In this study, we use temporally aligned word embeddings and a large diachronic corpus of English to quantify language change in a data-driven, scalable way, which is grounded in language use. We show a unique and reliable relation between measures of language change and age of acquisition (AoA) while controlling for frequency, contextual diversity, concreteness, length, dominant part of speech, orthographic neighborhood density, and diachronic frequency variation. We analyze measures of language change tackling both the change in lexical representations and (...) the change in the relation between lexical representations and the words with the most similar usage patterns, showing that they capture different aspects of language change. Our results show a unique relation between language change and AoA, which is stronger when considering neighborhood-level measures of language change: Words with more coherent diachronic usage patterns tend to be acquired earlier. The results support theories positing a link between ontogenetic and ethnogenetic processes in language. (shrink)

We introduce a sequent calculus B for a new logic, named basic logic. The aim of basic logic is to find a structure in the space of logics. Classical, intuitionistic, quantum and non-modal linear logics, are all obtained as extensions in a uniform way and in a single framework. We isolate three properties, which characterize B positively: reflection, symmetry and visibility. A logical constant obeys to the principle of reflection if it is characterized semantically by an equation binding it with (...) a metalinguistic link between assertions, and if its syntactic inference rules are obtained by solving that equation. All connectives of basic logic satisfy reflection. To the control of weakening and contraction of linear logic, basic logic adds a strict control of contexts, by requiring that all active formulae in all rules are isolated, that is visible. From visibility, cut-elimination follows. The full, geometric symmetry of basic logic induces known symmetries of its extensions, and adds a symmetry among them, producing the structure of a cube. (shrink)

The first issue of Artificial Intelligence and Law journal was published in 1992. This paper provides commentaries on nine significant papers drawn from the Journal’s second decade. Four of the papers relate to reasoning with legal cases, introducing contextual considerations, predicting outcomes on the basis of natural language descriptions of the cases, comparing different ways of representing cases, and formalising precedential reasoning. One introduces a method of analysing arguments that was to become very widely used in AI and Law, namely (...) argumentation schemes. Two relate to ontologies for the representation of legal concepts and two take advantage of the increasing availability of legal corpora in this decade, to automate document summarisation and for the mining of arguments. (shrink)

Within the technical frame supplied by the algebraic variety of diagonalizable algebras, defined by R. Magari in [2], we prove the following: Let T be any first-order theory with a predicate Pr satisfying the canonical derivability conditions, including Löb's property. Then any formula in T built up from the propositional variables $q,p_{1},...,p_{n}$ , using logical connectives and the predicate Pr, has the same "fixed-points" relative to q (that is, formulas $\psi (p_{1},...,p_{n})$ for which for all $p_{1},...,p_{n}\vdash _{T}\phi (\psi (p_{1},...,p_{n}),p_{1},...,p_{n})\leftrightarrow \psi (...) (p_{1},...,p_{n})$ ) of a formula $\phi ^{\ast}$ of the same kind, obtained from φ in an effective way. Moreover, such $\phi ^{\ast}$ is provably equivalent to the formula obtained from φ substituting with $\phi ^{\ast}$ itself all the occurrences of q which are under Pr. In the particular case where q is always under Pr in φ, $\phi ^{\ast}$ is the unique (up to provable equivalence) "fixed-point" of φ. Since this result is proved only assuming Pr to be canonical, it can be deduced that Löb's property is, in a sense, equivalent to Gödel's diagonalization lemma. All the results are proved more generally in the intuitionistic case. (shrink)

Thomas Reid (1710–1796) presented a two-dimensional geometry of the visual field in his Inquiry into the human mind (1764), whose axioms are different from those of Euclidean plane geometry. Reid’s ‘geometry of visibles’ is the same as the geometry of the surface of the sphere, described without reference to points and lines outside the surface itself. Interpreters of Reid seem to be divided in evaluating the significance of his geometry of visibles in the history of the discovery of non-Euclidean geometries. (...) The question will be reexamined with particular attention given to his unpublished manuscripts. These include comments on Saccheri’s work and Reid’s repeated attempts to derive Euclid’s parallel postulate from the axioms of incidence. (shrink)

