Christiaan Huygens’s late writings, ranging from 1686 to 1695, bear witness to his philosophical and theological reflections. In his Cosmotheoros, which was intended for publication, and other late writings that can be regarded as its preparatory drafts, Huygens deals with issues central to seventeenth-century philosophical debates: God’s power, divine and human intelligence, probabilistic epistemology, natural theology, and the plurality of worlds. This paper explains how Huygens’s reflections on animals and their souls, rational or not, play a key role in (...) his epistemological reflections on natural theology. The issue of animal generation, as well as of animal souls, is crucial to identifying elements of continuity between the scientific topics of Huygens’s works, and may be considered as the point of intersection between his understanding of mechanism and of the teleology of nature. This neglected perspective on Huygens’s philosophical-natural animism reveals key elements of his model of rationality and of his attitude towards religion, demonstrating his involvement in the debate over animism, in which he seems to have been strongly influenced by English Protestant empiricism. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Journal of the History of Ideas 61.3 (2000) 415-432 [Access article in PDF] Christiaan Huygens's Attitude toward Animals Nathaniel Wolloch The debate on the status of animals has interested people since ancient times. In the early modern era this debate reached one of its most historically important and sedulous stages, drawing the attention of some of the most famous minds in Europe. Curiously enough, the historiography of this (...) debate has failed to take cognizance of the part played in it by the famous Dutch scientist Christiaan Huygens (1629-95), renowned for his invention of the pendulum clock, founding of the wave theory of light, and discovery of the true shape of the rings of Saturn, to name only a few of his prolific and varied activities. 1 While Huygens's contribution does not occupy a historically central part in this debate, which did not usually directly engross his attention, it is possible, based on some of his writings and activities, to piece together a picture of his general attitude toward animals. Such a study, as presented here, reveals more than anecdotal importance, since it both entails and affords an enlightening discussion of the connection between philosophy, science, and the treatment of animals, a discussion, moreover, which is relevant to the understanding not only of the early modern debate on animals, but also to the current debate of this issue. [End Page 415]One of the most prevalent features of the development of the attitude toward animals has been the recurrence of anthropocentric arguments. Such arguments were exhibited both by theriophiles (lovers of animals) and anti-theriophiles. 2 A significant instance of this is the recurring argument that harming animals is not bad in itself but rather because it might lead to the harming or corruption of human beings. While such an approach in effect states that those who are kind to animals would also be kind to human beings, it also implies that cruelty toward animals is excusable if committed to advance good causes, such as science and medicine. 3 Such anthropocentric views ultimately derive from both classical culture and philosophy, and especially the notion, rooted in biblical cosmology, according to which all of nature was given to man for his use by God, i.e., man was given the stewardship of nature. 4Theriophilic views which tend to regard animals as sentient beings in their own right became relatively common in early modern times. The most influential of these theriophiles was Michel de Montaigne, known for his love and praise [End Page 416] of animals, 5 and among the many theriophiles influenced by his views one of the most important was his disciple Pierre Charron. 6However, the most influential early modern view of animals, which became the main reference-point for the debate on animals, was anti-theriophilic. This was the Cartesian theory of the "beast-machine," which viewed animals as mere automata, devoid of an immortal soul as possessed by human beings; they were regarded as devoid of mind, and their behavior was compared to that of a clock. Descartes himself seems to have been rather agnostic regarding this issue. He did not deny animals some capacity for feeling but claimed that it was more probable they were senseless automata than beings with souls like human beings. 7 However, while many theriophiles attacked the beast-machine theory, its anti-theriophilic implications were developed and radicalized by various seventeenth-century Cartesians beyond what Descartes himself probably intended. The most prominent example of this was the leading Cartesian Nicolas Malebranche. The French intellectual Bernard Le Bovier, sieur de Fontenelle, related how he saw Malebranche, a generally kind man, kick a pregnant bitch, and when confronted with his (Fontenelle's) alarm, regarded this act as inconsequential, claiming that she did not feel a thing. 8 As cruel as the beast-machine [End Page 417] theory may seem, however, one should remember that it tried to explain away the suffering of animals. It implied that had such suffering been proven to exist, it would have required moral consideration. The views of Spinoza... (shrink)

