John C. Henry

ABSTRACT As well as the mathematically-supported celestial mechanics that Newton developed in his Principia, Newton also proposed a more speculative natural philosophy of interparticulate forces of attraction and repulsion. Although this speculative philosophy was not made public before the ‘Queries’ which Newton appended to the Opticks, it originated far earlier in Newton’s career. This article makes the case that Newton’s short, unfinished manuscript, entitled ‘De Aere et Aethere’, should be seen as an important landmark in Newton’s intellectual development, being the first work in which Newton assumed there are repulsive forces operating at a distance between the particles of bodies. The article offers an account of how Newton came to write ‘De Aere et Aethere’ and why. It also outlines its relationship to the ‘Conclusio’, with which Newton briefly intended to finish the Principia, and to the ‘Queries’ in the Opticks. The date of the manuscript is disputed, and the article also aims to settle this dispute. Claims that the ‘De Aere et Aethere’ must have been written before the ‘Hypothesis... of Light’ of 1675 are dismissed, and it is suggested, following R. S. Westfall, that it was written after a well-known letter Newton wrote to Boyle early in 1679.

ArgumentIt is argued that the sensorium of God was introduced into theQuaestionesadded to the end of Newton’sOptice(1706) as a way of answering objections that Newton had failed to provide a causal account of gravity in thePrincipia. The discussion of God’s sensorium indicated that gravity must be caused by God’s will. Newton did not leave it there, however, but went on to show how God’s will created active principles as secondary causes of gravity. There was nothing unusual in assuming that God, acting as the First Cause, operated in nature by means of secondary causes; but it was unusual to devote as much time to discussing God’s precise role as to discussing the secondary causes themselves. It is contended that Newton felt the need to do this to persuade readers that what might seem like a second cause that could not possibly work could be made to work by the omnipotent God.

This paper is in three sections. The first establishes that Newton, in spite of a well-known passage in a letter to Richard Bentley of 1692, did believe in action at a distance. Many readers may see this merely as an act of supererogation, since it is so patently obvious that he did. However, there has been a long history among Newton scholars of allowing the letter to Bentley to over-ride all of Newton’s other pronouncements in favour of action at a distance, with devastating effects on our understanding of related aspects of his physics and his theology. Furthermore, this misconceived scholarly endeavour shows no sign of abating. The second section then offers a historical reconstruction, based on Newton’s writings, of how, when and why he began to accept actions at a distance and make them one of the cornerstones of his physics. Finally, using this chronological account of Newton’s use of actions at a distance, the paper re-assesses the claims of B. J. T. Dobbs that Newton’s important manuscript, De gravitatione et aequipondio fluidorum, was written, not in the late 1660s or early 1670s as was previously supposed, but during the composition of the Principia, in 1684 or 1685.Keywords: Isaac Newton; Action-at-a-distance; Gravity; Force; Aether; Attraction.

This chapter focuses on the English response to Thomas Hobbes as a mechanical philosopher. Hobbes's mechanical philosophy was by no means merely derivative from Descartes's Principia philosophiae; indeed, Hobbes came closer than anyone else to developing a mechanistic system to match it. Hobbes's system was a carefully thought‐out and uniquely original system of mechanical philosophy, and none of his contemporaries, not even his staunchest critics, ever considered it to be simply derived from Cartesianism. An important aspect of the dispute between Robert Boyle and Hobbes was concerned with the correct method to arrive at knowledge of the natural world. The distinctions between the thought of Hobbes and his critical contemporaries were by no means as stark as his critics wanted to maintain, but were highly nuanced. This can be seen in the marked similarity between Hobbes's concept of a corporeal God, and Henry More's influential concept of a supposedly immaterial but nonetheless three‐dimensionally extended God.

In lieu of an abstract, here is a brief excerpt of the content:Journal of the History of Ideas 62.1 (2001) 99-119 [Access article in PDF] Animism and Empiricism: Copernican Physics and the Origins of William Gilbert's Experimental Method John Henry In the second year of this journal's run, way back in 1941, appeared Edgar Zilsel's classic and still widely cited paper on The Origins of William Gilbert's Experimental Method. 1 Focusing on Gilbert's De magnete of 1600, undoubtedly a seminal text in the history of the experimental method, 2 Zilsel argued that Gilbert borrowed his methodology from elite craftsmen, artisans, and other manual workers involved in mining, smelting, smithing, compass making, navigation, sailing, and other activities which involved working with iron or with magnets. 3 On its appearance the paper contributed to a growing and still continuing debate in the history of science about the relative importance of scholars and craftsmen in the origins of modern science. Although Zilsel's general thesis has been critically evaluated in terms of that wider debate, 4 his very specific claims about the [End Page 99] role of elite craftsmen in providing Gilbert with a ready-made experimental method, have never been properly considered. This paper attempts to reassess Zilsel's claims about the origin of Gilbert's experimental method and, in so doing, to arrive at a richer understanding of what Gilbert was trying to do in De magnete and to suggest an alternative source for his experimentalism.The first thing to note about Zilsel's argument is that it had two strands. 5 One of these pointed to actual experimental techniques used by Gilbert and showed that they can all be found in earlier writings on magnets. To be more specific, the techniques in question are to be found either in the thirteenth-century "Letter on the Magnet" written by Petrus Pergrinus or Pierre de Maricourt, first published in 1558, or in The Newe Attractive, a work on the magnetic compass written by a retired mariner, Robert Norman, first published in 1581 but reprinted three times before 1600. 6 The second strand did not involve experiments at all, with one notable exception, but simply implied or suggested that Gilbert's experimental techniques must have been inspired by miners and foundrymen, or navigators and instrument makers. The problem here, as others have objected, 7 is that it is by no means clear that elite craftsmen were engaged in performing experiments in anything like the sense of the word required for the argument to cut any ice. For Zilsel, however, "we cannot doubt that many of [the miners and foundrymen of the period], stimulated to improvements by economic competition, were wont to try new techniques and to observe natural processes." 8 A few sentences later we are told that it is "obvious" that "among such manual labourers there were experimentalists, though experimentalists with practical aims only and without theoretical knowledge." 9 [End Page 100]The philosopher of science at this point might legitimately want to suggest that an experiment is not an experiment unless it is testing a theory, but we do not have to enter into such arguable niceties. 10 We can see that there is something profoundly tendentious in Zilsel's claims simply by reading on. At this point Zilsel mentioned the only experiment specifically referred to in this strand of his argumentation. Quoting Gilbert, Zilsel showed that Gilbert himself must have descended into a mine in order, as Zilsel says, "to verify the hypothesis" that the polarity of a magnet derives from the polarity of the earth: We had a twenty pounds' heavy loadstone dug and hauled out after having first observed and marked its ends in its vein. Then we put the stone in a wooden tub on water, so that it could turn freely. Immediately the surface which had looked to the North in the mine turned itself to the North on the water. 11Zilsel did not make the absurd claim that Gilbert must have seen miners doing this kind of experiment, but he did all he could to...

