The Influence of the Geographic Discoveries upon Copernicus

O R G A N O N 9 (1973) A U T E U R S E T P R O B L E M E S

Thomas G oldstein (U.S.A.)

THE INFLUENCE OF THE GEOGRAPHIC DISCOVERIES

UPON COPERNICUS*

The history of geographic thought is rarely considered as an integral

part of the history o f science. We are inclined to think of the geographic

discoveries primarily in term s of a dramatic “adventure story”, an ex ­

plosion of dynamic energies released by the culture of the Renaissance,

and what theoretical achievem ents w e may be ready to concede to that

collective enterprise seem largely unconnected w ith the im m ediately

following burst o f intellectual energies w hich marked the rise of modern

science, th e Scientific Revolution. If this lack of m eaningful connections

between the emergence of th e early m odem universe and the preceding

cultural and practical-scientific m ovem ents should indicate our present

inadequacy in relating the Scientific Revolution to the general historical

context, this basically “unhistorical” approach is highlighted even more

sharply by an unsolved historical problem in the evolution of theoretical

science itself: Historians o f science have long been puzzled by the appa­

rent gap w hich extends betw een the advanced cosmological insights of

fourteenth century thinkers and the actual formulation of the sun-cen­

tered cosmos, almost tw o hundred years later, by Nicholas Copernicus

(or the physical, mathematical and astronomical im plementations of the

heliocentric system through his successors, w hich crystallized after an

even much longer time). Indeed, so m any basic aspects of the modern

universe had been anticipated by fourteenth century cosmologers like

Jean Buridan, Albert of Saxony or Nicole Oresme (or the mathematicians

of Oxford’s Merton College) that one m ust not only wonder w h y it took

these brilliant insights such a long tim e to mature, but also w h y the

flourishing of Renaissance culture should have acted as a major

inter-* This essay is an expanded version of a paper given at the IVth International Conference on the H istory of Cartography, Edinburgh, Septem ber 23, 1971. A m ore exten sive article on the sam e subject is planned for publication in the 1972 issue of T errae Incognitae.

ruption in the continuous growth of cosmological thought. Should w e as­

sume that th e Renaissance “absorbed” the best creative energies w ith

its artistic and literary-esthetic interests, so that they were only able to

“revert” to the great cosmological problems after the Renaissance had

run its course? Such vague, semi-biological assumptions are hardly the

stuff of serious historical scholarship. 1 Besides, the Renaissance no longer

looks to us like an exclusively artistic (or esthetic) culture. Even though

its scientific contributions have not y et been satisfactorily explored, w e

have begun to recognize that it contained important undercurrents of

scientific thought and that in fact even its art — beyond the phenome­

non of Leonardo da Vinci — involved some vital scientific aspects in

anatomy, perspective, optics and, conceivably, in certain more funda­

m ental areas as w e ll.2 For all its fervor of creative passion the tem per

of the Renaissance no longer seems as alien to system atic scientific stud­

ies as it did a hundred years ago. Why should its flowering have in­

terrupted the steady growth of cosmological thought between the four­

teenth and the middle of the sixteenth century?

The fact (as I shall try to demonstrate) is that it did not. Quite on the

contrary, the most outstanding scientific contribution made w hen Ren­

aissance culture was at its height — the geographic discoveries and the

changed concept of the earth which they produced — provided sixteenth

1 The idea that the R enaissance (or R enaissance hum anism) interrupted the continuity of science is pointedly expressed, e.g., in J. H. Randall, Jr., The M aking of the M odern M ind, Cambridge, Mass., 1940, p. 212, in an otherw ise w e ll-in ­ formed discussion of late M edieval and R enaissance science: “For natural science hum anism was an alm ost unm itigated curse. Had it not centered the energies of the best in tellects on the essentially non-scien tific w isdom of the [...] Romans, these vigorous scien tific interests [of the later Middle Ages] m ight have produced a G alileo long before the seventeenth century.” Also H. Butterfield, The Origins of M odern Science, 1300-1800, N ew York, 1962, p. 21: “Indeed, Galileo could have produced much... that w e find in his juven ile works [on the subject of im p e tu s] if he had lived during the 14th century; and in this field one m ight very w ell ask w hat the world w ith its R enaissance and so forth had been doing in the m eantim e.” T. S. Kuhn, T he Copernican R evolu tion , N ew York, 1957, pp. 127 ff., gives w hat am ounts to an interesting explanation for the “tim e lag” in terms of the influence of R enaissance Neoplatonism on Copernicus (and Kepler). For the spadework of fourteenth cent, science, e.g., H. Butterfield, op. cit., ch. 1: “The H istorical Im portance of a Theory of Im petus”; T. S. Kuhn, op. cit., pp. 115 ff; or E. A. Moody’s highly inform ative essay, L a w s of M otion in M edieval P hysics, in: T ow ard M odern Science, ed. Robert M. Palter, N ew York, 1961, I, pp. 220 ff.

