Later philosophers banish the consideration of such a cause out of natural philosophy, feigning hypotheses for explaining all things mechanically and referring other causes to metaphysics: whereas the main business of natural philosophy is to argue from phenomena without feigning hypotheses and to deduce causes from effects till we come to the very first cause, which certainly is not mechanical; and not only to unfold the mechanism of the world, but chiefly to resolve these and such like questions. What is there in places almost empty of matter and whence is it that the sun and planets gravitate toward one another without dense matter between them? Whence is it that nature does nothing in vain; and whence arises all that order and beauty which we see in the world? To what end are comets, and whence is it that planets move all one and the same way in concentric orbits, while comets move all manner of ways in orbits very eccentric, and what hinders the fixed stars from falling upon one another? Does it not appear from phenomena that there is a Being incorporeal, living, intelligent, omnipresent, who in infinite space, as it were in his sensory, sees the things themselves intimately?" and so on.

In the twenty-ninth query, Newton 16 proceeded to develop his own emission-theory of light. It begins:

"Are not the rays of light very small bodies emitted from shining substances? For such bodies will pass through uniform mediums in right lines without bending into the shadow, which is the nature of the rays of light. They will also be capable of several properties and be able to conserve their properties unchanged in passing through several mediums, which is another condition of the rays of light."

"It is remarkable," said Rosenberger," "that the state

"Horsley, Vol. IV, pp. 238-241. Cf. Rosenberger, op. cit., pp. 319-321. "Op. cit., pp. 320-321.

ment [in this query] of the necessity of attractive forces and [in the preceding one] of the impossibility of an ether is followed by a reference intercalated in the edition of 1717, to the derivation of this attraction by means of this ether. This reference is: 'What I mean in this question by a vacuum and by the attraction of the rays of light towards glass or crystal may be understood by what was said in the 18th, 19th, and 20th questions.'18 Apparently Newton wished to show, even in his queries, that his theories are reconcilable with all hypotheses. ...'

It is obviously incorrect to speak, as Rosenberger does, of Newton's "statement...of the impossibility of an ether." As a rule, we have no means of deciding, from the "Queries," what Newton's real opinions on an ether were; but the letters to Bentley throw a great deal of light on the subject. Indeed, the weight of evidence seems to tell against Rosenberger's19 view and in favor of the view which has become traditional, that Newton believed in some sortnot the Cartesian-of ether on the ground that he could not imagine a propagation of force without a medium.2

20

The thirtieth query21 begins: "Are not gross bodies and light convertible into one another; and may not bodies receive much of their activity from the particles of light which enter their composition?" We know that for long after this, the matter of light was considered as a possible part of the subject-matter of chemistry.

The thirty-first query22 was greatly added to in later editions, but we will here collect all that is said in it in its final form about the subjects that interest us at present. It begins:

"Have not the small particles of bodies certain powers,

"Horsley, Vol. IV, p. 241. These queries are given in § IV below. "Cf. also op. cit., pp. 333-334.

Cf. § VI below.

"Horsley, Vol. IV, pp. 241-242. Cf. Rosenberger, op. cit., pp. 321-322.

*Horsley, Vol. IV, pp. 242-264. Cf. Rosenberger, op. cit., pp. 322-327.

virtues or forces by which they act at a distance, not only upon the rays of light for reflecting, refracting and inflecting them, but also upon one another for producing a great part of the phenomena of nature? For it is well known that bodies act one upon another by the attractions of gravity, magnetism and electricity, and these instances show the tenor and course of nature and make it not improbable that there may be more attractive powers than these. For nature is very consonant and conformable to herself. How these attractions may be performed, I do not here consider. What I call attraction may be performed by impulse or by some other means unknown to me. I use that word here to signify only in general any force by which bodies tend toward one another, whatever be the cause. For we must learn from the phenomena of nature what bodies attract one another and what are the laws and properties of the attraction, before we inquire the cause by which the attraction is performed. The attractions of gravity, magnetism and electricity reach to very sensible distances and so have been observed by vulgar eyes, and there may be others which reach to so small distances as hitherto escape observation; and perhaps electrical attraction may reach to such small distances even without being excited by friction."

