The Essential Galileo (33 page)

10.
Galilei 1890–1909, 6: 347.22-352.14; newly translated by Finocchiaro.

11.
Here and in the rest of this selection,
tiny particle
, or simply
particle
, is my translation of Galileo's
particella minima, or corpicello minimo, or simply minimo
.

12.
Cf. the discussion in section 44 of
The Assayer
: Galilei 1890–1909, 6: 336–39; Drake and O'Malley 1960, 297–300.

CHAPTER 8
¹

From
Dialogue on the
Two Chief World Systems
(1632)
²

[§ 8.1 Preface:To the Discerning Reader]
³

[29] Some years ago there was published in Rome a salutary edict
⁴
which, to prevent the dangerous scandals of the present age, imposed opportune silence upon the Pythagorean opinion of the earth's motion. There were some who rashly asserted that that decree was the offspring of extremely ill-informed passion and not of judicious examination; one also heard complaints that consultants who are totally ignorant of astronomical observations should not cut the wings of speculative intellects by means of an immediate prohibition. Upon noticing the audacity of such complaints, my zeal could not remain silent. Being fully informed about that most prudent decision, I thought it appropriate to appear publicly on the world scene as a sincere witness of the truth. For at that time I had been present in Rome; I had had not only audiences but also endorsements by the most eminent prelates of that court; nor did the publication of that decree follow without some prior knowledge on my part. Thus it is my intention in the present work to show to foreign nations that we in Italy, and especially in Rome, know as much about this subject as transalpine diligence can have ever imagined. Furthermore, by collecting together all my own speculations on the Copernican system, I intend to make it known that an awareness of them all preceded the 190 Roman censorship, and that from these parts emerge not only dogmas for the salvation of the soul, but also ingenious discoveries for the delight of the mind.

To this end I have in the discussion taken the Copernican point of view, proceeding in the manner of a pure mathematical hypothesis and striving in every contrived way [30] to present it as superior to the viewpoint of the earth being motionless, though not absolutely but relative to how this is defended by some who claim to be Peripatetics; however, they are Peripatetics only in name since they do not walk around but are satisfied with worshipping shadows, and they do not philosophize with their own judgment but only with the memory of a few ill-understood principles.

Three principal points will be treated. First, I shall attempt to show that all experiments feasible on the earth are insufficient to prove its mobility but can be adapted indifferently to a moving as well as to a motionless earth; and I hope that many observations unknown to antiquity will be disclosed here. Second, I shall examine celestial phenomena, strengthening the Copernican hypothesis as if it should emerge absolutely victorious and adding new speculations; these, however, are advanced for the sake of astronomical convenience and not for the purpose of imposing necessity on nature. Third, I shall propose an ingenious fancy. Many years ago I had occasion to say that the unsolved problem of the tides could receive some light if the earth's motion were granted. Flying from mouth to mouth, this assertion of mine has found charitable people who adopt it as a child of their own intellect. Now, so that no foreigner can ever appear who, strengthened by our own weapons, would blame us for our insufficient attention to such an important phenomenon, I decided to disclose those probable arguments which would render it plausible, given that the earth were in motion. I hope these considerations will show the world that if other nations have navigated more, we have not speculated less, and that to assert the earth's rest and take the contrary solely as a mathematical whim does not derive from ignorance of others' thinking but, among other things, from those reasons provided by piety, religion, acknowledgment of divine omnipotence, and awareness of the weakness of the human mind.

Furthermore, I thought it would be very appropriate to explain these ideas in dialogue form; for it is not restricted to the rigorous observation of mathematical laws, and so it also allows digressions which are sometimes no less interesting than the main topic.

Many years ago in the marvelous city of Venice I had several occasions to engage in conversation with Giovanfrancesco Sagredo, a man of most illustrious family and of sharpest mind. From Florence we were visited by [31] Filippo Salviati, whose least glory was purity of blood and magnificence of riches; his sublime intellect fed on no delight more avidly than on refined speculations. I often found myself discussing these subjects with these two men, and with the participation of a Peripatetic philosopher, who seemed to have no greater obstacle to the understanding of the truth than the fame he had acquired in Aristotelian interpretation.

Now, since Venice and Florence have been deprived of those two great lights by their very premature death at the brightest time of their life, I have decided to prolong their existence, as much as my meager abilities allow, by reviving them in these pages of mine and using them as interlocutors in the present controversy. There will also be a place for the good Peripatetic, to whom, because of his excessive fondness of Simplicius'
⁵
commentaries, it seemed right to give the name of his revered author, without mentioning his own. Those two great souls will always be revered in my heart; may they receive with favor this public monument of my undying friendship, and may they assist me, through my memory of their eloquence, to explain to posterity the aforementioned speculations.

These gentlemen had casually engaged in various sporadic discussions, and, as a result, in their minds their thirst for learning had been aroused rather than quenched. Thus they made the wise decision to spend a few days together during which, having put aside every other business, they would attend to reflecting more systematically about God's wonders in heaven and on earth. They met at the palace of the most illustrious Sagredo, and after the proper but short greetings, Salviati began as follows.

[§8.2 Day II: Independent-mindedness and
Aristotle's Authority]
⁶

[132] S
ALV
.    Yesterday's digressions from the direct path of our main discussions were many, and so I do not know whether I can get back and proceed further without your help.