2 I have attem pted a brief sum m ary of recent scholarship on the scien tific aspects of the R enaissance in m y G eography in 15th Cent. Florence, in: M erchants and Scholars, ed. John Parker, M innesota U niversity Press, 1965, pp. 11 f. (with bibl.). See also Joan Gadol, The U nity of th e Renaissance: H um anism , N atural Science and A rt, in: From th e Renaissance to th e C ou nterreform ation , E ssays in Honor o'f G arret M attin gly, ed. Charles H. Carter, N ew York, 1965, pp. 29-55 (re­ printed in T he S cien tific R evolution, ed. V. L. Bullough, N ew York, 1970); J. G a­ dol, Leon B a ttista A lb erti, U niversal Genius of th e Early Renaissance, Chicago U niversity Press, 1969. R enaissance contributions to the Copernican astronomy are discussed briefly in T. S. Kuhn, op. cit., pp. 123 ff. (esp. p. 129, on Domenico Maria de Novara; also L. Sighinolfi, “Dom. Maria N ovara e Nicolö Copernico”, S tu d i e m em orie per la sto ria dell’u n iversitä di Bologna, vol. V, 1920, no. 2, pp. 11-35); and D. Heilm an, “Science in the Renaissance. A S urvey”, Renaissance N ew s (Ren. Society of America), vol. 8, no. 4, W inter 1955.

The Influence of the G eographic D iscoveries upon Copernicus 2 0 1

century cosmologers w ith an important empirical elem ent that had been

m issing in fourteenth century science, w ith the result that early modern

science was able to proceed upon a basis of empirical certainty, w here the

late Middle Ages had been confined to an essentially abstract type of

reasoning, or pure, inspired speculation. The principal evidence for this

presents itself through an analysis of one of the opening chapters of

Copernicus’ R evolutions of the H eavenly Spheres (Book One, ch. 3), in

which Copernicus offers a remarkable interpretation of the new concept

of the earth that had resulted from the recent geographic discoveries,

proceeding to use the “new earth”, in a perfectly concrete and visual

w ay, as a stepping stone for his heliocentric theory, a tangible foundation

for his ascent towards the new cosmos. By interpreting the meaning

of his geographic chapter, in other words, I believe one finds that the

age of the Renaissance, instead of interrupting the continuity of cosmo­

logical thought, had contributed a crucial elem ent to Copernicus’ con­

ceptual process — as w ell as, through his introduction of the new con­

cept of the earth, to the thinking of his successors in the Scientific R ev­

olution. What is more, such an analysis reveals Copernicus’ grasp of

physical problems and his, on the whole, consistent logic in dealing w ith

the non-astronomical premises of his system to a far greater extent than

he is as a rule given credit for by modern h istorians.3

Copernicus’ geographic chapter (including his reference to the recent

discoveries) was brought to the attention of scholars in an article by

Edward Rosen, published in 1943, w ith the suggestion that he had

formed his geographic concepts from Johannes W aldseem ueller’s Cosmo-

graphiae Introductio of 1507. While I do not agree w ith every one of

his arguments in this context, I tend to accept Professor Rosen’s sug­

gestion that W aldseemueller’s Cosm ography, including its map work, was

Copernicus’ principal geographic sou rce.4 On th e other hand, since the

chapter implies that he had formed his ideas by actually studying a map

which represented the new picture of the- earth, he may w ell have de­

rived (or at any rate confirmed) his ideas from the study of any one of

several world maps of the new type that were available by 1512, w hen

he seems to have begun to work on the Revolutions and in all likelihood

wrote the opening chapters. 5 It may be noteworthy that in his

Com-3 See below regarding C opernicus’ intrinsic logic in dealing w ith the non- astronom ical prem ises of his system , as w ell as his physical ideas; also, briefly, for the influence of his concept of the earth on his successors. Copernicus’ a l­ leged failure to cope logically w ith the im plicit physical problems: T. S. Kuhn, op. cit., pp. 148 f.; H. Butterfield, op. cit., ch. 2: “The Conservatism of C opernicus” (esp. pp. 41 ff.).

4 E. Rosen, “Copernicus and the D iscovery of A m erica”, The H isp a n ic -A m e ri­ can H istorical R e view , May 1943, pp. 367-371. The m ost telling of R osen’s argu­ m ents is that Copernicus used the nam e “A m erica” and speaks of it as a “land named after the Captain who discovered it”.

5 On Copernicus beginning his w ork on the R evolu tion s during his stay at H eils- berg castle or at Fromburg, about 1512: A. Arm itage, The W orld of C opernicus (origin­

m entariolus, w ritten as a short summary o f his basic astronomical thesis,

presumably w hile he was setting out on his work on the Revolutions,

Copernicus om itted any references to th e new geographic concepts.

However, even there he clearly operates w ith a concept o f the earth

as rotating “together w ith its circumjacent elem ents” — or “together

w ith its circumjacent waters and encircling atmosphere” — which is

the salient, and decidedly anti-Aristotelian, idea he developed in the

R evolutions from th e n ew geographic evidence. He m ay have reserved

a more explicit geographic elaboration “for m y larger work”, as he did

“for the sake of brevity” w ith respect to his mathematical demonstra­

tions; or else his concept of “our sphere” in the Com m entariolus may

still have lacked the full compactness that it achieved in the R evolu­

tions — a possibility w hich suggests itself as the more plausible one

from his repeated phrasing. 6

A t any rate, it is not suggested here that geographic considerations

ally: Sun S tan d Thou S till, 1947), Mentor Books, N ew York, 1951, pp. 74, 78. The geographic chapter as a w hole is evidently based on th e ideas form ed from visual evidence (cf. the interpretation below). Some argum ents are m oreover directly derived from the study of a map (e>g. that there is a “passage barely 15 stades w id e” betw een the “Egyptian Sea and the Arabian Gulf, w ell-n igh in the m iddle of the great land m ass”; or that “geom etrical argum ent dem ands that the M ain­ land of A m erica on account of its position be diam etrically opposite to the Ganges basin in India” — w hich presupposes that Copernicus visu alized a world map as being transferred upon a globe, presum ably by m easuring th e distances). E xam ples o f w orld maps show ing the N ew World w hich w ere published up to 1512 w ould include th e Cantino world m ap of 1503, or the Contarini w orld m ap (e.g. in the 1506 engraving), or Joannes de Stobniza’s of 1512 (see note 23 below).

