Astronomia Nova, is arguably Kepler’s most famous work. Analyzing Tycho’s observations of Mars, Kepler breaks with millennia of tradition. Encouraged by Nicholas of Cusa’s style of mathematical Platonism assuming perfect heavenly spheres to be absurd, and under the weight of Tycho’s observations, Kepler concludes that planetary orbits are not perfect circles but rather the next best thing: ellipses. This has become to be known as Kepler’s First Law of Planetary Motion. Astronomia Nova also contains Kepler’s Second Law specifying the rate of orbital motion. The book was published in 1609, just months before Galileo’s report on his first astronomical observations with a telescope, Sidereus Nuncius.
Look carefully at the title page of Kepler’s groundbreaking 1609 work:
Notice that the entire text of the title page is a single sentence. It goes,
Astronomia Nova Αἰτιολόγητος seu Physica Coelestis, tradita commentariis de motibus stellae Martis ex observationibus G[entilis] V[iri] Tychonis Brahe: Jussu & sumptibus Rudolphi II. Romanorum Imperatoris &c: Plurimum annorum pertinaci studio elaborata Pragae, a S[u]ae C[aesare]ae M[aiesta]tis S[anct]ae Mathematico Joanne Keplero, cum eiusdem C[aesare]ae M[aiesta]tis privilegio speciali Anno aerae Dionysianae MDCIX.
The one and the same Wikipedia entry provides two translations of the first part of into English: (1) “New Astronomy, reasoned from Causes, or Celestial Physics, Treated by Means of Commentaries on the Motions of the Star Mars, from the Observations of the noble Tycho Brahe,” and (2) “New Astronomy, Based upon Causes, or Celestial Physics, Treated by Means of Commentaries on the Motions of the Star Mars, from the Observations of Tycho Brahe, Gent.” The latter is probably due to William H. Donahue’s excellent 2015 English edition of the work.
Here is my translation:
New Aetiological Astronomy or Celestial Physics treated by means of commentaries on the motions of the star Mars, from the observations of the noble Tycho Brahe, by decree and with the support of Rudolph II, Emperor of the Romans, &c., wrought in Prague in many years of pertinacious effort by Johannes Kepler, Mathematician of His Holy Imperial Majesty, with the same Imperial Majesty’s special privilege, in the year 1609 of the Dionysian Era.
And here is Donahue’s:
New Astronomy, Based upon Causes, or Celestial Physics, Treated by Means of Commentaries on the Motions of the Star Mars, from the Observations of Tycho Brahe, Gent., by order and munificence of Rudolph II, Emperor of the Romans, &c., worked out in Prague in a tenacious study lasting many years, by His Holy Imperial Majesty’s Mathematician Johannes Kepler, with the same Imperial Majesty’s special privilege, in the year of the Dionysian Era MDCIX.
As an exercise, I have only allowed myself to read Donahue’s translation after I translated the page myself. Unsurprisingly, the two versions are very close. The obvious problem is the Greek word Αἰτιολόγητος. Leaving it for the last, let us first examine a few miscellaneous items.
Regarding the initials “G. V.” introducing Tycho’s name, I conjecture that they stand for Gentilis Vir (or rather, Gentilis Viri, as the context demands a genitive case). It is a ridiculously ambiguous expression. In medieval Latin it was often rather unflattering, meaning “a pagan (man)” or even “an uncouth man” but Kepler obviously uses it as an honorific, akin to the original meaning of the English title “gentleman” (a nobleman, a member of the gentry, a landowner or a man of independent means). I opt for “noble” because Tycho was heir to several of Denmark’s most influential noble families. Calling him a “gentleman” would be beneath his elevated pedigree.
I love Donahue’s translation of sumptibus as “by munificence”. My translation, “with the support”, is pedestrian in comparison.
As for studium pertinax (the text uses the ablative case, studio pertinaci), I think stay closer to the Latin meanings and connotations. The primary meaning of the word studium comes from the verb studeo, rendered by Charlton T. Lewis’s & Charles Short’s Latin Dictionary as, “to speed, haste, to be eager or zealous, to take pains about, be diligent in, anxious about, busy one’s self with, strive after, to apply one’s self to or pursue some course of action, etc.; to desire, wish, etc.” And while pertinax and tenax and their English versions “pertinacious” and “tenacious” are basically synonyms, the former carries more than a hint of stubbornness. This part of the title sounds a little out of place. Its presence, however, is justified by the contents of the book. Kepler, unlike Newton and many others, does not restrict himself to the data, the analysis, the discussion and the conclusions, but rather, he recounts a tale of his labors and of his discovery in minute detail (although the narrative is probably more pedagogical than biographical as cogently argued by James R. Voelkel, The Composition of Kepler’s Astronomia Nova, Princeton 2001).
