[Margin: Aristotle’s 1st Argument against the Earth’s motion.]
[I.] When Aristotle (On the Heaven, bk. 2, ch. 12) had reproved certain of the Ancients — especially Anaximander, who, anxious as to why the whole Earth is not borne downward but rests at the center of the World, had rendered no reason from the Earth’s own nature, nor [explained] why its parts are borne toward the middle of the world — he himself laid down that it must first be asked whether [the Earth] is moved, and then where it rests. Wherefore, in ch. 13, text 96, he tries to show that the earth, by its own nature, is moved by neither motion; for, repeating what he had narrated in ch. 13, he says: For, as we said, some make it [the Earth] to be one of the stars; others, placing it in the middle, say that it is turned and moved about the middle and about its own poles. And at once he subjoins: But that this is impossible is manifest, the principle being assumed: that if it is borne — whether existing in the middle, or outside the middle — it is necessary that it be moved violently by this motion; for it is not [the motion] proper to the Earth itself, for then each one of its particles would have this same motion; but now they are all borne in a straight line toward the middle. Wherefore, since this motion is violent, or beside nature, it is not possible that it be everlasting; but the order of the World is everlasting. His argument, then, reduced to the syllogistic rules, is of this kind.
[…continues on p. 437 (PDF 472) with the catchword “I. Ar-” (I. Argumentum) — the sub-head “I. Aristotle’s Argument from the Violence of the motion,” and its formal syllogism.]
(printed p. 437 — within Chapter XXIV: Aristotle’s First Argument, from the violence of the motion (a circular motion of the whole Earth would be violent and so not everlasting), is set out in form with the Copernican responses. Then the Second and Third Arguments reproduce Scheiner’s sorites from the Mathematical Disquisitions, answered by Galileo: the first two of his three Enthymemes (on the abolition of simple straight motion and the unassignable principle of the motion) are reported with the Copernican replies, the third beginning.)
[Header: DE SYSTEMATE TERRÆ MOTÆ — 437]
I. Aristotle’s Argument, from the Violence of the motion
[Margin: 1st Argument’s Form.]
[II.] If the whole Earth were moved — either by the annual and diurnal [motions] together, or by the diurnal motion alone — its motion would be violent or preternatural; but a violent or preternatural motion ought not to be attributed to the whole Earth. Therefore, etc.
The Major is proved, because neither motion would be from the Earth’s own natural principle; for if a circular motion — whether of translation [revolution], or of the whirling alone — were natural to the whole Earth, it would be natural to its parts too. But it is not natural to the Earth’s parts; therefore neither to the whole Earth. That it is not natural to the parts is proved, because not all [the parts] are moved circularly, whether by whirling or by translation, but, when let go, are borne downward along a straight line perpendicular to the middle. The Minor is proved, because a motion which is not everlasting ought not to be attributed to the Earth (which is a part of the World), since the order of the World in its other parts and motions — namely in the heaven of the world, in generations, etc. — is everlasting; but if a violent or preternatural motion were attributed to the Earth, it would not be everlasting, for nothing violent is perpetual.
[Margin: 1st Response to the 1st Argument.]
The Copernicans will respond, first, by denying the Major; to whose proof they will concede that the circular motion is natural both to the whole Earth and to its parts, so long as the parts are conjoined with their whole; but if separated, they will say that the natural [motion] for them is a motion mixed of the circular and the straight, or some other similar [motion], according to the figure of motion required — so that, by tending downward, they fall back onto the point of the Earth above which they were let go perpendicularly (concerning which, enough in ch. 17). But when it is said, in the proof of the Major, that a circular or quasi-circular motion does not belong to the parts, this they will deny; and as to the proof of that statement drawn from the apparent straightness of the downward motion of heavy bodies, they will concede that their motion apparent to us is rectilinear, but will deny [it] of the real motion, which takes place in the cosmic space.
[Margin: Objection against the Response.]