We introduce a sequent calculusBfor a new logic, named basic logic. The aim of basic logic is to find a structure in the space of logics. Classical, intuitionistic. quantum and non-modal linear logics, are all obtained as extensions in a uniform way and in a single framework. We isolate three properties, which characterizeBpositively: reflection, symmetry and visibility.A logical constant obeys to the principle of reflection if it is characterized semantically by an equation binding it with a metalinguistic link between assertions, (...) and if its syntactic inference rules are obtained by solving that equation. All connectives of basic logic satisfy reflection.To the control of weakening and contraction of linear logic, basic logic adds a strict control of contexts, by requiring that all active formulae in all rules are isolated, that is visible. From visibility, cut-elimination follows. The full, geometric symmetry of basic logic induces known symmetries of its extensions, and adds a symmetry among them, producing the structure of a cube. (shrink)

Richard Owen has been condemned by Darwinians as an anti-evolutionist and an essentialist. In recent years he has been the object of a revisionist analysis intended to uncover evolutionary elements in his scientific enterprise. In this paper I will examine Owen's evolutionary hypothesis and its connections with von Baer's idea of divergent development. To give appropriate importance to Owen's evolutionism is the first condition to develop an up-to-date understanding of his scientific enterprise, that is to disentagle Owen's contribution to the (...) modernization of typology and morphology. I will argue that Owen's Platonic essentialism is rhetorical and incongruous. On the contrary, an interpretation of the archetype based on Aristotle's biological works makes possible a new conception of type, based on a homeostatic mechanism of stability. The renewal of morphology hinges on homological correspondences and a homeostatic process is also the origin of serial and special homology. I will argue that special homology shows an evolutionary orientation insofar as it is a typically inter-specific character while serial homology is determined through an elementary usage of the categories of developmental morphology. (shrink)

This paper proposes to model legal reasoning asdialectical theory-constructiondirected by teleology. Precedents are viewed asevidence to be explained throughtheories. So, given a background of factors andvalues, the parties in a case canbuild their theories by using a set of operators,which are called theory constructors.The objective of each party is to provide theoriesthat both explain the evidence (theprecedents) and support the decision wished by thatparty. This leads to theory-basedargumentation, i.e., a dialectical exchange ofcompeting theories, which support opposedoutcomes by explaining the same (...) evidence and appealingto the same values. The winneris the party that can reply with a more coherent theoryto all theories of its adversary. (shrink)

Thomas Reid presented a two-dimensional geometry of the visual field in his Inquiry into the Human Mind (1764). The axioms of this geometry are different from those of Euclidean plane geometry. The ‘geometry of visibles’ is the same as the geometry of the surface of the sphere, described without reference to points and lines outside the surface itself. In a recent article, James Van Cleve has argued that Reid can secure a non-Euclidean geometry of visibles only at the cost of (...) abandoning his direct realist theory of perception, and reintroducing sense-data. The question will be reexamined by considering two aspects of Reid’s theory of vision: the claim that we do not directly perceive distance by sight and Reid’s characterization of visible figure as a partial notion of an external object. (shrink)

Pretopologies were introduced in [S], and there shown to give a complete semantics for a propositional sequent calculus BL, here called basic linear logic, as well as for its extensions by structural rules,ex falso quodlibetor double negation. Immediately after Logic Colloquium '88, a conversation with Per Martin-Löf helped me to see how the pretopology semantics should be extended to predicate logic; the result now is a simple and fully constructive completeness proof for first order BL and virtually all its extensions, (...) including the usual, or structured, intuitionistic and classical logic. Such a proof clearly illustrates the fact that stronger set-theoretic principles and classical metalogic are necessary only when completeness is sought with respect to a special class of models, such as the usual two-valued models.To make the paper self-contained, I briefly review in §1 the definition of pretopologies; §2 deals with syntax and §3 with semantics. The completeness proof in §4, though similar in structure, is sensibly simpler than that in [S], and this is why it is given in detail. In §5 it is shown how little is needed to obtain completeness for extensions of BL in the same language. Finally, in §6 connections with proofs with respect to more traditional semantics are briefly investigated, and some open problems are put forward. (shrink)

According to Reid, color sensations are not extended nor are they arranged in figured patterns. Reid further claimed that ‘there is no sensation appropriated to visible figure.’ Reid justified these controversial claims by appeal to Cheselden's report of the experiences of a young man affected by severe cataracts, and by appeal to cases of perception of visible figure without color. While holding fast to the principle that sensations are not extended, Dugald Stewart tried to show that ‘a variety of colour (...) sensations is a necessary means for the perception of visible figure.’ According to John Fearn, two motives appear to be central to Reid's views about color sensations and extension: his commitment to the Cartesian doctrine of the immateriality of the soul, and his attempt to evade ‘Hume's dilemma’ about the existence and immateriality of the soul. (shrink)