I have misgivings about translating Kepler’s most cherished title, Mathematicus Imparialis, as “Imperial Mathematician.” Perhaps we all err in opting for the easy translation here. Truth be told, the word “mathematician” in current usage is not even an approximate equivalent of the 17th century mathematicus. In Kepler’s day everybody knew that the task and responsibility of the courtly “mathematician” was to provide astrological advice to the monarch. Indeed, such were Kepler’s official duties at Rudolph II’s court. The correct and honest functional translation of Kepler’s title ought to be “Imperial Astrologer.”
The “Dionysian Era” is the Christian Era derived (somewhat inaccurately) from historical references by the Abbot Dionysius Exiguus, originally from Scythia Minor (Black Sea coast south of the Danube delta), who was a scholarly member of the Roman Curia throughout most of the first half of the 6th century. The years of the Dionysian Era are traditionally designated as “Anno Domini”. Kepler was well aware of the inaccuracy of the good Abbot’s calculations, and by 1614 he calculated, using his own laws of planetary motion, that that our Lord Jesus Christ was born in the year 7 before the Dionysian Era (De Vero Anno quo Aeternus Dei Filius Humanam Naturam in Utero Benedictae Virginis Mariae Assumsit, Frankfort, 1614). It would sound silly to say that Christ was born in 7 Before Christ (B.C.)…
Let us turn to the neglected Greek word αἰτιολόγητος. Liddell, Scott & Jones have no entry for Kepler’s αἰτιολόγητος. They have, however, entries for two opposites, δυσαιτιολόγητος and ἀναιτιολόγητος, as well as 20 other entries ending in -λογητος. Here are a few:
δῠσ-αιτῐολόγητος, ον, hard to account for, Ph.2.644, Gal.13.605.
ἀναιτιολόγητος, ον, for which no cause can be assigned, Dsc. Ther. Praef., Alex. Aphr., Ptol. Tetr. 111.
ἀφῠσιολόγ-ητος, ον, not to be explained by science, Epicur.Fr.141, 200. II without knowledge of natural laws, in Adv. -τως, φαντάζεσθαι prob. in M.Ant.10.9.
ἀναστρολόγητος, ον, ignorant of astronomy, Str.2.1.19.
εὐλογ-ητός, ή, όν, blessed, ib. Ge. 9.26,al., Ph.1.453, Ev.Luc. 1.68, Ep.Rom.1.25, etc.
ἀναπο-λόγητος , ον, inexcusable, Plb.12.21.10, Ep.Rom.1.20, 2.1; undefended, “τινὰ ἐάσειν” D.Chr.2.39, cf. Eun.VSp.489 B.; without making a defence, D.H.7.46.
εὐαπο-λόγητος , ον, easy to excuse, Str.10.3.1, Plu.Agis 17, Hierocl.in CA19p.461M. (Liddell-Scott-Jones 1940)
The core of Kepler’s word is the noun αἰτία, here obviously in the sense of a cause:
αἰτί-α, ἡ, II cause, διʼ ἣν αἰτίην ἐπολέμησαν Hdt.Prooem., cf. Democr.83, Pl.Ti.68e, Phd.97a sq., etc.; on the four causes of Arist. v. Ph. 194b16, Metaph. 983a26: —αἰ. τοῦ γενέσθαι or γεγονέναι Pl.Phd.97a; τοῦ μεγίστου ἀγαθοῦ τῇ πόλει αἰτία ἡ κοινωνία Id.R.464b:—dat. αἰτίᾳ for the sake of, κοινοῦ τινος ἀγαθοῦ Th.4.87, cf. D.H.8.29:—αἴτιον (cf. αἴτιος II.2) is used like αἰτία in the sense of cause, not in that of accusation. (Liddell-Scott-Jones 1940.)
Whence we have:
αἰτιο-λογία, ἡ, giving the cause of a thing, Democr.118, Aenesid. ap. S.E.P. 1.181, Phld.D. 1.10, A.D.Conj. 231.16; ἡ <περὶ> τῶν μετεώρων αἰ. Epicur. Ep.2p.42U. (Liddell-Scott-Jones 1940.)