Entre les premiers developpements de la mecanique galileenne et la publication des Principia de Newton, s'est jouee une transformation radicale de la philosophie naturelle des modernes. Mathematiques, sciences de la nature et techniques de precision ont faconne d'une part une nouvelle maniere, active et operatoire, d'interroger la nature, et d'autre part une image du monde fondee sur l'idee d'une rationalite integrale des phenomenes. Interlocuteur infatigable de Mersenne, Galilee, Descartes, Leibniz ou Newton, Christiaan Huygens (1629-1695) a assure un lien necessaire (...) pour son epoque entre l'assimilation critique des Principes de la philosophie de Descartes, dont il retient l'exigence d'intelligibilite dans la conduite de la science, et la reception - critique elle aussi - des Principes mathematiques newtoniens. La methode de Huygens se structure dans les apports cartesien et galileen: choc des corps, oscillations du pendule, etude de la force et du mouvement en tant qu'expression de rapports geometriques, caracterisation de la nature de la lumiere sont autant de champs dans lesquels il est impossible de ne pas voir l'impregnation d'un questionnement philosophique permanent. C'est donc en philosophe tout autant qu'en physicien qu'il s'oppose aux definitions newtoniennes de la lumiere et de la pesanteur. (shrink)

In the histories of science, technology and aviation Christiaan Huygens has been unjustly neglected. Documents in the corpus of his works show a life-long interest in the problem of human flight together with some considerable anticipations of, and contributions to, its solution. He was among the first, if not the first, in perceiving the potential of the heavier-than-air approach. He clearly recognized the need for a powerful, mechanical motive source. He stated the first laws of aerodynamics and conceived the (...) modern propeller for propulsion. He was the first to conceive of the aeroplane. His approach to the problem of flying was both global and scientific. (shrink)

In 1665, in a response to a question posed by Robert Boyle, Spinoza gave a definition of the coherence between bodies in the universe that seems to be inconsistent both with what he had written in a previous letter to Boyle (1661) and with what he would later write in his main work, the Ethics (1677). Specifically, Spinoza’s 1665 letter to Boyle asserts that bodies can adapt themselves to another body in a non-mechanistic way and absent the agency of an (...) external cause. This letter – Letter 32 – seems, therefore, to be in clear contradiction with the metaphysical determinism that is an important and characteristic element of his philosophy. This article suggests that the viewpoint expressed by Spinoza in Letter 32 may have been inspired by a spectacular discovery made by Christiaan Huygens a few months prior, namely, the self-synchronization of pendulum clocks. As I argue in this article, this new, hypothesized link to Huygens’ pendulum experiments may account for Spinoza’s otherwise paradoxical answer to Boyle in Letter 32. (shrink)

A letter written by Christiaan Huygens to David Gregory is published here for the first time. After an introduction about the contacts between the two correspondents, an annotated English translation of the letter is given. The letter forms part of the wider correspondence about the ‘new calculus’, in which L'Hospital and Leibniz also participated, and gives some new evidence about Huygens's ambivalent attitude towards the new developments. Therefore, two mathematical passages in the letter are discussed separately. An appendix contains (...) the original Latin text. (shrink)

Ever since they began to take an interest in lens grinding, the brothers Christiaan and Constantijn Huygens searched for high-quality glass to turn in to lenses. Historical research in combination with optical measurements on preserved lenses has allowed the verificationof the lenses ground by the brothers, and also provided information on who helped them with the necessary knowledge and material.

Ever since they began to take an interest in lens grinding, the brothers Christiaan and Constantijn Huygens searched for high-quality glass to turn in to lenses. Historical research in combination with optical measurements on preserved lenses has allowed the verificationof the lenses ground by the brothers, and also provided information on who helped them with the necessary knowledge and material.

(1999). A Longitude Timekeeper by Isaac Thuret with the Balance Spring Invented by Christiaan Huygens. Annals of Science: Vol. 56, No. 4, pp. 379-394.

In 1672, inspired by the wave theory of Ignace Gaston Pardies, Christiaan Huygens made his first attempt to explain the sine law of refraction, but in 1673 he abandoned his plans owing to difficulties concerning double refraction. Huygens was able to explain double refraction on 6 August 1677 after his discoveries of the axis of symmetry of the crystal and of ‘Huygens's principle’. On 6 August 1679, he wrote: ‘I have found the confirmation of my theory of light and (...) of refraction’, and then described an ‘experimentum crucis’ to decide between his theory and a rival hypothesis. A study of caustics may have led Huygens to the discovery of ‘Huygens's principle’. (shrink)

Résumé Célébré par la plupart de ses commentateurs pour la qualité démonstrative de ses traités, le savant Christiaan Huygens (1629-1695) présente un tout autre style dans ses écrits préparatoires. L’ambivalence entre son approche analytique, nourrie par les innovations algébriques de son époque, et l’ordre synthétique de ses publications, a entretenu une illusion persistante sur la véritable nature de son mode opératoire mathématique. L’examen de ses cahiers d’étude et de ses notes de travail montre clairement que Christiaan Huygens était (...) un adepte de la méthode de Fermat, qu’il a utilisée pour une grande variété de problèmes tout au long de sa carrière. Dans le prolongement des études de Giovanna Cifoletti sur ladite méthode et sur sa diffusion, cet article se concentre sur la place de l’oeuvre de Fermat dans le développement de l’art de l’analyse de Huygens, depuis ses premières années de formation (1645-1646) jusqu’à la publication de la Geometria (1659). (shrink)