In order to illustrate the difference between sensation and perception, Reid imagines a blind man that by ‘some strange distemper’ has lost all his notions of external objects, but has retained the power of sensation and reasoning. Reid argues that since sensations do not resemble external objects, the blind man could not possibly infer from them any notion of primary qualities. Condillac proposed a similar thought experiment in the Treatise on Sensations. I argue that Condillac can reach a conclusion opposite (...) to that of Reid only by assuming that some particular collections of sensations do indeed resemble the qualities of external objects. Reid had considered a similar case in a manuscript, but he again notices that such complex collections sensations do not resemble the qualities of external objects. (shrink)

In der Reihe werden herausragende monographische Untersuchungen und Sammelbände zu allen Aspekten der Philosophie Kants veröffentlicht, ebenso zum systematischen Verhältnis seiner Philosophie zu anderen philosophischen Ansätzen in Geschichte und Gegenwart. Veröffentlicht werden Studien, die einen innovativen Charakter haben und ausdrückliche Desiderate der Forschung erfüllen. Die Publikationen repräsentieren den aktuellsten Stand der Forschung.

According to Reid, opinions that contradict the principles of common sense are not only false but also absurd. Nature has given us an emotion that reveals the absurdity of an opinion: the emotion of ridicule. An appeal to ridicule in philosophical arguments may easily be discounted as a logical fallacy in the same manner as an appeal to the common consent of people. This essay traces the origins of Reid's defense of ridicule in the works of Addison, Hutcheson, Shaftesbury and (...) Campbell. Reid rejected a non-epistemic view of the sense of ridicule. According to Reid, ridicule includes both a feeling and a particular act of judgment based on the principles of common sense. (shrink)

I shall compare two views of legal concepts: as nodes in inferential nets and as categories in an ontology (a conceptual architecture). Firstly, I shall introduce the inferential approach, consider its implications, and distinguish the mere possession of an inferentially defined concept from the belief in the concept’s applicability, which also involves the acceptance of the concept’s constitutive inferences. For making this distinction, the inferential and eliminative analysis of legal concepts proposed by Alf Ross will be connected to the views (...) on theoretical concepts in science advanced by Frank Ramsey and Rudolf Carnap. Consequently, the mere comprehension of a legal concept will be distinguished from the application of the concept to a particular legal system, since application presupposes a doctrinal commitment, namely, the belief that the inferences constituting the concept hold in that system. Then, I shall consider how concepts can be characterised by defining the corresponding terms and placing them within an ontology. Finally, I shall argue that there is a tension between the inferential and the ontological approach, but that both need to be taken into account, to capture the meaning and the cognitive function of legal concepts. (shrink)

Martin-Löf Type Theory is both an important and practical formalization and a focus for a charismatic view of the foundations of mathematics. Per Martin-Löf's work has been of huge significance in the fields of logic and the foundations of mathematics, and has important applications in areas such as computing science and linguistics. This volume celebrates the twenty-fifth anniversary of the birth of the subject, and is an invaluable record both of areas of currentactivity and of the early development of the (...) subject. Also published for the first time is one of Per Martin-Löf's earliest papers. (shrink)

While Hume had a favorable opinion of the new commercial society, Reid envisioned a utopian system that would eliminate private property and substitute the profit incentive with a system of state-conferred honors. Reid’s predilection for a centralized command economy cannot be explained by his alleged discovery of market failures, and has to be considered in the context of his moral psychology. Hume tried to explain how the desire for gain that motivates the merchant leads to industry and frugality. These, in (...) their turn, benefit all society. Reid still saw the desire for money as a degenerate form of the desire for power. The contrast between Hume and Reid, however, has not to be taken too far. On some particular matters of economic policy, such as paper credit, Hume and Reid eventually came to similar views. (shrink)

This article proposes a formal analysis of a fundamental aspect of legal reasoning: dealing with normative conflicts. Firstly, examples are illustrated concerning the dynamics of legal systems, the application of rules and exceptions, and the semantic indeterminacy of legal sources. Then two approaches to cope with conflicting information are presented: the preferred theories of Brewka, and the belief change functions of Alchourrón, Gärdenfors, and Makinson. The relations between those approaches are closely examined, and some aspects of a model of reasoning (...) with normative conflicts are outlined. Since this model takes into account an ordering of the involved regulations, criteria to order legal norms are finally specified. (shrink)