S
AGR.
    I am not surprised that you are in a state of confusion, given that you have your mind full not only of what has been said but also of what remains; but I, who am a mere listener and know only the things I have heard, will perhaps be able to bring the argument back into line by briefly recalling them. As far as I can remember then, the gist of yesterday's discussions was the examination from its foundations of the question of which of the two following opinions is more probable and reasonable: the one holding that the substance of the heavenly bodies is ingenerable, indestructible, unchangeable, inert, in short, exempt from any but changes of place, and that therefore there is a fifth essence
⁷
very different from the familiar one of our elemental, generable, degradable, and changeable bodies; or else the other opinion which, taking this division of parts away from the world, holds that the earth enjoys the same perfections as the other constitutive bodies of the universe, and is in short a movable and moving globe no less than the moon, Jupiter, Venus, or other planets. Lastly we drew many particular parallels between the earth and the moon, concentrating on the latter perhaps because we have greater and more sensible knowledge of it on account of its lesser distance. Having concluded that this second opinion is more likely than the other, I think that the next step is to begin [133] to examine whether the earth must be considered immovable, as most people have so far believed, or else movable, as some ancient philosophers and others more recently have held; and if it is movable, we must ask what its motion may be.

S
ALV
.    I understand already and recognize the direction of our path. However, before beginning to proceed further, I must say something about the last words you uttered—that we concluded that the opinion holding the earth to have the same properties as the heavenly bodies is more likely than the contrary one. For I have not concluded this, just as I am not about to conclude any other controversial proposition; instead I have meant to produce, for one side as well as for the other, those reasons and answers, questions and solutions which others have found so far, together with some that have come to my mind after long reflection, leaving the decision to the judgment of others.
⁸

S
AGR.
    I let myself be carried away by my own feelings and made universal a conclusion that should have been left individual, thinking that others should feel what I felt within myself. Indeed I erred, especially since I do not know the opinion of Simplicio present here.

S
IMP.
    I confess to you that I thought about yesterday's discussions the whole night, and I really find many beautiful, new, and forceful considerations. Nevertheless, I feel drawn much more by the authority of so many great writers, and in particular…
⁹
You shake your head and sneer, Sagredo, as if I were saying a great absurdity.

S
AGR.
    I merely sneer, but believe me that I am about to explode by trying to contain greater laughter; for you reminded me of a beautiful incident that I witnessed many years ago together with some other worthy friends of mine, whom I could still name.

S
ALV
.    It will be good for you to tell us about it, so that perhaps Simplicio does not continue to believe that it was he who moved you to laughter.

S
AGR.
   . I am happy to do that. One day I was at the house of a highly respected physician in Venice; here various people met now and then, some to study, others for curiosity, in order to see anatomical dissections performed by an anatomist who was really no less learned than diligent and experienced. It happened that day that they were looking for the origin and [134] source of the nerves, concerning which there is a famous controversy between Galenist
¹⁰
and Peripatetic physicians. The anatomist showed how the great trunk of nerves started at the brain, passed through the nape of the neck, extended through the spine, and then branched out through the whole body, and how only a single strand as thin as a thread arrived at the heart. As he was doing this he turned to a gentleman, whom he knew was a Peripatetic philosopher and for whose sake he had made the demonstration; the physician asked the philosopher whether he was satisfied and sure that the origin of the nerves is in the brain and not in the heart, and the latter answered after some reflection: “You have made me see this thing so clearly and palpably that one would be forced to admit it as true, if Aristotle's texts were not opposed in saying plainly that the nerves originate in the heart.”

S
IMP.
    Gentlemen, I want you to know that this dispute about the origin of the nerves is not as settled and decided as some believe.

S
AGR.
    Nor will it ever be decided as long as one has similar opponents. At any rate what you say does not diminish at all the absurdity of the answer of the Peripatetic, who against such a sensible experience did not produce other experiences or reasons of Aristotle, but mere authority and the simple ipse dixit.
¹¹

S
IMP.
    Aristotle has acquired such great authority only because of the strength of his arguments and the profundity of his discussions. However, you must understand him, and not only understand him, but also know his books so well that you have a complete picture of them and all his assertions always in mind. For he did not write for the common people, nor did he feel obliged to spin out his syllogisms by the well-known formal method; instead, using an informal procedure, he sometimes placed the proof of a proposition among passages that seem to deal with something else. Thus, you must have that whole picture and be able to combine this passage with that one and connect this text with another very far from it. There is no doubt that whoever has this skill will be able to draw from his books the demonstrations of all knowable things, since they contain everything.

S
AGR.
   . So, my dear Simplicio, you are not bothered by things being scattered here and there, and you think that by collecting [135] and combining various parts you can squeeze their juice. But then, what you and other learned philosophers do with Aristotle's texts, I will do with the verses of Virgil or Ovid, by making patchworks of passages and explaining with them all the affairs of men and secrets of nature. But why even go to Virgil or other poets? I have a booklet much shorter than Aristotle or Ovid in which are contained all the sciences, and with very little study one can form a very complete picture of them: this is the alphabet. There is no doubt that whoever knows how to combine and order this and that vowel with this and that consonant will be able to get from them the truest answers to all questions and the teachings of all sciences and of all arts. In the same way a painter, given various simple colors placed separately on his palette, by combining a little of this with a little of that and that other, is able to draw men, plants, buildings, birds, fishes—in short, all visible objects—without having on his palette either eyes, or feathers, or scales, or leaves, or rocks; on the contrary, it is necessary that none of the things to be drawn nor any part of them be actually among the colors, which can serve to represent everything, for if there were, for example, feathers, they would not serve to depict anything but birds and bunches of feathers.

S
ALV
.    There are still alive some gentlemen who were present when a professor teaching at a famous university, upon hearing descriptions of the telescope which he had not yet seen, said that the invention was taken from Aristotle. Having asked that a book be brought to him, he found a certain passage where Aristotle explains how it happens that from the bottom of a very deep well one can see the stars in heaven during the day,
¹²
and he said to the bystanders: “here is the well, which corresponds to the tube; here are the thick vapors, from which is taken the invention of lenses; and lastly here is the strengthening of vision as the rays pass through the denser and darker transparent medium.”