6 A. Arm itage, op. cit., p. 74, places the date o f the C om m en tariolus about 1512 “or a little earlier”; E. Rosen, T hree Copernican T reatises, C olum bia U niver­ sity Press, 1939 (2nd ed., D over Publications, N ew York, 1959), pp. 7, 59, points out that no d efinite date can be assigned to the C om m en tariolus, but agrees that it w as w ritten w h ile he w as planning, or beginning work, on the R evolutions. That the C om m en tariolus generally represents an earlier phase in Copernicus’ thinking than th e De revolu tion ibu s is evident from the nature of its heliocentric theory (E. Rosen, op. cit., p. 7). I am inclined to assum e a sim ilar progression for his concept of the earthly sphere because in the C om m en tariolus Copernicus speaks of th e “m otion of the earth and our sphere” (p. 59); or a little later, of “the earth [rotating] togeth er w ith its circu m jacen t w a te rs and encircling atm osphere” (p. 63), i.e. in both instances assum ing an apparent distinction betw een the earth itself and the “sphere” as a w hole, including its pertinent elem ents. Since I find no evidence for R osen’s interpretation (p. 58, n. 4) that Copernicus already in the C om m en tariolus had conceived of w ater as effectiv ely integrated w ith the globe (and therew ith confined to its surface), I b elieve it is reasonable to assum e a conceptual progression from the essen tially m athem atical idea o f th e “sphere” in the C om m en tariolus to the concept o f the globe as a p hysical body, based on geographic evidence, in th e R evolutions. I think this progression (and the final adoption of the concept of the sphere as a three-dim ensional body in the opening chapters of the De revolu tion ibu s) holds true despite Rosen’s very careful argum ent (p. 11 ff.) that Copernicus w as am biguous in his use of the Latin term s cor­ responding to “sphere” as a three-dim ensional body and as a tw o-d im ensional circle or as a purely m athem atical concept (sph aera, orbis, circulus), and that he “avoided taking sides in the controversy over the question w hether the spheres w ere im aginary or real” (p. 11). W hat Rosen is here discussing is the nature of the spheres to w hich the planets (according to th e A ristotelian tradition) are sup­ posed to be attached, not the shape and nature o f th e earthly globe. I b elieve to be able to show below that in th e opening chapters o f the De revolu tion ibu s Copernicus introduced th e concept of the earth as a p hysical body, including w ater, and proceeded to operate w ith this concept in his subsequent arguments. (The tex t of th e C om m en tariolus, in R osen’s E nglish translation, is printed in

The Influence of the G eographic D iscoveries upon C opernicus 203

w ere in any sense a primary factor in causing Copernicus to revise the

geocentric system . His m otivations were first of all mathematical, as he

him self stated clearly in the introduction of th e R evolutions (though

even there his phrasing reflects rather definite Renaissance influences, in

this instance of an esthetic order).7 N evertheless, the role of the new

picture of the earth in Copernicus’ thinking seem s so significant, pre­

cisely because it permitted him to visualize his rotating earth in concrete

physical terms, rather than m erely as a theoretical mathematical h y ­

pothesis which he tried to substantiate through astronomical evidence:

U ntil the earth could be conceived as a “solid” sphere, its rotation would

have had to be imagined in the physically prohibitive term s of the

Aristotelian cosmology, in which the various elem ents occupy their own

separate and by definition stationary “spheres” — so that Copernicus’

innovation would in essence have come down to a mere matter o f opti­

cal relativity (i.e. the inner core of A ristotle’s cosmos rotating around

itself, as w ell as the sun, instead of the universe rotating around that

inner core). This — as w ell as any other conceivable alternative —

would have raised virtually insuperable difficulties w ithin the accepted

system of Aristotelian physics, reducing th e Copernican theory to little

more than a physically unsubstantiated mathem atical abstraction, w hich

is exactly of w hat he is often accused by modern historians. 8 Y et the

new geographic concepts enabled him in fact to think of the earth in the

7 In his Preface to the R evolutions, dedicating the work to Pape P aul III, Copernicus blam es the various geocentric exp lan ations for their lack of a uniform underlying principle and goes on: “With [these m athem aticians] it is as though an artist w ere to gather the hands, feet, head and other m em b ers'for his im ages from diverse m odels, each part excellen tly drawn, but not related to a sin gle body, and sin ce they in no w ay m atch each other, the result w ould be m onster rather than m an” (quoted from the Engl, translation in T. S. Kuhn, op. cit., p. 139). For K uhn’s discussion of R enaissance-N eoplatonic elem ents in the De re volu tion ibu s, see note 1 above. A perceptive discussion of Pythagorean elem en ts in Copernicus thought, in relation to its m usical im plications and affin ities, w as given in a paper by W. Voisé, N icolas Copernic, H istoire d’une d écou verte, at the X H Ith International Congress for the H istory of S cience in M oscow, 1971.