"All bodies," said Newton,23 "seem to be composed of hard particles." And again:24 ..it seems probable to me that God in the beginning formed matter in solid, massy, hard, impenetrable, movable particles of such sizes and figures and with such other properties and in such proportion to space25 as most conduced to the end for

24

Ibid., pp 260-262.

"Horsley, Vol IV, p. 251. "Eoque numero et quantitate pro ratione spatii in quo futurum erat ut moverentur. Dr. Clarke's first Latin; and so the sentence stands in Dr. Clarke's second Latin edition, which in most places was so corrected as to agree exactly with the second English. And to make sense of the passage, something is evidently wanting here to answer to the words of the Latin, in quo futurum erat ut moverentur. For to speak of particles of matter as bearing proportion to space indefinitely were absurd."-Note by Horsley.

which he formed them, and that these primitive particles being solids, are incomparably harder than any porous bodies compounded of them; even so very hard as never to wear or break in pieces; no ordinary power being able to divide what God himself made one in the first creation. While the particles continue entire, they may compose bodies of one and the same nature and texture in all ages; but should they wear away or break in pieces, the nature of things depending on them would be changed. Water and earth composed of old worn particles and fragments of particles would not be of the same nature and texture now with water and earth composed of entire particles in the beginning. And therefore that nature may be lasting, the changes of corporeal things are to be placed only in the various separations and new associations and motions of these permanent particles; compound bodies being apt to break, not in the midst of solid particles but where those particles are laid together and only touch in a few points.

"It seems to me further that these particles have not only a vis inertiae accompanied with such passive laws of motion as naturally result from that force, but also that they are moved by certain active principles, such as is that of gravity and that which causes fermentation and the cohesion of bodies. These principles I consider not as occult qualities, supposed to result from the specific forms of things, but as general laws of nature by which the things themselves are formed: their truth appearing to us by phenomena, though their causes be not yet discovered. For these are manifest qualities, and their causes only are occult. And the Aristotelians gave the name of occult qualities not to manifest qualities but to such qualities only as they supposed to lie hid in bodies and to be the unknown causes of manifest effects: such as would be the causes of gravity and of magnetic and electric attractions and of

fermentations, if we should suppose that these forces or actions arose from qualities unknown to us and incapable of being discovered and made manifest. Such occult qualities put a stop to the improvement of natural philosophy, and therefore of late years have been rejected. To tell us that every species of things is endowed with an occult specific quality by which it acts and produces manifest effects, is to tell us nothing: but to derive two or three general principles of motion from phenomena, and afterwards to tell us how the properties of motion follow from phenomena, and afterwards to tell us how the properties and actions of all corporeal things follow from those manifest principles, would be a very great step in philosophy, though the causes of those principles were not yet discovered. And therefore I scruple not to propose the principles of motion above mentioned, they being of very general extent, and leave their causes to be found out.

"Now by the help of these principles, all material things seem to have been composed of the hard and solid particles above mentioned, variously associated in the first creation by the counsel of an intelligent Agent. For it became Him who created them to set them in order. And if he did so, it is unphilosophical to seek for any other origin of the world or to pretend that it might arise out of a chaos by the mere laws of nature; though being once formed, it may continue by those laws for many ages. For while comets move in very eccentric orbits in all manner of positions, blind Fate could never make all the planets move one and the same way in orbits concentric, some inconsiderable irregularities excepted, which may have arisen from the mutual actions of comets and planets upon one another, and which will be apt to increase till this system wants a reformation. Such a wonderful uniformity in the planetary system must be allowed the effect of choice. And so must the uniformity in the bodies of animals."