Against which response, nevertheless, the Aristotelians will press that it is absurd to desert the sense, and in Physics to destroy a motion which appears, in order that there be substituted a motion which neither appears nor can appear — and that for the sake of certain reasons [that are] fitting, but by no means necessary.
[Margin: 2nd Response to the Argument.]
The Copernicans will respond, secondly, to the Minor, by denying it as to its second part, concerning preternatural motion; or they will turn the argument back upon Aristotle, who attributes to fire a circular motion from without (on account of the diurnal conversion of the heaven) — and therefore preternatural, yet perpetual. A circular motion, then, can be attributed to the earth’s parts too, if they are drawn magnetically by the whole globe of the Earth (as Gilbert, Kepler, Galileo, Gassendi judge); indeed even to the whole Earth, if this too is drawn into a gyre by the Sun’s whirling about its own center (as Kepler judges).
II. Argument, from the Simplicity of motion due to the Earth
[III.] Our [Father Christoph] Scheiner uses a very long Sorites and heaped-up interrogations in the Mathematical Disquisitions, from page 31 to 35; to which Galileo tries to respond (Dialogue 2, from the Latin page 175 to 182, but from the Italian 232 to 240). But since Scheiner at length (page 35) gathers into three Enthymemes what he had said before, I shall report those in order, with the responses which Galileo (partly) and other Copernicans (partly) have suggested from their hypotheses. His first argument is of this kind.
[Margin: Scheiner’s 1st Enthymeme against the Earth’s motion.]
The Copernican motion of the Earth takes away from the Universe the simple motion of things, upward and downward; therefore it is not to be admitted.
The Antecedent is clear, because from the Copernican motion of the Earth it is necessary that heavy and light bodies naturally so descend or ascend to their place that they describe a line not indeed perfectly circular, but quasi-circular and varied (according to the different parallels), as is clear from the figures adduced in ch. 17, nos. 16, 17, 18. The Consequence is proved, because it is evident, from the perpetual experience of the senses, that to heavy and light bodies there belongs a simple motion along a straight line upward and downward, falling perpendicularly upon the Earth.
The Copernicans respond by denying the Antecedent. As to the motion apparent and evident to sense, the Copernican hypothesis too represents this as rectilinear — in which sense they concede the Consequence; but they [take] the Antecedent [as concerning] the real line of this motion, against which there is no experience of sense, since [experience] behaves toward it merely negatively, and is borne only upon the apparent motion.
III. Argument, from the Inconveniences of the Principle of this motion, whatever that [principle] be assigned to be
[Margin: Scheiner’s 2nd Enthymeme.]
[IV.] The second argument of Scheiner (on the same page 35), which here is our third, is of this kind: The Copernican motion of the Earth necessarily induces, in all things — borne both from the center and toward the center — some circular motion, whose principle, nevertheless — whether natural or non-natural, whether internal or external — cannot be assigned without innumerable absurdities. Therefore the Earth’s motion is not to be admitted.
Yet very many of the absurdities, previously enumerated by him, militate only against an external and non-natural principle, which the better Copernicans do not assign; nor do even Kepler or others — who acknowledge magnetic attractions from the earth — suppose that the parts of the earth placed outside their own place are drawn by the terrestrial globe unnaturally, but naturally, there concurring in them an inclination to receive the attraction passively. Let us hear, then, what he brings against those who assign this principle as natural and intrinsic. He says that, if the circular motion is natural to the Earth, the straight [motion] — which at any rate appears in those [bodies] — cannot be natural, since these motions differ from one another in species. Moreover, if the whole earth with the water were annihilated, no hail or rain would fall from a cloud along an apparent straight line, but would naturally only be carried round in a circle — which he affirms to be contrary to experiments and to reason. Finally, if beneath the earth, around the Earth’s center, there were an airy sphere, and a stone were placed at the earth’s center, this [stone] ought naturally to ascend from that center to the rest of the earth, and afterward to rotate with it, so as thus to be joined to its whole and to imitate its circular motion — which likewise seems absurd, since that stone ought to remain beneath the air and at the center. Therefore the motion of the Earth, or of its parts, is not from within and natural.