In a recent article on Reid’s theory of single and double vision, James Van Cleve considers an argument against direct realism presented by Hume. Hume argues for the mind-dependent nature of the objects of our perception from the phenomenon of double vision. Reid does not address this particular argument, but Van Cleve considers possible answers Reid might have given to Hume. He finds fault with all these answers. Against Van Cleve, I argue that both appearances in double vision could be (...) considered visible figures of the object, and show how this solution might preserve Reid’s direct realism. However, this solution is not compatible with the single appearance of an object predicted by Reid’s theory of single and double vision. This consequence will appear evident once we consider the critique of Reid’s theory of single and double vision formulated by William Charles Wells (1757-1817). Wells argues that Reid’s theory is either incomplete or incompatible with other claims made by Reid. It is incomplete since it fails to specify the unique direction in which we the object in single vision; if it not incomplete and is compatible with the law of monocular direction given by Reid, then it is incompatible with Reid’s claim that we do not perceive immediately distance by sight. (shrink)

Gli antichi Greci la chiamavano métis. Parola comune e anche nome mitologico di divinità. Se consultiamo il vocabolario, ne troviamo due significati: "saggezza" ispirata a "prudenza" e "disegno", nel senso di "piano" concepito da qualcuno. La flessibilità ha a che fare soprattutto con il secondo significato, perché è razionalità strategica e agonistica, in cui la duttilità è insieme ragion d'essere, modo di operare e scopo. Giovanni Bottiroli sostiene da tempo la necessità di elaborare una filosofia di tipo modale, che (...) apra le categorie della logica classica alla coppia rigido/flessibile. In questo saggio porta a compimento una teoria estremamente articolata degli stili di pensiero, la sola che giudica in grado di comprendere l'eterogeneità della mente, il pluralismo logico e semantico, l'identità come polisemia. Se definiamo "rigido" ogni soggetto il cui modo d'essere è la coincidenza con se stesso, la flessibilità non può ridursi infatti a una rigidità indebolita: è inclusiva e avvolgente e le spetta il primato sul piano logico, etico ed estetico. Perché è la flessibilità a renderci liberi. (shrink)

. I will argue that the concept of law is a normative notion, irreducible to any factual description. Its conceptual function is that of relating certain properties a norm may possess to the conclusion that the norm is legally binding, namely, that it deserves to be endorsed and applied in legal reasoning. Legal validity has to be distinguished from other, more demanding, normative ideas, such as moral bindingness or legal optimality.

O presente ensaio, aqui publicado em tradução original para Português, constitui uma secção muito significativa da conhecida obra de Giovanni B. Sala sobre Lonergan e a sua relação com Kant. Trata-se de um estudo comparativo das teorias do conhecimento de Immanuel Kant e de Bernard Lonergan, tomando-se como ponto de partida uma análise do estatuto do a priori no conhecimento humano tal como no-lo apresenta a Crítica da Razão Pura, de Kant, para depois se apresentarem as respectivas lacunas, insuficiências (...) e contradições mediante o recurso a Insight, a obra mestra de Bernard Lonergan. Para o filósofo jesuíta, com efeito, o interesse primordial consiste em realçar a possibilidade do conhecimento do ser, possibilidade essa fundamentada na natureza do juízo e na natureza do questionamento humano. Para além disso, mostra-se também como em ordem a ultrapassar a impossibilidade do conhecimento numénico, a reflexão lonerganiana sublinha o conhecimento como estrutura empírica, inteligente, racional e responsável, capaz de captar a realidade, uma vez que esta é, segundo Lonergan, intrinsecamente inteligível. /// The present text is a translation into Portuguese of a section of a work by Giovanni Sala on Lonergan and his relation with Kant. It amounts to a comparative study of the gnoseologies of Kand and Lonergan, whereby the starting point is an analysis of the statute of the a priori in human knowledge such as we find it in the Critique of Pure Reason of Kant, so that in the process the author also shows the corresponding insufficiencies and contradictions by means of a reading of the work Insight by Bernard Lonergan. For the Jesuit philosopher, the main interest of his gnoseology consists in an affirmation of the possibility of knowing being, possibility that is grounded in the nature of judgment itself and in the nature of human interro- gation. Moreover, the article also shows how in order to overcome the impossibility of noumenal knowledge, the lonerganian reflexion underlines knowledge as an empirical structure, intelligent, rational and responsible, able to capture reality. In the end, this is possible due to the fact that, for Lonergan, the real is intrinsically intelligible. (shrink)

