NEWTON, ISAAC (b. Woolsthorpe, England, 25 December 1642; d. London, England, 20 March 1727), mathematics, dynamics, celestial mechanics, astronomy, optics, natural philosophy.

    Space, one of which acts upon the other, and by consequence is re-acted upon, without retarding, shattering, dispersing and compounding one another's Motions.”

In query 30, Newton discussed the convertibility of gross bodies and light, with examples showing that nature delights in transmutations. In illustration, he cited Boyle's assertion that frequent distillations had turned water into earth. In query 31, he discussed questions ranging from the forces that hold particles of matter together to the impact of bodies on one another; also causes of motion, fermentation, the circulation of the blood and animal heat, putrefaction, the force of inertia, and occult qualities. He stated a general philosophy and concluded with the pious hope that the perfection of natural philosophy will enlarge the “Bounds of Moral Philosophy.”

Newton's queries, particularly the later ones, thus go far beyond any simple questions of physical or geometrical optics. In them he even proposed tentative explanations of phenomena, although explanations that are perhaps not as fully worked out, or as fully supported by experimental evidence, as he might have wished. (Some queries even propose what is, by Newton's own definition, a hypothesis.) In each case, Newton's own position is made clear; and especially in the queries added in the Latin version of 1706 (and presented again in the English version of 1717/1718), his supporting evidence is apt to be a short essay.

One notable development of the later queries is the emphasis on an “Aethereal Medium” as an explanation for phenomena. In his first papers on optics, in the 1670's, Newton had combined his cherished conception of corpuscular or globular light with the possibly Cartesian notion of a space-filling ether, elastic and varying in density. Although Newton had introduced this ether to permit wave phenomena to exist as concomitants of the rays of light, he also suggested other possible functions for it—including causing sensation and animal motion, transmitting radiant heat, and even causing gravitation. His speculations on the ether were incorporated in the “Hypothesis” that he sent to the Royal Society (read at their meetings in 1675 and 1676) and in a letter to Boyle of 28 February 1679.168

In the second English edition of the Opticks (1717/1718) Newton made additions which “embodied arguments for the existence of an elastic, tenuous, aetherial medium.” The new queries in the Latin version of 1706 did not deal with an ether, however, and by the time of the Principia, Newton may have “rejected the Cartesian dense aether” as well as “his own youthful aetherial speculations.”169

Newton thus did not propose a new version of the ether until possibly the 1710's; he then suggested, in the general scholium at the conclusion of the second edition of the Principia (1713), that a most subtle “spiritus” (“which pervades and lies hid in all gross bodies”) might produce just such effects as his earlier ether (or the later ethereal medium of queries 18 through 24). In the general scholium of the Principia, however, Newton omitted gravitation from the list of effects that the “spiritus” may produce. There is evidence that Newton conceived of this “spiritus” as electrical, and may well have been a precursor of the ether or ethereal medium of the 1717/1718 queries.170 In a manuscript intended for the revised second English edition of the Opticks,171 Newton wrote the heading, “The Third Book of Opticks. Part II. Observations concerning the Medium through which Light passes, & the Agent which emits it,” a title that would thus seem to link the ethereal medium with the emission of electrical effluvia. It would further appear that Newton used both the earlier and later concepts of the ether to explain, however hypothetically, results he had already obtained; and that the concept of the ether was never the basis for significant new experiments or theoretical results. In a general scholium to book II, Newton described from memory an experiment that he had performed which seemed to him to prove the nonexistence of an ether; since Newton's original notes have never been found, this experiment, which was presumably an important element in the decline of his belief in an ether, cannot be dated.

The later queries also develop a concept of matter, further expounded by Newton in his often reprinted De natura acidorum (of which there appear to have been several versions in circulation).172 Newton here, as a true disciple of Boyle, began with the traditional “mechanical philosophy” but added “the assumption that particles move mainly under the influence of what he at first called sociability and later called attraction.”173 Although Newton also considered a principle of repulsion, especially in gases, in discussing chemical reactions he seems to have preferred to use a concept of “sociability” (as, for example, to explain how substances dissolve).

He was equally concerned with the “aggregation” of particles (in queries 28 and 31 as well as at the end of De natura acidorum) and even suggested a means of “differentiating between reaction and transmutation.”174 Another major concern was the way in which aqua regia dissolves gold but not silver, while aqua fortis dissolves silver but not gold,175 a phenomenon Newton explained by a combination of the attraction of particles and the relation between