[Margin: Response to argument 3.]
Galileo would nevertheless respond by denying the Antecedent; to whose proof he will say that the principle of this motion is natural and from within, and that it is not repugnant that the same be the principle of a motion really circular and apparently rectilinear — because through it [that principle] the eye too is carried round circularly, and accordingly cannot see the motion except always in the same straight line. Next, if the Terraqueous globe were annihilated, it is uncertain what miracle would occur in the rest of the elementary sphere, this miracle [of annihilation] being posited; perhaps, however, either the hail and rain would descend together with the rarefied air to fill the vacuum, or would really go round in a circle about the place in which the Earth’s globe had been; or, because they would not know that the Earth had been annihilated, would descend (just as now) all the way to that center which had previously been the Earth’s center. Finally, the rock would remain at the Earth’s center, because that is the center of Heavy [bodies], around which (or toward which) they tend, so as thus to be united to their whole — yet so that, if not impeded, they tend thither where all the parts of the globe conspire to arrange themselves equally around it. That stone, nevertheless, would be turned about its own and the Earth’s center.
IV. Argument, from the Perversion of straight terrestrial motion (held as quasi-violent) and of circular motion (as natural)
[Margin: 4th Argument, from Scheiner.]
[V.] Scheiner’s third argument, on that page 35, is of this kind: The Copernican motion of the Earth makes the straight motion accidental to heavy bodies, and quasi-violent; whereas [it makes] the circular [motion] necessary and natural; it gives to things most diverse in nature one nature of moving: it spontaneously calls forth the stone upward from the earth’s center; the same [stone it]…
[…continues on p. 438 (PDF 473) with the catchword “deci-” (deci-dere, “to fall down”) — completing Scheiner’s third Enthymeme and its Copernican answer.]
(printed p. 438 — within Chapter XXIV: Scheiner’s third Enthymeme (that the Copernican view perverts straight motion into the quasi-violent and circular into the natural) is finished and answered. Then Scheiner’s eleven little Questions about the principle of the Earth’s motion — its internal or external cause, why west-to-east only, why speeds vary with latitude, what becomes of straight motion — are dissolved one by one from Galileo’s hypothesis.)
[Header: BOOK IX. SECTION IV.]
…[the same stone] — lest it fall down from the vault — it suspends by the sole love with which it desires to consort with its whole, etc. All which things are contrary to reason and experience. Therefore the motion of the earth is not to be admitted.
[Margin: Response.]
It is responded by denying the Major as to the notion of violence in the apparent straight motion; for this too is natural — though secondarily — because it befits a body [that is] out of order and tending toward its place, whereas the circular [motion] befits a body already set in its place. But as to a rock suspended outside the earth’s center, in a terrestrial vault above the air spread around the earth’s center (such that no other terrestrial body were at the center), the Major holds, according to what was said about the terminus toward which of the motion of heavy bodies, in argument 4 of chapter 20, no. 12; for the rock could not be torn from its whole except violently, since at the center there would be no [physical] account of the whole. But what the Copernicans try to answer has been said in the same place.
[Sub-head:] To the many Interrogations and little Questions of Scheiner concerning the principle of this motion, satisfaction is made on this occasion from the hypothesis of the Copernicans, especially of Galileo.
[Margin: 1st Question.]
[VI.] This circular motion of heavy and light bodies — from what principle is it? internal or external? If from an external one: does God excite it by a continual miracle? or is it an Angel? or the Air? — and this [the air] indeed many assign. But against [it] it is, etc.
[Margin: Response.]
It is responded that it is from an internal [principle], and much less from the Air — since the Air itself too is carried in a gyre together with the globe of Earth and Water.
[Margin: 2nd Question.]
If the supreme part of the Air is not moved with the Earth’s diurnal motion, but is exempt from it, how then would heavy bodies let go through it be carried round in a circle?
[Margin: Response.]