In the present work Berkeley's theory of vision is considered in its historical origins, in its relation to Berkeley's general philosophical conceptions, and in its early reception. Berkeley's theory replaces an account of vision according to which distance and other spatial properties are deduced from elementary data through an unconscious geometric inference. This account of vision in terms of "natural geometry" was first introduced by Descartes and Malebranche. Among Berkeley's immediate sources of knowledge of the geometric theory of perception, a (...) key role was played by the treatise of dioptrics of William Molyneux, Dioptrica Nova. Berkeley's understanding of "natural geometry" relies closely on Molyneux's description of the mechanism of vision which avoids the complexities of the accounts of Descartes and Malebranche. In the first chapter Berkeley's theory is presented by way of contrast with Molyneux's theory. In the second chapter I consider the relation between the theory of vision and immaterialism. In the final chapter I examine one of the first criticisms of Berkeley's theory, that which is found in William Porterfield's Treatise on the Eye. Dept. of Philosophy. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1997.G72. Source: Masterss International, Volume: 37-01, page: 0076. Adviser: John P. Wright. Thesis --University of Windsor, 1997. (shrink)

According to Daniel Flage, Berkeley thinks that all necessary truths are founded on acts of will that assign meanings to words. After briefly commenting on the air of paradox contained in the title of Flage’s paper, and on the historical accuracy of Berkeley’s understanding of the abstractionist tradition, I make some remarks on two points made by Flage. Firstly, I discuss Flage’s distinction between the ontological ground of a necessary truth and our knowledge of a necessary truth. Secondly, I discuss (...) Flage’s attempt to show that, according to Berkeley, the resemblance relation does not constitute a necessary connection. (shrink)

Two theses appear to be central to Reid’s view of the visual field. By sight, we do not originally perceive depth or linear distance from the eye. By sight, we originally perceive the position that points on the surface of objects have with regard to the centre of the eye. In different terms, by sight, we originally perceive the compass direction and degree of elevation of points on the surface of objects with reference to the centre of the eye. I (...) consider various problems about distance perception and perception of position with regard to the centre of the eye raised by Reid’s texts. These questions are relevant to Reid’s description of the geometry of visibles as the “intrinsic” geometry of the surface of the sphere. (shrink)

Il saggio recensisce i primi quattro volumi dell’Annuario di studi filosofici “Anthropologica” – La differenza umana. Riduzionismo e antiumanesimo ; La struttura dei legami ; La vita in questione. Potenziamento o compimento dell'essere umano? ;Chi dice io? Riflessioni sull’identità personale – illustrando il programma di ricerca sviluppato dal gruppo interdisciplinare di studio promosso dal Centro Studi Jacques Maritain. Attraverso il ricorso all’impianto filosofico dell’antichità classica e cristiana, unitamente agli sviluppi contemporanei della tradizione personalista, gli autori affrontano numerose questioni dell’attuale dibattito (...) sull’umano: particolarmente significativo è il confronto con le diverse forme di antiumanesimo che in modo diretto o indiretto emergono nei settori delle scienze della vita, specialmente lì dove si profilano nuove possibilità di intervento sulla natura umana aperto dallo sviluppo tecnologico. (shrink)

The paper defends the theoretical strength and consistency of Rawls's constructivism, showing its ability to articulate and convincingly weave together several key ethical ideas; yet it questions the political relevance of this admirable normative architecture. After having illustrated Rawls's conception of moral agency and practical reason, the paper tackles two criticisms raised by Scheffler. First the allegation of naturalism based on Rawls's disdain of common sense ideas on desert is rebutted. It is then shown that, contrary to Scheffler's contention, Rawls (...) takes proper account of our moral sentiments in the process of constructing his normative theory. Finally, the second criticism is assessed, namely the inability of Rawls's theory to increase consent around liberal policies. Despite disagreement with details of Scheffler's argument, it is suggested that the failure of recent normative liberal theories to have a political impact belies their inability to take into proper consideration the reality of politics. A more realistic appraisal of political life and of historical events and developments are called for if political philosophy wants to be something more than an academic exercise. (shrink)