Samuel Clarke is best known to historians of science for presenting Isaac Newton’s views to a wider audience, especially in his famous correspondence with G. W. Leibniz. Clarke’s independent writings, however, reveal positions that do not derive from, and do not coincide with, Newton’s. This essay compares Clarke’s and Newton’s ideas on the cause of gravity, with a view to clarifying our understanding of Newton’s views. There is evidence to suggest that Newton believed God was directly responsible for gravity, and this interpretation has been promoted by a number of scholars. By comparing Newton’s views with those of Clarke, however, it can be seen that Newton did not subscribe to the kind of occasionalist approach to gravity that Clarke developed. Clarke insisted that matter was categorically incapable of being endowed with powers or forces and that therefore what looks like gravitational attraction has to be performed directly by God or by angels. By comparing Clarke’s pronouncements with Newton’s, it becomes clear that Newton adopted the more standard line: that the first cause, God, operated in nature through secondary causes and that gravitational attraction was just such a secondary (albeit occult) cause.

La acción a distancia se ha considerado muy a menudo como un medio de explicación inaceptable en la física. Debido a que daba la impresión de resistirse a los intentos de asignarle causas propias a los efectos, la acción a distancia se ha proscrito como sinsentido ocultista. El rechazo de la acción a distancia fue el principal precepto del aristotelismo que fue tan dominante en la filosofía natural europea, y hasta hoy permanece como un prejuicio principal de la física moderna. No obstante, hubo un período de interregno; un período durante el cual las acciones a distancia eran fácilmente aceptadas por un número ignificativo de filósofos naturales. La principal influencia sobre este nuevo enfoque radical hacia la naturaleza de la causalidad física fue, por supuesto, Isaac Newton. El principio de gravitación universal de Newton a muchos les pareció dar no sólo un ejemplo innegable de una fuerza cuya naturaleza no se podía producir por ningún tipo de contacto mecánico entre los cuerpos, sino también un modelo para otras supuestas fuerzas que podían suponerse que dan cuenta de los fenómenos químicos, biológicos y otros fenómenos físicos. Por tanto, durante el siglo XVIII, como lo han demostrado un gran número de importantes estudios históricos, los filósofos naturales buscaron hacer fructífero el deseo de Newton, expresado en el Prefacio a los Principia, de que todos los fenómenos de la naturaleza fueran explicados en términos de fuerzas atractivas y repulsivas que operan a distancia entre las partículas diminutas de los cuerpos. Sin embargo, en la actualidad el rechazo a la legitimidad de las acciones a distancia es tan grande que una serie de notables especialistas de Newton han insistido en que Newton nunca creyó en la actio in distans y que fue completamente malentendido por la generación que le sucedió. Este artículo reitera que Newton sí creía en la acción a distancia y refuta los argumentos de especialistas recientes que sostienen lo contrario.

Una de las principales razones para el éxito de la filosofía natural de Newton fue el papel que ésta tuvo al desarrollar una teología natural valiosa. Además, Newton mismo publicó las implicaciones teológicas de su propia filosofía natural. Aunque en la primera edición de los Principia no hay ninguna señal de Dios, para la segunda edición (1713) Newton introdujo un "Escolio General" en el que explícitamente discutía la relación entre Dios y su Creación. La obsesión de Newton por la interpretación de las Escrituras durante algún tiempo fue desestimada como embarazosa. Sin embargo, su importancia para una comprensión adecuada de Newton ahora se reconoce y estimula mucha actividad nueva entre los especialistas. El significado de este trabajo permite ver en la actualidad el núcleo de la pregunta de Richard H. Popkin: “¿por qué uno de los más grandes teólogos anti-Trinitarios se dedicó a escribir obras de filosofía natural, como los Principia Mathematica?