8 See note 3 above for modern criticism of C opernicus’ alleged failu re to cope w ith the im plicit problem s of A ristotelian physics. The prim ary p hysical d ifficulty in his heliocentric theory w ould seem that it violated A ristotle’s law s of m otion by im plicitly separating the earth from the center of th e universe, and by im p ly­ ing a circular m otion for the earth as w ell as its “circum jacent elem en ts”, plus a planetary m otion for both, w h ile the spheres o f th e elem ents in A ristotelian p hysics are generally conceived as stationary, as the sites w here the natural m otion of the elem ents comes to rest (although A ristotle introduces certain q uali­ fications of this idea in the M eteorology); and w h ile natural circular m otion is reserved for the “celestial region” (and therew ith precluded for the “sublunar region”). Copernicus (De rev., I, 8) argues sp ecifically for the p ossib ility of re cti­ linear and circular m otion in evident reference to th e earth and its “associated ” elem ents (or in other words to A ristotle’s “sublunar” region), and even more sp ecifically for the p ossibility of circular m otion as natural to a body’s state of rest (see below , esp. note 26) for a survey of w hat I consider Copernicus’ in trin si­ cally logical attem pt to m odify A ristotelian phisics so as to accom odate his rotat­ ing earth, thereby opening the w ay for th e fundam ental revision of A ristotle’s p hysical system ).

modern sense of the earthly globe, thereby for all intents and purposes

subverting A ristotle’s physical cosmos and, how ever im plicitly, paving

the w ay for the early modern system of universal physics. 9

In the Aristotelian cosmology the concept of an earthly globe as an

integral physical body had been submerged by his famous hierarchy of

concentric spheres, w hich not only divided the globe into the separate

“spheres” of the elem ent earth and water but, by the same token, held

the earth so firm ly tied to the center of the cosmos that any idea of the

globe’s moving across the universe as a planet would have been effec­

tively precluded. In w hat was probably the m ost succinct formulation of

his cosmic vision Aristotle, in Book IV, ch. 5 of the Physics, had stated:

“The earth rests inside the water, the w ater inside the air, [the air again]

inside the ether, and the ether inside the sky, but the sky is no longer

[contained] inside anything else.” 10 Even though he had of course con­

siderably expanded (and to some extent modified) this classically simple

vision, especially in the M eteorology and the De coelo, one m ight consid­

er th is almost poetic statem ent as an apt summary of the cosmological

system he was to bequeath to the next tw o thousand odd y e a r s.11 And

it was in essence of this vision w ith which a long line of M edieval com­

mentators was to w restle and w hich confronted Copernicus, as he set out

to revise the geocentric cosmology.

<J See notes 25, 26 below. T. S. Kuhn, op. cit., p. 146, already observed that Copernicus in his geographic chapter w ished to dem onstrate that the globe is m ade up of solid m atter and that w ater is part of the earthly sphere. Y et in m aking this point rather casually, Kuhn om itted an exp licit interpretation of the geographic content of the chapter and failed to recognize its significance for Coper­ n icu s’ physical thought (accusing him in sequence of his “con servative” adherence to A ristotelian law s, p. 148). In the sam e w ay — i.e, by interpreting the basic m eaning of thg chapter only by a casual rem ark — Kuhn fails to place the chapter in its proper historical context, i.e. as a conscious contribution to the long-standing debate about the structure of the earth (see b elow and notes 17, 18).

10 “Ether” ( o u & f l p ) is som etim es used for the fiery elem ent already by Ho­ mer; cf. K irk-R aven, The P resocratic Philosophers, Cambridge U niversity Press, 1971, p. 10. A ristotle offers a sim ilarly terse form ulation in the De coelo, II. 4 (Loeb C lassical Library, Cambridge, Mass., 1939, p. 161; translated by W. K. C. G uth­ rie): “One m ight also be brought to this b elief [i.e. that the heavens are spheri­ cal] by the consideration of the bodies situated around the center; for if w a ter is found around th e earth, air around th e w a ter and fire around the air, the upper bodies w ill follow the sam e arrangement... B ut th e surface of the w a ter is spherical.”

11 A ristotle’s general doctrine of the four elem ents is in De coelo, Books III-IV; also: De generatione e t corruptione, Book II. His M eteorology (in dis­ cussing origins and transform ations of physical phenomena) contains a number of rather am azing m odifications, e.g.: “We call air the part w hich im m ediately surrounds the earth” (Met., I, 3; Loeb Class. Library, 1952, p. 21; transl. by H. D. P. Lee); or, w hen speaking o f the river Ocean of the ancients as a “river w ith a circular course, w hich rises and falls and is composed of a m ixture of w ater and air” (Met., I, 9; p. 71). The editor’s “Introduction” (pp. X X III ff.), dis­ cusses the place of the M eteorology in the corpus of A ristotle’s w ritings and suggests it m ay h ave been a late work. M edieval com mentators, in discussing the structure of the earth, often liked to refer to the M eteorology, and seem in fact to ow e m any of their m odifications of the unqualified theory, as presented in the De coelo, to that work (see, e.g., note 18 below). But the influence of the resp. A ristotelian w orks on the M edieval debate m ight need closer investigation.

