Christiaan Huygens

I explain and assess here Huygens’ concept of relative motion. I show that it allows him to ground most of the Law of Inertia, and also to explain rotation. Thereby his concept obviates the need for Newton’s absolute space. Thus his account is a powerful foundation for mechanics, though not without some tension.

Este artigo apresenta uma análise crítica da possível disputa entre as teorias sobre luz e cores elaboradas por Newton e Huygens que teria ocorrido entre os séculos XVII e XIX. Com base em diversos estudos historiográficos já realizados sobre o tema, será mostrado que na Historiografia da Ciência a ideia de uma disputa entre as ópticas de Newton e Huygens é considerada ultrapassada. O artigo fornece um apanhado histórico da Óptica no período, oferecendo subsídios para que essa questão seja também problematizada no Ensino, assim como foi na Historiografia da Ciência atual.

SUMMARY. — Between 1652 and 1669 Christiaan Huygens discoverd the laws that govern the motions that perfectly hard bodies make when they collide with each other. His manuscripts reveal, far better than his published texts do, that he pursued an intellectual programm entirely devoted to finding a descriptive kinematics. Meanwhile Huygens' contemporaries, such as Leibniz, tried to interpret Huygens' own concepts from a dynamical point of view. By determining, step by step, the way that Huygens truly discovered the laws of motion of bodies after collision, we are led to a broad overview of Huygens' thought. The internal structures of both manuscripts and published essays on collisions shed light on some of Huygens' subsequent stands on various issues, which display their conceptual background and logical bases.
Résumé
RÉSUMÉ. — De 1652 à 1669 Christiaan Huygens établit l'ensemble des règles idéales par lesquelles le mouvement se communique par le choc des corps. Les manuscrits révèlent, mieux que ne le font les textes publiés, un parcours intellectuel résolument tourné vers une cinématique descriptive, lorsque ses contemporains, tel Leibniz, trouveront dans les travaux mêmes de Huygens la matière d'une authentique dynamique. En retrouvant pas à pas la façon dont les règles du choc ont été réellement construites par Huygens, c'est à une élucidation générale de la pensée huguenienne que l'on se trouve confronté. L'architecture interne des manuscrits puis celle des traités publiés sur le choc donnent une explication très nette des prises de position ultérieures de Huygens en leur restituant le fonds conceptuel qui leur assure cohérence et force.

The Amsterdam-based merchant and mathematics enthusiast Adriaen Verwer (1654/5-1717) was one of the few in the Dutch Republic to respond to the first edition of Newton’s Principia (1687). Based on a close study of his published work, his correspondence with the Scottish mathematician and astronomer David Gregory (1659-1708), and his annotations in his own copy of the first edition of the Principia, I shall scrutinise the impact of Newton’s ideas on Verwer’s thinking. The proposed analysis, that will add nuance to earlier findings, also has broader implications for our understanding of the introduction of Newton’s ideas in the Dutch Republic, as will be shown.

This essay focuses on a digital text analysis with AntConc computational linguistics tool in order to find, list and compare the most important key word occurrences and their collocations in some of Christiaan Huygens last writings, from 1686 to 1695 and posthumous. The greatest attention is payed to three key words – Animus, Potentia and Lex – related to the themes of God's power, divine and human intelligence, probabilistic epistemology, natural theology and plurality of worlds. In addition, these key words are used to select the letters written by Huygens to the most important of his contemporaries on the same topics. This challenge firstly involves demonstrating that his last writings on philosophical and theological reflections on mechanistic philosophy are not an anomaly within Huygens' wider work, and secondly showing that these are indications of Huygens' involvement in a number of theoretical debates in the second half of the seventeenth century.

This book is about scientific understanding. It is widely acknowledged that a central aim of science is to achieve understanding of the world around us, and that possessing such understanding is highly important in our present-day society. But what does it mean to achieve this understanding? What precisely is scientific understanding? These are philosophical questions that have not yet received satisfactory answers. While there has been an ongoing debate about the nature of scientific explanation since Carl Hempel advanced his covering law model in 1948, the related notion of understanding has been largely neglected because most philosophers regarded understanding as merely a subjective byproduct of objective explanations. By contrast, this book puts scientific understanding center stage. It is primarily a philosophical study, but also contains detailed historical case studies of scientific practice. In contrast to most existing studies in this area, it takes into account scientists’ views and analyzes their role in scientific debate and development. The aim of the book is to develop and defend a philosophical theory of scientific understanding that can describe and explain the historical variation of criteria for understanding actually employed by scientists. The theory does justice to the insights of such famous physicists as Werner Heisenberg and Richard Feynman, while bringing much-needed conceptual rigor to their intuitions. The scope of the proposed account of understanding is the natural sciences: while the detailed case studies derive from physics, examples from other sciences are presented to illustrate its wider validity.

TABLE OF CONTENTS
1. Introduction: The desire to understand
2. Understanding and the aims of science
3. Explanatory understanding: A plurality of models
4. A contextual theory of scientific understanding
5. Intelligibility and metaphysics: Understanding gravitation
6. Models and mechanisms: Physical understanding in the nineteenth
7. Visualizability and intelligibility: Insight into the quantum world
8. Conclusion: The many faces of understanding

Le Lettere di Pieter van Gent a Ehrenfried Walther von Tschirnhaus, qui riedite e tradotte, costituiscono un documento prezioso per ricostruire l’ambiente culturale olandese degli anni 1675-1690. In questo libro divengono il punto di partenza per riesaminare la genesi dell’editio posthuma spinoziana e la sua complicata storia redazionale.
Di questa storia sono parte essenziale i profili intellettuali di Lodewijk Meijer, Jarig Jelles, Pieter van Gent, Georg Hermann Schuller, come anche l’attività editoriale di Jan Rieuwertsz e il complesso rapporto intellettuale di Tschirnhaus con Leibniz e Christiaan Huygens.

In this work, I focus on one of Galileo's concepts which was neither mathematically nor empirically derived, but instead based on a fundamental intuition regarding the nature of motion: that all mechanical phenomena can be treated in the same way, using the same mathematical and conceptual apparatus. This was Galileo's concept of 'correspondence', and I follow it from its origins at the turn of the 17th century through Thomas Harriot, Marin Mersenne and ultimately to Christiaan Huygens.
At the centre of the concept of correspondence was that phenomena which looked similar really were the same; they were separate instances of the same fundamental processes. Hanging chains and projectile trajectories did not form the same curve by coincidence; they formed the same curve because both were produced by the same competition between vertical and horizontal tendencies. Correspondences were one of the major motivating and legitimising factors behind both Galileo and Huygens' desire to treat all of nature mathematically. This conceptual structure justified their treatment of all of mechanics as mathematically the same.
Harriot and Mersenne's roles in this story are to show how contemporaries of Galileo could approach the same topic in drastically different ways. Unlike Huygens, neither Harriot nor Mersenne understood the concept of correspondences. While Galileo and Huygens relied crucially on correspondences to understand natural phenomena, both Harriot and Mersenne were able to achieve many important results in mechanics without it. This work is the biography of a concept; one that is contingent, constructed, frequently fruitful but not a historical or scientific necessity.