Christiaan Huygens sketched several designs for a simple microscope in his notebooks and in letters to his brother in the course of the year 1678. In this paper the various designs are described. The differences between them mainly concern the improvement of the quality of the image and easy manipulation of the specimens. Huygens' attention to these details is discussed in relation to his own microscopical investigation of micro-organisms. Huygens' designs were widely known in the circles of the learned (...) in Paris, particularly a design characterized by a diaphragm revolver and a specimen revolver. This design was adopted by several instrument makers, who copied the basic construction but changed the appearance. This study substantiates Huygens' influence on the development of contemporary simple microscopes. Moreover, Huygens' approach to the subject of the microscope and microscopy is a good example of the way he usually worked. (shrink)

When Christiaan Huygens prepared the 1686/1687 expedition to the Cape of Good Hope on which his pendulum clocks were to be tested for their usefulness in measuring longitude at sea, he also gave instructions to Thomas Helder to perform experiments with the seconds-pendulum. This was prompted by Jean Richer's 1672 finding that a seconds-pendulum is 1 1/4 lines shorter in Cayenne than in Paris. Unfortunately, Helder died on the voy¬age, and no data from the seconds-pendulum ever reached Huygens. He (...) nevertheless did receive data from his clocks on the return-voyage from the Cape of Good Hope to Texel. When he first calculated the ship's course according to these data, it appeared to have gone straight through Ireland. He then tried introducing a correction to the data, based on an idea he had previously entertained as a possible explanation of Richer's finding: he corrected the observed time to com¬pen¬sate for a reduction in the effect of gravity from the Poles to the Equator resulting purely from the Earth's rotation. His newly calculated course convinced him that this rotational effect is the sole source of any variations in gravity with latitude. This paper examines Huygens's correc¬tions to the data and his reasoning from the new course to the conclusion that nothing else causes a variation in gravity. In the process, we show that Huygens had cogent empirical reasons to reject Isaac Newton's theory of universal gravity, which predicted a some¬what larger variation in gravity. (shrink)

ABSTRACTThis paper deals with the book Cosmotheoros, in which Christiaan Huygens presented his concept of a universe made up of many inhabited planets. Recent interpreters of this work have focused especially on cosmological issues presented in the book. Cosmotheoros, however, comprises also various philosophical ideas. In this paper I want to focus on the concept contemplator coeli – stargazer. The stargazer was the embodiment of the philosophical ideal of the contemplative way of life that appeared in classical philosophy and (...) astronomy. I want to argue that Huygens followed on from the idea of the stargazer and used it in his hypothetical construction of extra-terrestrial life. At the same time, however, he altered this idea in such a way that it corresponded better to the ideals of science at the end of the seventeenth century. In Huygens’ concept, the noble contemplator coeli turned into the modern scientist who works with other scientists on the advancement of mankind’s knowledge of nature. Huygens’ stargazers are a good example of how strikingly the basic assumptions of knowledge of nature in the early modern period changed with regard to classical antiquity. (shrink)

Summary Until recently it was believed that Christian Huygens’ earliest publication of his pendulum invention was Horologium of 1658. He published the more famous general treatise, Horologium Oscillatorium, fifteen years later in 1673. Two years ago, an article1 suggesting an unknown collaboration in developing the clock pendulum between Huygens and the Paris clockmaker Isaac Thuret, presented the evidence of Benjamin Martin, an 18th century educationalist and retailer of scientific material. Martin described a Huygens publication of 1657 and reproduced the illustration (...) it contained. This illustration shows a different clock from the one drawn in Horologium and different also from those previously considered as Huygens’ earliest surviving examples. However, the illustration is similar to part of a plate in Horologium Oscillatorium and this similarity caused one historian to cast doubt on the existence of the 1657 publication.2 This article, with information presented for the first time, seeks to prove the existence of that work and thereby establish it in the canon of Huygens’ writings while re-examining the invention in the light that it casts. 1Whitestone, Sebastian, ‘The Identification and Attribution of Christiaan Huygens’ First Pendulum Clock', Antiquarian Horology, December (2008), 201–222. 2Plomp, R., ‘Letter', Antiquarian Horology, December (2009), 714–17. See also author's reply, ibid, 717–19. (shrink)

