaux, la forme mathématique générale, et le but philosophique. L’histoire kantienne de la raison pure, injustement dédaignée, repose sur les concepts fondamentaux du criticisme, structure maint chapitre des trois Critiques, et annonce la paix philosophique perpétuelle dont est porteur le criticisme. Les Leçons de Hegel ne sont ni un résumé empirique ni une histoire biaisée de la philosophie : fondées sur la Logique et la Phénoménologie, elles mettent au jour la dialectique interne des systèmes. La classification de Renouvier n’est pas, comme on le dit parfois, a posteriori, mais repose au contraire sur le jeu a priori d’une table des catégories et d’une théorie de la contradiction. Enfin, la classification vuilleminienne des systèmes, qui s’appuie sur une classification des formes de prédication, généralise la classification kantienne. Seule la classification de Victor Cousin s’avère finalement a posteriori.Ancrées dans les concepts fondamentaux de chacune de ces doctrines, ces classifications montrent qu’un système peut construire l’image des autres et de leurs relations aussi rigoureusement qu’il décrit le monde : les relations entre systèmes ne sont pas moins structurales que les systèmes eux-mêmes. / Following the example of Agrippa, a lot a sceptics argued that, because of the plurality of philosophical systems, there could be no unique philosophical truth: contradictory systems could not be true at the same time. But this argument presupposes that this plurality is itself irrational. And yet some philosophers took the diversity of philosophical systems as rational, suggesting that reason was able to take possession of its own boundary: Kant, in the “History of pure reason” of the Critique of Pure Reason (1781); Hegel, in the Lessons on the History of Philosophy (1805–1830); Victor Cousin, in his books Du Vrai, du beau et du bien (1828) and the Histoire générale de la philosophie (1863); Charles Renouvier, in the Esquisse d’une classification systématique des doctrines philosophiques (1885–1886); and Jules Vuillemin, in Necessity or Contingency (1984).By examining the internal structure of each of these attempts, we can show their main criteria, their general mathematical form, and their philosophical aim. Kant’s “History of Pure Reason” uses the fundamental concepts of criticism, plays a structuring role in the Critique of Pure Reason, and forecasts the perpetual peace of criticism. Hegel’s Lessons are neither an empirical summary nor a biased history of philosophy: they are grounded on Hegel’s Logic and Phenomenology, and reveal the internal dialectic of systems. Renouvier’s classification is not a posteriori, but combines an a priori table of categories with a theory of contradiction. Finally, Vuillemin’s classification of systems, which is grounded on a classification of elementary sentences, is a generalization of Kant’s classification. Only Victor Cousin’s classification is a posteriori.These classifications find their roots in the fundamental concepts of each of these systems. A philosophical system is thus able to account not only for the world, but also for other systems and for their relationship. The relationship between systems is not less structural than systems themselves are.

À la suite d'Agrippa, maint sceptique a argué de la pluralité des systèmes pour ruiner toute ambition de vérité philosophique : des systèmes contradictoires ne pouvant être vrais simultanément, leurs prétentions respectives s'annulent. L'argument n'a pourtant de valeur que si la pluralité des systèmes est elle-même irrationnelle. Or plusieurs philosophes ont rationalisé la diversité des systèmes philosophiques, suggérant par là que la raison puisse s'approprier sa propre limite ; notamment Kant, dans l'" Histoire de la raison pure " qui conclut la Critique de la raison pure (1781) ; Hegel, dans les Leçons sur l'histoire de la philosophie (1805-1830) ; Victor Cousin, dans Du Vrai, du beau et du bien (1828) et l'Histoire générale de la philosophie (1863) ; Charles Renouvier, dans l'Esquisse d'une classification systématique des doctrines philosophiques (1885-1886) ; et Jules Vuillemin, dans Nécessité ou contingence (1984).Étudier de manière interne chacune de ces entreprises permet de déterminer quels en sont les critères fondamentaux, la forme mathématique générale, et le but philosophique. L'histoire kantienne de la raison pure, injustement dédaignée, repose sur les concepts fondamentaux du criticisme, structure maint chapitre des trois Critiques, et annonce la paix philosophique perpétuelle dont est porteur le criticisme. Les Leçons de Hegel ne sont ni un résumé empirique ni une histoire biaisée de la philosophie : fondées sur la Logique et la Phénoménologie, elles mettent au jour la dialectique interne des systèmes. La classification de Renouvier n'est pas, comme on le dit parfois, a posteriori, mais repose au contraire sur le jeu a priori d'une table des catégories et d'une théorie de la contradiction. Enfin, la classification vuilleminienne des systèmes, qui s'appuie sur une classification des formes de prédication, généralise la classification kantienne. Seule la classification de Victor Cousin s'avère finalement a posteriori.Ancrées dans les concepts fondamentaux de chacune de ces doctrines, ces classifications montrent qu'un système peut construire l'image des autres et de leurs relations aussi rigoureusement qu'il décrit le monde : les relations entre systèmes ne sont pas moins structurales que les systèmes eux-mêmes.