Reid’s rejection of the “theory of ideas” implies that sensations are not copies of external qualities such as extension and figure. Reid also says that not even the order of sensations is spatial. However, in his early manuscripts Reid did not deny that sensations are arranged spatially. He simply denied that our ideas of extension and figure are copied from any single atomic sensation. Only subsequently did Reid explicitly reject the view that sensations are arranged spatially. The question of the (...) spatiality of color sensation was a central concern of early interpreters of Reid, like Dugald Stewart, John Fearn, and William Hamilton. In particular, John Fearn thought that the denial of the spatiality of color sensations is the result of Reid’s commitment to the immateriality of the soul. Against Reid’s view, Fearn argued that the perception of visible figure necessarily implies the spatiality of color sensations. (shrink)

According to Thomas Reid, the development of natural sciences following the model of Newton's Principia and Optics would provide further evidence for the belief in a provident God. This project was still supported by his student, Dugald Stewart, in the early nineteenth century. John Fearn , an early critic of the Scottish common sense school, thought that the rise of ‘infidelity’ in the wake of scientific progress had shown that the apologetic project of Reid and Stewart had failed. In reaction (...) to Reid and Stewart, he proposed an idealist philosophy that would dispense with the existence of matter, and would thus cut at the root what he thought was the main source of modern atheism. In this paper, I consider Fearn's critique of Reid and Stewart in his main works: First Lines of the Human Mind and Manual of the Physiology of Mind . I also consider Fearn's arguments against Hume and in favour of a renewed apologetics in An Essay on the Philosophy of Faith and the Economy of Revelatio.. (shrink)

Thomas Reid is the foremost exponent of the Scottish 'common sense' school of philosophy. Educated at Marischal College in Aberdeen, Reid subsequently taught at King’s College, and was a founder of the Aberdeen Philosophical Society. His Inquiry Into the Human Mind on the Principles of Common Sense was published in 1764, the same year he succeeded Adam Smith as Professor of Moral Philosophy at the University of Glasgow. He resigned from active teaching duties in 1785 to devote himself to writing, (...) and published two more books — Essays on the Intellectual Powers of Man and Essays on the Active Powers of Man. Within a short time of publication, Reid’s works were translated into French and German, and greatly influenced debates in philosophy and psychology in Europe. His influence in the emerging colleges and universities of post-revolutionary America was even greater. Reid was widely regarded as David Hume’s most sophisticated contemporary critic. His critique of the "theory of ideas", that lay behind both Hume’s scepticism and Berkeley’s immaterialism, his critique of Locke’s theory of personal identity, and his defence of “moral liberty” against determinism, are all of enduring interest and significance. The aim of this comprehensive selection of his writings is to make the key elements of Reid’s philosophical work available to a new generation of readers. Two other philosophers of the ‘common sense’ school are featured in the Library of Scottish Philosophy— James Beattie and Dugald Stewart. (shrink)

The search for a synthesis between formalism and constructivism, and meditation on Gödel incompleteness, leads in a natural way to conceive mathematics as dynamic and plural, that is the result of a human achievement, rather than static and unique, that is given truth. This foundational attitude, called dynamic constructivism, has been adopted in the actual development of topology and revealed some deep structures that had remained hidden under other views. After motivations for and a brief introduction to dynamic constructivism, an (...) overview is given of the changes it induces in the practice of mathematics and in its foundation, and of the new results it allows to obtain. (shrink)

The theoretical system Lyell presented in 1830 was composed of three requirements or principles: 1) the Uniformity Principle which states that past geological events must be explained by the same causes now in operation; 2) the Uniformity of Rate Principle which states that geological laws operate with the same force as at present; 3) the Steady-state Principle which states that the earth does not undergo any directional change. The three principles form a single thesis called uniformitarianism which has been repeatedly (...) questioned and which has been reputed to be unable to face the competing directional synthesis based on the theory of the earth's cooling down. As a result, the significance of Lyell's system has been reduced to a simple actualism which admits the validity of the only Uniformity Principle. I believe that the only way to understand Lyell's role in the history of science is to maintain the unity of his synthesis. To show the Newtonian roots of this synthesis I will compare Lyell's principles and Newton's Rules of Reasoning. I will conclude with an analysis of the methodological function of principles in Lyell's scientific endeavour. (shrink)