And:
αἰτιολογέω inquire into causes, reason, account for, ὑπὲρ τῶν μετεώρων Epicur. Ep. 1 p. 31U., cf. Diocl. Fr. 112, Plot. 6.7.3, Plu. 2.689b; τὸ ζητούμενον Aenesid. ap. S.E. P. 1.181, cf. Demetr.Lac. 1012.68 ; — Pass., ἐκ τοῦ συνδέσμου ᾐτιολογημένον ἐστίν the conjunction indicates that the cause resides in…, ADysc. Conj. 235.9. (Liddell-Scott-Jones 1940.)
αἰτιολογέω auch med., den Grund aufsuchen und angeben, τί, für etwas, Plut. Symp. 6.3.1. (Pape 1880)
αἰτιολογέω-ῶ, rechercher ou expliquer les causes, PLUT. M. 689 b ; GAL. 2, 365 ; SEXT. 40, 18 Bkk. etc. Moy. m. sign. DYSC. Conj. 507. Étym. : αἰτία, λόγος. (Bailly 2020)
It is from this verb that Kepler’s αἰτιολόγητος derives. Generally speaking, verbal adjectives in -τος (m. & f.), -τον (n.) and with a recessive accent, are similar to the English verbal adjectives of ability ending in -able but, unlike the English ones, the Greek ones, in most cases, bear a negative connotation (εὐαπολόγητος , ον is an exception). The verbal adjectives in -τός (m.), -τή (f.), -τόν (n.) tend to be what some grammarians call perfective quasiparticiples, e.g., εὐλογητός, ή, όν, roughly equivalent to English -ed participles. Considering how Kepler uses αἰτιολόγητος in the sentence, it is clearly the feminine form, which means that we are in the realm of verbal adjectives in -τος (m. & f.), -τον (n.). This does not indicate the -able meaning (“aetiologizable”) here. The word denotes a positive concept, i.e., it is a quasiparticiple (“aetiologized”).
[Why does Kepler not say ἀστρονομία αἰτιολογητή? A glance at LSJ shows that, as a general rule, all compound verbal adjectives derived using -το-, regardless of meaning (see above), are adjectives of two endings. Exceptions like εὐλογητός, ή, όν, blessed, while technically compounds, may have been perceived as simple concepts.]
We have thus laboriously established that Kepler’s aitiologētos is without a doubt a verbal adjective in -τος (m. & f.), -τον (n.), with the value of a perfective quasiparticiple, and that Kepler did not err in using this form.
What would be a good English translation? Here is the OED entry for aitiology:
aetiology|etiology, n.Etymology: < classical Latin aetiologia inquiry into, or explanation of, causes, in post-classical Latin also in medical context (1602 or earlier) < ancient Greek αἰτιολογία < αἰτία responsibility, guilt, blame, accusation, cause, reason ( < αἴτιος culpable, responsible < an unattested noun (compare ἔξαιτος choice, excellent) < the stem of αἴνυσθαι to take hold of, seize ( < the same Indo-European base as Tocharian B ai- to give) + -τος , suffix forming adjectives) + -λογία -LOGY comb. form. Compare Middle French aitiologie, French étiologie, †aetiologie (1550 in an apparently isolated attestation, and subsequently from 1694, in medical context; 1611 in philosophical context), Spanish etiología (1580), Italian eziologia (1631 as †etiologia; earliest in medical context).
There are three meaning, which I shall summarize (the full OED entry is 3 pages long). (1) Substantive forms of: assign a cause, provide a reason. Cause or reason assigned. May also be negative: assign responsibility, blame (“his story… has a distinct savour of aetiology” 1893). (2) Study of causation, etc. “Now rare.” (3) Medicine. Medical English makes frequent use of this word, spelled “etiology” or, less commonly but more correctly, “aetiology”.
Kepler felt the need to qualify his “new astronomy” with a new adjective (I am relying on LSJ regarding the word’s absence in the classical corpus) in order to separate it from previous approaches. I ventured to translate αἰτιολόγητος as “aetiological” although I am aware that this is an adjective derived directly from the noun, rather than a verbal adjective. The exact equivalent of “aetiological” would be αἰτιολόγικη (feminine). The verbal adjective is more dynamic, emphasizing action.
Difficulties with translation notwithstanding, I believe that the attribute ought not to be omitted from the short title. A simple and recognizable adjective is called for.