The Influence of th e G eographic D iscoveries upon Copernicus 205

There are several significant implications to this cosmic vision w hich

are relevant in this context — as th ey m ust indeed have been relevant

for Copernicus’ thought: First of all, th e Aristotelian system w as by no

means an arbitrary one. Rather, its order was based upon ostensible

common sense. Out of the various features w hich he had taken over

from his Greek (or earlier ancient) predecessors, Aristotle had construc­

ted a seem ingly rational system that agreed com pletely w ith the naive,

everyday observation of the surrounding universe. To such naive obser­

vation (confirmed by the geographic concepts that prevailed till th e age

of discoveries) the earth appeared in fact as synonym ous w ith the “ha­

bitable earth” — th e known, three-continental land mass, or oikoum ene

— w hile the domain of water, or the “Ocean sea”, seemed to be as much

of an “outer sphere”, part of the surrounding cosmos, as it m ay easily

appear to: us w hen w e are looking out at the ocean from a deserted

beach. A ristotle’s cosmos in this sense m ight be seen as a formidable

system atization (and rationalization) of all the anim ist view s that had

reigned throughout the ancient world, whose common meaning has been

that man confronted the natural universe as something outside him self,

or at any rate outside his immediate habitat.

Under this viewpoint, the sequence of the elem ents seemed to be

invariably determined by A ristotle’s law s of natural motion, w hich were

in turn founded in ostensible common sense: “Earth” had to be at the

center of the cosmic structure, because earth tended to sink to the

ground; w ater (as everyday observation suggested) tended to collect

above earth; air rises up and m ust therefore collect in a sphere above

water; fire tends to shoot up towards the sky, and therefore collects in

a yet more distant sp h ere.12 No m atter w hat logical or empirical prob­

lem s thfs order m ight raise (of which Aristotle w as of course aware

and w hich he discussed w ith his usual perspicuity), the order itself w as

firm ly preordained, so that a person looking out from a deserted beach

seem ed in fact to be looking at a sequence of “shells” that surrounded

him concentrically, before he could see the s k y .13 The orbits of the stars

around the earth (which again seem ed a m atter of comm on-sense obser­

vation) w ere in fact an extension of this elem entary concentric order, so

that the geocentric astronomy was in turn inextricably tied to a basic

framework o f elem entary physics, as part of a universal physical cosmol­

ogy. Anyone w ishing to re-think the geocentric system , transposing it

into heliocentric terms, would first have to cope w ith these fundam ental

12 See, e.g., De gen eration e et corruptione, Book II, 3, (330b): “The sim ple bodies, then, being four in number, make up tw o pairs belonging to two regions; for Fire and Air form the body w hich is carried along towards the ‘lim it’, w h ile Earth and Water form the body w hich is carried along tow ards the center” (from A risto tle, ed. Abraham Edel, Laurel Great L ives and Thought Series, N ew York, 1967, p. 264).

18 The problem o f how both earth and w ater could be conceived in term s of these “spheres” is discussed below , in connection w ith the M edieval debate.

law s o f Aristotelian physics and w ith th e earth- or, rather, “land”-cente-

red outlook upon the universe which they implied. However, even be­

fore he m ight tackle that problem, he could conceivably do something

else: He could “detach” the innermost core — primarily earth and water

— from its context w ith the cosmic structure and integrate it into one

common solid body, thereby placing both the concentric order of the

elem ents and the physical law s which determined that order in doubt —

or, in other words, unhinging the w hole system , including the concen­

tric orbits of the stars, from its very center. — Which is exactly what

Copernicus did. If modern historians like to charge him w ith an illogical

approach (because the revision of A ristotle’s law s of motion should have

preceded his lifting of the globe from its cosmic context), they seem to

be superimposing their modern ex-post-facto view s upon the actual

sequence of the historical process: In actual fact it w as Copernicus’

freeing of the globe from its ties to the Aristotelian physical cosmos

which compelled his successors to carry th e critical revision of Aris­

totle’s physics to its ultim ate conclusion, after it had gene as far as it

presumably could on an essentially abstract level under the hands of

fourteenth century scien tists.14 Besides, there w ere enough novel phys­

ical ideas in the Copemican text to stim ulate such further investi­

gations. 15

In order to “lift” the earth out of the Aristotelian cosmos, Coperni­

cus needed an integral concept of the globe in which the elem ent water

no longer resided in a .separate sphere, but w as integrated w ith the ele­

m ent earth into a compact body. This w as in fact w hat the new geo­

graphic evidence permitted him to do. Y et he was undoubtedly aware

(as his phrasing occasionally indicates) that the relationship of earth and

water had formed the subject of an intense debate, from the thirteenth

14 In the actual sequence of the historical events it w as in fact the rec­ ognition of the earth’s dual m otion w hich (at least to a significant degree) led to the form ulation of the n ew doctrine o f “local m otion” by G alileo and others. The connection is stated in elem entary term s, e.g., in Herbert Dingle, C opernicus and th e P lan ets, in: A S h ort H isto ry of Science. A S ym posiu m (based on the BBC Third Program m e series), Doubleday Anchor Books, N ew York, n.d. (originally: 1951), pp. 24 f.; also H. B utterfield, op. cit., ch. 4: “The D ow nfall of A ristotle and P tolem y” (passim ). Cf. note 1 above (esp. M oody’s essay) for the essentially abstract treatm ent of the problem of motion in fourteenth century physics, w hich would seem to confirm th e suggestion that it was Copernicus’ theory that shifted the critique of A ristotelian physics to a n ew level w here m otion had to be considered as a universal phenomenon, subject to u niversally valid law s. If it is true (as, e.g., D ingle argues) that motion up to Copernicus w as considered exclu siv ely in reference to th e earth — towards or aw ay from its center w ithin the “sublunar region”, around the earth for the orbits of the stars — so that the phenom enon o f m otion (“natural” at any rate) w as conceived in the sam e geocentric term s as everything else in the A ristotelian cosmology, it m ust follow indeed that the concept of the m otion of the earth around itself and around the sun disrupted this entire fram ew ork and posed the problem of finding an entirely novel set of law s, w hich had to be developed, first of all, from the observation of free-fallin g objects, as a logical basis for the form ula­ tion o f any universal law s. (See also notes 19 and 26 below.)