A presente tese carrega o ônus de afirmar a relevância dos textos de Henry David Thoreau para a filosofia moral. Duas estratégias paralelas foram utilizadas para cumprir a tarefa. A primeira consiste na discussão pormenorizada de um conjunto de autores que apresentaram para Thoreau diferentes visões sobre a moralidade e o papel da filosofia na tecitura de uma vida digna de ser vivida: o Unitarismo de William Ellery Channing, as doutrinas do Scottish Common Sense de Dugald Stewart e Thomas Reid, o utilitarismo teológico de William Paley, o intuicionismo racional dos Platonistas de Cambridge (representados aqui por Ralph Cudworth), Orestes Brownson e Ralph Waldo Emerson – dois dos principais nomes do Transcendentalismo da Nova Inglaterra e Samuel Taylor Coleridge, Victor Cousin e Thomas Carlyle – primeiros intérpretes do Idealismo Alemão para o mundo de língua inglesa. A segunda estratégia articula a reação de Thoreau a essas diferentes posições sobre a moralidade, mostrando como, a partir dessa reação, ele foi capaz de formular um exercício de pensamento moral, cristalizado, emblematicamente, na escritura de Walden. O conceito de “identidade ficcional” foi pensado para capturar as diferentes técnicas utilizadas nesse exercício. / The present thesis carries the burden of asserting the relevance of Henry David Thoreau´s texts for moral philosophy. Two parallel strategies have been used to complete the task. The first is a thorough discussion of a group of authors who presented to Thoreau different views on morality and the role of philosophy in the weaving of a life worthy of being lived: William Ellery Channing´s Unitarianism, the doctrines of the Scottish Common Sense - Dugald Stewart and Thomas Reid, William Paley´s theological utilitarianism, rational intuitionism of Cambridge Platonists (represented here by Ralph Cudworth), Orestes Brownson and Ralph Waldo Emerson - two of the leading names of New England Transcendentalism and Samuel Taylor Coleridge, Victor Cousin and Thomas Carlyle - first interpreters of German Idealism to the English-speaking world. The second strategy articulates Thoreau´s reaction to these different positions on morality, showing how, from this reaction, he was able to formulate an exercise in moral thinking, crystallized, emblematically, in the writing of Walden. The concept of "fictional identity" was designed to capture different techniques used in this exercise.