It is responded, first, that this experiment has not yet been made by anyone — whether heavy bodies let go through the supreme region of the air would be moved in the same way as [those] let go through our [lower] air. Secondly, that heavy bodies are not carried in a gyre from without, but by an intrinsic force of following and imitating the motion of their primary globe.
[Margin: 3rd Question.]
If this circular motion is from an internal Principle, this principle is either an accident or a substance. If the first — of what kind is it? For no locomotive quality [for moving] in a circle has hitherto seemed to be recognized. And even if there were [such], how would it be found in things so contrary? In fire as in water? in air as in earth? in living things as in those lacking a soul?
[Margin: Response.]
It is responded that it is an accident, whose effect we cannot recognize through the senses, because we too are moved together with the Earth; but if we were outside the elementary world, we would see this circular motion. Furthermore, to things diverse and contrary, contrary motions do not belong — that is, to light bodies the downward motion does not belong, nor to heavy bodies the upward — just as neither do those [motions] which depend on a soul [belong] to inanimate things. But those motions which are not contrary but common — of which kind is circular motion (which, even on Aristotle’s testimony, can be mixed with the straight) — can belong to diverse and contrary natures; just as the downward motion belongs to innumerable bodies diverse in species.
[Margin: 4th Question.]
If the Earth stood still by the will of God, would the rest [of the bodies] be rotated, or not? If [they would], it is false that [a body] gyrates by nature; if [they would not], the previous questions return. And surely it would be wondrous that the Seagull could not — even willing — hover over the little fish, the Lark over its little nest, the Crow over the snail and the rock.
[Margin: Response.]
It is responded, first, that it is uncertain what God would will these [bodies] to be, if he perpetrated that miracle. Secondly, that if no other miracle were made than in stopping the earth, the rest of the bodies cognate to the earth — but accustomed to be driven by a blind impetus, and accordingly neither understanding nor feeling the privation of motion made in the Earth — would proceed in their motions; and that those animals could not then hover over the said bodies, because these [bodies] are supposed to be inhibited [stopped] with the Earth, while [the animals] themselves would be carried in a gyre by natural necessity, not impeded by God. Thirdly, just as, if the Earth (which Scheiner posits to stand still) — while the Seagull, the Lark, etc. hovered over the said bodies and were moved by no proper motion — were meanwhile, together with the adhering bodies, at once snatched elsewhere by a divine miracle, they [the birds] could not at all hover over them; so neither could they [hover], on Copernicus’s hypothesis, if the Earth be stopped by a miracle and this miracle be not made in them, but their natural principle be permitted to move them in a gyre.
[Margin: 5th Question.]
How does it come about that those things, so various, are moved only from West to East, parallel to the Equator? so that they are always moved and never rest?
[Margin: Response.]
It is responded that these [things] come about exactly as, on the opposite and Ptolemaic hypothesis, the Fixed stars are moved from East to West, describing lines parallel to the Equator as regards the diurnal motion — and that without ceasing.
[Margin: 6th Question. Response.]
Why are the higher [bodies moved] more swiftly, the lower more slowly? It is responded: because, by the common law of circles described from the same center, if all revolve in the same time, the parts more remote from the center are carried through greater circles, and so are swifter, since in the same time they accomplish a greater space. But this seems to assign a Geometric reason rather than a physical one.
[Margin: 7th Question. Response.]
Why are those nearer the Equinoctial carried in a greater circle, those more remote in a smaller? It is responded that this comes about in the [same] manner in which, on the contrary hypothesis, the Stars nearer the Equinoctial are moved in greater circles than the more remote; and they would do this even if they were moved by themselves, and not [in subjection] to the motion of the eighth sphere, so as to preserve the laws and proportion of the diurnal revolution. But the stars have this from an Intelligence, or from their own nature (a natural motion being supposed, by which they transfer themselves to such a position of the sphere); whereas heavy bodies do not have this from their own nature, so as to require to be now above one parallel, now above another. And therefore the Response does not satisfy quite equally.
[Margin: 8th Question.]