The Influence of th e G eographic D iscoveries upon C opernicus 207

century — i.e. since the Latin translations from the Arabic had first

made A ristotle’s scientific writings available to a European public —

until the tim e of the high R enaissance.16 The problem had stirred up such

an amount of public interest that Dante is supposed to have read a paper

on the Quaestio de aqua et terra before a large audience in Verona in

about 1320 (the authenticity of Dante’s authorship has been doubted,

but the keen interest among the educated fourteenth century public has

not); and that tw o hundred years later Leonardo da Vinci w as still

entering thoughts about th e problem in his Notebooks. 17

The issue of this amazing debate had concerned A ristotle’s theory

about the sphere of water; m ore broadly the relationship of the ele­

m ents water and earth on the globe; and — still more basically — the

structure and the ultimate identity of the earthly globe as a whole. With

that one m ight say that the later Middle A ges and the Renaissance had

wrestled w ith the problem of defining the shape and nature of our

earthly habitat — perhaps a scientific expression o f the same tenden­

cies that led to glim pses o f the earthly environment in contemporary

literature and art; at any rate an intellectual current that m ight be con­

sidered as a forerunner (or in Leonardo’s case an unrelated accompani­

ment) to the geographic theory o f the age of discoveries. The debate had

opened w ith an essential re-statem ent of A ristotle’s view s in Sacrobosco’s

(John of Holy wood’s) popular treatise on the Sphere, early in the thir­

teenth century: In A ristotle’s view , as Sacrobosco summed it up, the

16 Copernicus repeatedly echoes them es w hich, w h ile they m ay go b ack to A ristotle’s ideas, w ere p ersistently discussed during th e M edieval debate and in fact form ed som e of its key topics: e.g., the relation of th e volu m e of w ater to that of earth (De rev., I, 3; see note 21 below); or that “for th e sa fety of livin g things, stretches of the Earth are le ft uncovered” (De rev., I, 3); or that th e air “contains an adm ixture o f earthy or w atery m atter” (De rev., I, 8). W hile th e latter idea sp ecifically occurs in the M eteorology (cf. note 11 above), sp ecu la­ tion on the tendency of w ater to m ix w ith earth is, e.g., one of the concepts discussed by Robertus A nglicus in his com m entary on Sacrobosco’s S ph ere (see note 18 below) and in Oresm e’s L im e du d e l e t du m on de (cf. note 19). Kuhn has m oreover noted a num ber o f basic Copernican ideas w hich had been an tic­ ipated by Oresm e (including th e theory of optical relativity).

17 The authenticity o f D ante’s Q uaestio de aqua et terra has been doubted, on som ew hat farfetched geographic grounds, by Bruno Nardi (but ascribed to an unknown fourteenth century author w ho supposedly took D ante’s name). I pro­ pose to deal w ith the problem m ore thoroughly in m y forthcom ing T errae In - cognitae article. Leonardo’s ideas about th e structure o f the earth w ere based on an evident w orking fam iliarity w ith fourteenth and fifteen th century ideas on the subject (from Buridan to A lbert of Saxony, Leon B attista Alberti, N icholas o f Cusa), yet seem to have am ounted to certain evid en tly original concepts based on direct observation and subsequent thought, i.e., a “dynam ic” relationship b e­ tw een earth and w ater, determ ined by the m igration of continents across geo­ lo gical tim e, as w e ll as by the corrosive effects of w ater on the structure of m ountains. He calls w ater “nature’s carter” (“il vetturale della natura”) and speculates on a sh iftin g volum e o f earth and w ater, due to their m ixing, esp. in coastal areas. (See V. P. Zubov, Leonardo da V inci, Engl, translation by D. H. Kraus, Harvard U niversity Press, 1968, pp. 239 f., 241, 230 f., w ith references to Leonardo’s N otebooks in their various m anuscript editions). It m ight be noted that Leonardo’s entries on these and related astronom ical problem s seem to have extended through th e tim e w hen Copernicus began his w ork on th e R evolu tion s (and perhaps u n til as late as 1518).

problem of conceiving both earth and water in terms of spheric shapes

resolved itself by thinking of the elem ent earth as a spherical inner ker­

nel, surrounded by th e sphere of water which in turn would be tanta­

mount to the globe. In both instances the perfect sphericity would be

marred by the mass o f the habitable land, w hich w as conceived as

a large-sized “protrusion” from the central kernel of the elem ent earth

and which, by the same token, reduced the surface of the sphere of

water by about h a lf.18 (In order to “save” the spheric shape of water

despite this substantial reduction of its surface, one w ould evidently

have to assume that the inner kernel o f earth w as comparatively small,

so that one could think of water as occupying m ost of the interior of the

globe.)