A presente tese carrega o ônus de afirmar a relevância dos textos de Henry David Thoreau para a filosofia moral. Duas estratégias paralelas foram utilizadas para cumprir a tarefa. A primeira consiste na discussão pormenorizada de um conjunto de autores que apresentaram para Thoreau diferentes visões sobre a moralidade e o papel da filosofia na tecitura de uma vida digna de ser vivida: o Unitarismo de William Ellery Channing, as doutrinas do Scottish Common Sense de Dugald Stewart e Thomas Reid, o utilitarismo teológico de William Paley, o intuicionismo racional dos Platonistas de Cambridge (representados aqui por Ralph Cudworth), Orestes Brownson e Ralph Waldo Emerson – dois dos principais nomes do Transcendentalismo da Nova Inglaterra e Samuel Taylor Coleridge, Victor Cousin e Thomas Carlyle – primeiros intérpretes do Idealismo Alemão para o mundo de língua inglesa. A segunda estratégia articula a reação de Thoreau a essas diferentes posições sobre a moralidade, mostrando como, a partir dessa reação, ele foi capaz de formular um exercício de pensamento moral, cristalizado, emblematicamente, na escritura de Walden. O conceito de “identidade ficcional” foi pensado para capturar as diferentes técnicas utilizadas nesse exercício. / The present thesis carries the burden of asserting the relevance of Henry David Thoreau´s texts for moral philosophy. Two parallel strategies have been used to complete the task. The first is a thorough discussion of a group of authors who presented to Thoreau different views on morality and the role of philosophy in the weaving of a life worthy of being lived: William Ellery Channing´s Unitarianism, the doctrines of the Scottish Common Sense - Dugald Stewart and Thomas Reid, William Paley´s theological utilitarianism, rational intuitionism of Cambridge Platonists (represented here by Ralph Cudworth), Orestes Brownson and Ralph Waldo Emerson - two of the leading names of New England Transcendentalism and Samuel Taylor Coleridge, Victor Cousin and Thomas Carlyle - first interpreters of German Idealism to the English-speaking world. The second strategy articulates Thoreau´s reaction to these different positions on morality, showing how, from this reaction, he was able to formulate an exercise in moral thinking, crystallized, emblematically, in the writing of Walden. The concept of "fictional identity" was designed to capture different techniques used in this exercise.

A presente tese carrega o ônus de afirmar a relevância dos textos de Henry David Thoreau para a filosofia moral. Duas estratégias paralelas foram utilizadas para cumprir a tarefa. A primeira consiste na discussão pormenorizada de um conjunto de autores que apresentaram para Thoreau diferentes visões sobre a moralidade e o papel da filosofia na tecitura de uma vida digna de ser vivida: o Unitarismo de William Ellery Channing, as doutrinas do Scottish Common Sense de Dugald Stewart e Thomas Reid, o utilitarismo teológico de William Paley, o intuicionismo racional dos Platonistas de Cambridge (representados aqui por Ralph Cudworth), Orestes Brownson e Ralph Waldo Emerson – dois dos principais nomes do Transcendentalismo da Nova Inglaterra e Samuel Taylor Coleridge, Victor Cousin e Thomas Carlyle – primeiros intérpretes do Idealismo Alemão para o mundo de língua inglesa. A segunda estratégia articula a reação de Thoreau a essas diferentes posições sobre a moralidade, mostrando como, a partir dessa reação, ele foi capaz de formular um exercício de pensamento moral, cristalizado, emblematicamente, na escritura de Walden. O conceito de “identidade ficcional” foi pensado para capturar as diferentes técnicas utilizadas nesse exercício. / The present thesis carries the burden of asserting the relevance of Henry David Thoreau´s texts for moral philosophy. Two parallel strategies have been used to complete the task. The first is a thorough discussion of a group of authors who presented to Thoreau different views on morality and the role of philosophy in the weaving of a life worthy of being lived: William Ellery Channing´s Unitarianism, the doctrines of the Scottish Common Sense - Dugald Stewart and Thomas Reid, William Paley´s theological utilitarianism, rational intuitionism of Cambridge Platonists (represented here by Ralph Cudworth), Orestes Brownson and Ralph Waldo Emerson - two of the leading names of New England Transcendentalism and Samuel Taylor Coleridge, Victor Cousin and Thomas Carlyle - first interpreters of German Idealism to the English-speaking world. The second strategy articulates Thoreau´s reaction to these different positions on morality, showing how, from this reaction, he was able to formulate an exercise in moral thinking, crystallized, emblematically, in the writing of Walden. The concept of "fictional identity" was designed to capture different techniques used in this exercise.