Why would the same ball, under the Equinoctial, be turned wholly about the earth’s center in a maximum circuit, with incredible speed; but under the pole [be turned] about its own center, with no gyration, with supreme slowness? For in the same time it would accomplish far less space in its descent over the poles along a straight line, than if it descended in the plane of the Equator.
[Margin: Response.]
Galileo responds (Italian page 236, Latin 178) that this comes about in imitation of the Fixed [stars], which would do the same if the diurnal motion were attributed to them, and one star placed at the Equator were compared with a star fixed at the pole of the Equator. So, then, the ball — because it imitates the motion of its primary globe — if placed at the Equator, is carried in a gyre like the terrestrial Equator; if over the poles, it is not carried in a gyre, just as neither [is] the pole, which is supposed immobile as regards the diurnal motion.
[Margin: 9th Question.]
Why does the same thing — a leaden ball, for example — if it once went around the earth by a described maximum circle at the Equator, not migrate around [in] that same maximum circle wherever it is placed, but, transferred outside the Equinoctial, is driven in smaller circles?
[Margin: Response.]
It is responded that the same happens to this [ball], as regards the diurnal gyration, as would happen — indeed, according to Ptolemy, already happens — to the fixed stars, which once moved at the Equator, afterward in parallels to the Equator. But see the response to Question 7.
[Margin: 10th Question.]
If the circular carrying is natural to heavy and light bodies, what is that [carrying] which takes place along a straight line? For if [the straight is] natural, how is also the circular motion natural, since it differs in species from the straight? If [the straight is] violent, how does it come about that a fiery missile flying upward raises its sparkling head from the earth, but is not revolved in a circle — since the upward motion is lesser and violent, [while] the circular is more vehement and natural? Why do falling thunderbolts not draw their tail according to the rule of the circular motion (natural to them), but rather according to the lead of the violent? — so that they extend it upward.
[Margin: Response.]
Galileo responds that it has been said six hundred times that this circular motion is natural and per se primarily intended, but the straight — or rather [the motion] mixed of straight and circular — [is] natural on the supposition that the bodies are out of order and outside their place. Furthermore, that we do not notice a circular motion of this kind, because it is common to us.
[Margin: 11th Question.]
Why does the center of a fallen sphere, under the Equator, describe a spiral in its plane? under the other parallels, a spiral on a cone? under the pole, a straight line congruent to the axis — [the ball] itself, with its extreme point, running down a gyral line designated on a cylindrical surface?
[Margin: Response.]
Galileo responds that this comes about because heavy bodies descend along lines drawn from the center to the circumference of the sphere; but lines of this kind, the earth being moved by the force of the diurnal whirling, at the Equator designate a circle; while those which terminate in the parallels describe conic surfaces; and the axis…
[…continues on p. 439 (PDF 474) with the catchword “autem” (axis autem ipse nihil describit) — “…but the axis itself describes nothing, but remains in itself,” completing the answer; whereupon Galileo concludes that nothing in Scheiner’s little questions weighs against the Earth’s motion, and Chapter XXIV ends.]
(printed p. 439 — Chapter XXIV closes: the eleventh Question’s answer finishes and Galileo concludes that nothing in Scheiner’s interrogations weighs against the Earth’s motion. Then Chapter XXV opens, proposing eleven arguments against the annual motion alone, drawn from the place due to the Earth in the World: after a roster of authorities and Buchanan’s verse on the Pythagorean central Fire, Riccioli begins transcribing and explaining Aristotle’s De Caelo II.13 (texts 72–75) against the Pythagoreans.)
[Header: DE SYSTEMATE TERRÆ MOTÆ — 439]
…but the axis itself describes nothing, but remains in itself. Galileo therefore concludes (Latin page 179, Italian 237) that from all these little interrogations of Scheiner he can gather nothing which has any weight against the motion of the Earth — and rightly; for Scheiner, had he looked more deeply into the Copernican hypothesis, could have answered himself, and accordingly abstained from many (if not from all) little questions of this kind.