Though this would seem an ingenious solution to the problem, it did

not satisfy the M edieval mind. A spate of commentators, from th e thir­

teenth century to such leading fourteenth century scientists as Buridan,

Albert of Saxony and Nicole Oresme, began to question the Aristotelian

concept w ith remarkable freedom of critical thought. Their critical com­

ments seem largely to have been occasioned by the im plicit conflict

betw een the perfection of A ristotle’s scheme of spheres and the empiri­

cal (i.e. geographic) evidence which disturbed that perfection. Re-think­

ing th e scheme, on the slim basis of th e available geographic or geo­

physical facts, they began to question the validity of A ristotle’s whole

cosmic structure (Oresme, in his Livre du d e l et du monde, w ent so far

as to doubt that the elem ents occupy distinctly identifiable, separate

spheres); w hile another type of comment seemed to anticipate a more

compact, less rigidly divided conception of the globe (e.g. by proposing

that earth and water, according to actual observation, tend to “m ix”).

However, the entire three hundred year-long discussion (culminating

w ith Leonardo’s bold and inspired thoughts) w as decidedly hampered not

only by a lack o f n ew empirical evidence, but in particular by a pervasive

13 The S phere of Sacrobosco and Its C om m en tators, ed. and transl. by

L Thorndike, Chicago, 1949, contains significant segm ents of the debate during the thirteenth century, including Robertus A ngelicus’ ideas regarding the m ixing of earth and w ater (p. 205; see note 16 above). Sacrobosco d efinitely identifies the earth w ith the habitable land “about which is w ater”, thereby perpetuating A ristotle’s notorious vagueness concerning the id en tity of the globe. He projects an unm istakable picture of the sphere of land as inner core from w hich the three-continental land m ass protrudes across the w ater’s surface. Water and the rem aining tw o elem ents “in turn surround th e earth on all sides spherically, except in so far as th e dry land stays the sea’s tide to protect the life of anim al beings. A ll, too, are m obile excep t earth which... as a round body, oc­ cupies the m iddle of the sphere” (p. 119). The idea of “m obile” spheres of ele­ m ents seem s to h ave come from the M eteorology, w here A ristotle introduces certain “m otions” lik e rising and fallin g or the m ixin g of elem ents; cf., e.g., note 11 above. The idea that the habitable land m ass occupies approxim ately one h alf — or 180° longitude — of the earth’s surface occurs in P tolem y’s G eo­ graphy, w hich w as not exp licitly know n in the W est before 1410. H owever, any substantial land m ass on the surface w ould evidently h ave included the same basic requirem ents.

The Influence of th e G eographic D iscoveries upon C opernicus 209

confusion betw een the concept o f th e earth as a w hole and of

“earth” as an element, synonym ous — at least partly — w ith the known

habitable land mass. In the absence of fresh geographic evidence w hich

would have resolved that confusion — and opened up n ew perspectives

upon the w hole Aristotelian scheme — this long and am azingly lively

debate was therefore confined to a purely speculative level, on which

any new and original idea m ight be as true as again it m ight n o t .19

While the M edieval and Renaissance debate already reveals a remark­

able tendency for revising the Aristotelian cosmology on the basis of

facts known about the earth, it is clear that the chief obstacle to any

further substantial progress was in th e assumption that w ater constitutes

a separate sphere. As long as the known geographic data appeared to

confirm this crucial Aristotelian idea — i.e. as long as geographic theorists

and mapmakers were perpetuating th e notion of a two-part division of

the globe betw een th e “habitable land” and an impenetrable “Ocean

sea” — it w as virtually impossible to deny that “outer space” began at

the land’s edge and from there ascended in a harmoniously ordered suc­

cession of spheres towards the orbits of the sta r s.20 (It w as evidently the

18 Jean Buridan’s and his student A lbert of S axon y’s pertinent view s (from Buridan’s Q uaestiones su per lib ris q u attu or de caelo e t m undo, ed. E. A. Moody, Cambridge, Mass., 1942; and A lb ert’s Q uaestiones in A risto te lis libros de caelo e t m undo, Pavia, 1481, and his A cu tissim e qu aestiones su per libros de ph ysica ascultation e, Venice, 1504) are summ arized in V. P. Zubov, op. cit., 237 ff. (esp. their distinction betw een the cen tru m m agn itu din is and the cen tru m g ra v ita tis w ith respect to the earth), N. Oresme, Le liv re du d e l e t du m on de (Engl, version ed. A. D. M enut and A. J. Denom y, Madison, Wise., 1968, p. 569) d is­ cusses the distinction betw een the “geom etric cefiter” and the “center of gravity” in terms of the uneven distribution of w eigh t on the earth, in this context touching on the problem o f the resp. volum e of earth and w ater; (see n ote 16 above) and suggesting that the continents are m ade up o f a m ixtu re o f earth and w ater (a point m ade already by Robertus Anglicus, cf. notes 16 and 18 above). In re-exam in in g the A ristotelian schem e w ith the help of a diagram (p. 703), (“This seem s to be the design A ristotle had in m ind”, p. 705), Oresme, after som e discussion, concludes: “From these argum ents, therefore, I conclude and say, first, th a t th e elem en ts do not h ave the lim ite d and d istin c t areas or regions sta te d above, bu t th a t th e en tire distance b etw e en th e cen ter o f th e w o rld [equi­ valen t to the center of the earth] and the h eavens is in d ete rm in a te and in ­ d ifferen t to such division , e x c ep t th a t the h ea viest elem en t is or ten d s to be beneath the less h e a v y ” (p. 707). It m ight be noted that all Oresme has retained of the A ristotelian law s in this am azing speculation is the basic sequence of the elem ents, caused by their resp. “volu m e” or “w eigh t” (“h eaviest” against “less h eavy”), w hich determ ines their — otherw ise indeterm inate — sites w ith respect to the “center of th e w orld” (or of the earth, assum ing that these tw o coincide) and therefore their “natural” motion. Consequently, the recognition that the earth m oves as a planet — and that therefore its center does n ot coincide w ith the center of the universe — opened the w ay for a m ore fundam ental critique of the A ristotelian system than any of these earlier speculations had perm itted, by posin,g the problem of m otion in an entirely n ew context, i.e. outside the earth-centered fram ew ork of the A ristotelian cosm ology. (See note 14 above; also E. Rosen, “The D ebt of Classical Physics to R enaissance Astronom ers, particularly K epler”, Ithaca, 26 VIII, 2 IX 1962, pp. 81 ff., w ho already em phasized C opernicus’ contribution to early modern physics in this regard, including his new concept of gravity, as resu lting from the n ew astronom ical context). See also notes 27 and 28 below.