In my search, I turned to German for inspiration. Max Caspar (the editor of Kepler’s Gesammelte Werke in 22 volumes) published an excellent German edition of the work in 1929 under the title, Astronomia Nova: Neue, ursächlich begründete Astronomie. He used a past participle qualified by an adverb (ursächlich, like most German adjectives, is also an adverb). Unfortunately, even Caspar failed to find a one-word equivalent for αἰτιολόγητος. Most disappointing. I had hoped that German was the language allowing one to coin at least three apt German compounds as equivalents for any conceivable Greek compound…
When one translates αἰτιολόγητος by several words, Kepler’s intention inevitably dissipates. The phrase becomes cumbersome, and the attribute is invariably omitted from the short title. If the title is abbreviated as Astronomia Nova, a claim to this astronomy’s novelty is expressed but not specified: What makes it new? It is Kepler’s aetiological approach. That is why I prefer, “New Aetiological Astronomy.”
The word “physics” calls for a footnote. In Kepler’s time physica was a Greek-based synonym for the Latin (or rather, somewhat less Greek) term philosophia naturalis (natural philosophy). Indeed, the major text read in a typical natural-philosophy course was Aristotle’s Physica. This has very little to do with our, post-Newtonian understanding of the term and the discipline. The most important difference was that the predominant view in Kepler’s time was that mathematical models of planetary motion were below the lofty realm of natural philosophy. The latter’s task was to provide explanations, based on causes (as well as, and ultimately, based on appeals to the “nature” of things). Mathematical models were mere descriptions, offering no deeper understanding of the phenomena. Thus Kepler’s second title Physica Coelestis carries essentially the same meaning as the first, fully Greek one Astronomia Αἰτιολόγητος.
[Physica Coelestis would be (τὰ) οὐράνια φυσικά, or ἡ φυσική ἡ οὐράνια, or ἡ οὐράνια φυσική. Astronomia Nova Αἰτιολόγητος would be ἡ νέα ἀστρονομία ἡ αἰτιολόγητος.]
Kepler’s emphasis on explaining planetary motion by “physical causes” is clear and explicit from his Introduction. This is not the occasion, however, to ponder the success and shortcomings of this undertaking. The obvious and declared goal was to identify physical causes. There was another task, underlying the issue, viz., to determine what type of factors constituted “physical causes.” To us, with the benefit of 400 years of hindsight, it may seem trivial but Kepler was entering unchartered territory. Indeed, his “true theory of gravity” applies something “like magnetism” but based on bonds of “kindred” (corpora cognata) to the Earth-Moon system and to other “corporeal substances”:
If two stones were set near one another in some place in the world outside the sphere of influence of a third kindred body, these stones, like two magnetic bodies, would come together in an intermediate place, each approaching the other by an interval proportional to the bulk [moles] of the other. If the moon and the earth were not each held back in its own circuit by an animate force or something else equally potent, the earth would ascend towards the moon by one fifty-fourth part of the interval, and the moon would descend towards the earth about fifty-three parts of the interval, and there they would be joined together; provided, that is, that the substance of each is of one and the same density [because the calculation is based on volumes but they ought to be based on moles].
In this work, Kepler’s “gravity” is limited, effectively, to the Aristotelian sublunary world, but it is already a most inspiring step towards Newton’s gravitational actio in distans, including the linear dependence on what will Newton call massa, but short of the inverse square law. Already in Dioptricē 1611, he extends the concept to Jupiter and its four satellites, which form a celestial family of their own, bound by the same type of ties of kindred as the Earth-Moon pair; the latter is bonded by the bodies’ earthiness, while the Jovian family has its own bond, a “jupiteriness”; and in 1611 none of this has anything to do with the planets orbiting the Sun. Kepler develops his theory further in the Epitome 1618-1621. The Sun is included in Kepler’s concept of gravity here. The notions of kindred are less important and Kepler focuses on quasi-magnetic emanations, decreasing with distance as 1/r or 1/r2.
Although Kepler discovered the Second Law which we, thanks to Newton, see as a consequence of the conservation of angular momentum, Kepler remained unaware of the significance of angular momentum and of its conservation.
The obvious gems in Astronomia Nova Aitiologetos are the two Laws of planetary motion. They belong soundly in the realm of phenomenological descriptions rather than causal explanations. The bulk of the treasure trove, however, is more subtle and less well known. It was Kepler’s aetiological approach that was momentous on the journey towards a full union of the heavenly and the earthly.
| Executive summary |
| Do not omit the Greek attribute from the short title of Kepler’s 1609 work Astronomia Nova Aitiologetos. |
| The least unfaithful English translation of the title is “New Aetiological Astronomy.” |
Acknowledgment.I am most grateful to Fr. Justin Whittington, S.J., for his kind and thoughtful review of my excursions into classical philology.