Both before and after the publication of Isaac Newton’s particulate theory of light, numerous wave theories of light were advanced by both philosophers and scientists (e.g., René Descartes, Thomas Hobbes, Robert Hooke, Francesco Grimaldi, and Christiaan Huygens). What is peculiar about this list, as frequently found in the scholarly literature on light, is that it refers to individuals who do not extend much further back than the seventeenth century. A close examination of Aristotle’s account of color and light in (...) comparison to Christiann Huygens’ theory of color and light, however, reveals that Aristotle deserves to be recognized as one who antedates and foreshadows these modern wave theorists. Indeed, we shall argue that Aristotle offered the first wave theory of color and light. On Aristotle’s theory, light is the actualization of a transparent medium such as air or water that makes possible the dissemination of color through the medium in a manner analogous to the dissemination of sound through air or water. (shrink)

In 1662 Christiaan Huygens carried out the famous Torricelli experiment to test the existence of atmospheric pressure by inserting the apparatus in the glass receiver of a vacuum pump, and evacuating the air inside it. He reported that when the air was exhausted, a column of water remained suspended in a 4-foot tube. This unexpected result was in stark contrast with earlier experiments of Boyle and Hooke that apparently had confirmed Torricelli’s explanation that such a water column was supported (...) by outside air pressure, and would fall when the air was removed. Huygen’s “anomalous suspension” led to the continuation of controversies in the seventeenth century about the nature of the vacuum that these experiments were expected to resolve. Surprisingly, the origin of Huygens’ unexpected result has remained a puzzle up to the present time. In this paper, I discuss the dynamics of such a column of water under the experimental conditions reported by Boyle and by Huygens, that turned out to be different, and present the results of a replication of their experiments with a modern vacuum pump. Contrary to the conventional explanations of these experiments, I demonstrate that in the Boyle–Hooke version of this experiment, the water column descends initially because it is forced down by the gas pressure due to air dissolved in the water which is released inside the Torricelli tube after the external pressure is sufficiently decreased. Huygens, however, first removed this trapped air before he carried out his experiment. In the absence of this internal gas pressure, the early rudimentary vacuum pumps were inadequate to decrease the air pressure sufficiently inside the receiver to demonstrate the descent of a Torricelli column of airless water 4-foot in height or less. (shrink)

The Royal Society possesses three long-focus simple lenses of diameters 195, 210 and 230 mm, all inscribed with the signature ‘C. Huygens’ and various dates in the year 1686. These prove to have been made by Constantine Huygens, the elder brother of the famous Christiaan Huygens. All three lenses have been examined by a variety of physical and chemical methods, both to define their optical characteristics and to establish the composition of dated samples of late-seventeenth-century Continental glass. The focal (...) lengths of 37·9, 50·1 and 65·2 metres found by combination agree with Huygens' own values of 122, 170 and 210 feet respectively, and are so great that practical employment of the lenses in aerial telescopes has rarely been achieved. All are made from the same very poor glass—a heterogeneous and discoloured potash-rich ‘forest glass’—with a refractive index of 1·516, a costringence of 60, and a density of 2·5 g cm−3. The three lenses were ground with just two concave laps, of radii of curvature 27·11 and 71·15 metres, one lens being plano-convex to a high degree of accuracy. A claim by previous investigators that one lens was a ‘light flint’ glass has been disproved. (shrink)

Quels furent les relations de Christiaan Huygens avec les chimistes qu'il eut l'occasion de fréquenter pendant son séjour parisien? A l'examen, elles furent moins distantes que ne le laissent supposer les quelques déclarations fracassantes qui parsèment sa correspondance. Néanmoins, il est difficile d'affirmer qu'il y eut, entre Huygens et la pensée chimique en général, une sympathie qui aurait pu aller au-delà des rencontres individuelles.

The concept of mechanistic philosophy dates back to the beginning of the early modern period. Among the commonalities that some of the conceptions of the main contemporary representatives share with those of the leading early modern exponents is their ontological classification: as regards their basic concepts, both contemporary and early modern versions of mechanism can be divided into monist and dualist types. Christiaan Huygens’ early modern mechanistic explanation of non- material forces and Stuart S. Glennan’s contemporary conception of mechanism (...) will serve as examples of monism. As examples of dualism, I will discuss Isaac Newton’s early modern mechanistic philosophy of nature and the contemporary conception of mechanism proposed by Peter Machamer, Lindley Darden, and Carl F. Craver. With the ontological commonalities are associated further characteristic features of the respective types that concern, among other things, the respective understandings of fundamental theories and evaluations of scientific practice. The ontological continuity Of the types does not play any role in contemporary discussions of the history of mechanistic philosophy. On my assessment the distinction between monism and dualism remains an unsolved problem and its persistence is an indication that this distinction is a fundamental one. (shrink)