20 That the integration of the “sphere of w ater” w ith the “sphere of earth” into one solid concept of the globe represented the first and indispensable prem ise

same notion w hich'caused these vacillations betw een “earth” as an ele­

ment, identical w ith the known land, and earth as the earthly globe.

A true concept of the globe, in other words, could only develop once

the “Ocean” had been opened up for travel, and therew ith integrated

w ith the continents into one continuous entity). It was precisely on this

point that Copernicus, in his geographic chapter, introduced the new

geographic evidence, concluding that there no longer was any basis for

maintaining the idea of a separate water sphere, and asserting that the

globe as a w hole constitutes a solid body (or, mathematically, a “sphere”).

To m y knowledge, Copernicus’ chapter has never been subjected to

a complete analysis of its geographic content. This is adm ittedly a som e­

w hat difficult task, chiefly because his treatment of geographic prob­

lem s lacks th e kind o f synthetizing ability that would have been char­

acteristic of a professional geographer, w ith th e result that his meaning

appears at first often rather obscure. It is also difficult to see how the

chapter could be understood except in context w ith that preceding de­

bate, to which Copernicus is quite clearly (although only by implication)

referring. 21 The w hole point of the chapter is revealed in its heading:

“How the Earth, w ith the Water on It, Forms One Sphere”. In the first

paragraph he takes up the problem of the relation of water and land on

the surface of the globe — the very problem that had preocuppied the

M edieval Aristotelians, using virtually the identical phrasing that was

so often employed in the M edieval debate: “Thus, for the safety of

for Copernicus’ theory of the earth’s dual (esp. its planetary) m otion follow s from the analysis of his geographic chapter w ithin the con text of his heliocentric argu­ m ents. (See below , esp. note 25). By the sam e token, his n ew physical ideas con­ cerning m otion and gravity seem not only predicated upon his separation of the center of the earth from the center of the u niverse (cf. note 19 above), but again sp ecifically upon the concept of the globe as an integral, solid sphere. (See notes 26-30 below). For significant theoretical anticipations of the n ew global concept prior to the principal geographic discoveries, see m y G eography in 15th Cent. Florence. A ristotle’s vagueness about the identity of th e globe is perpetuated throughout the M edieval debate (including Oresme) and is evidenced by a per­ petual tendency of these comm entators to confuse “earth” as an elem ent w ith the terrestrial globe (a confusion w hich seem s in turn to have been perpetuated by their modern English translators).

21 It seem s evident that Copernicus considered the earth as a sphere in geo­ m etric terms, after having established its spherical nature on the basis of geo­ graphic evidence; cf. below , esp. note 25. This is clearly suggested by his use of the concept “sphere” in the chapters follow ing h is geographic discussion, despite his apparent vagueness regarding sphere as a geom etrical term w ithout physical substance and a threedim ensional body in a different con text (see note 6 above). On Copernicus’ apparent fam iliarity w ith the M edieval debate, see note 16 above. When Copernicus (De re v., I. 3) insists, e.g., that the volum e of w ater m ust be less than that of earth, he seem s to be w riting in ex p licit contradiction to Buri- dan, A lbert of Saxony and Oresme, all of whom had asserted the opposite; V. P. Zubov, op. cit., 237 f.; N. Oresme, op. cit., p. 569. Concerning Copernicus’ status as a geographer, I am indebted to Professor Joseph Babicz o f the Polish In stitu te for the H istory of Science and Technology, of the Polish A cadem y of Sciences, for his reference to Copernicus’ possible share in the m ap of Prussia; see also E. Rosen, Three C opernican T reatises, p. 4 (where the m ap is attributed solely to Rheticus). I hope to be able to investigate these leads further, in the context of a fuller discussion of Copernicus’ attitude towards geography.

The Influence of th e G eographic D iscoveries upon C opernicus 2 1 1

living things, stretches of the Earth are le ft uncovered.” 22 But the im ­

portant difference is that Copernicus here sketches a picture in which

the “stretches... left uncovered” no longer refer exclusively to a single

coherent three-continental land mass (as they had for the M edieval com­

mentators or on earlier maps), but, in addition, to “numerous islands

w idely scattered”. In fact, he goes on: “Nay, w hat is a continent, and

indeed the w hole of th e Mainland, but a vast island?” And later on in

the chapter, in his reference to the discoveries, he speaks explicitely of

“th e islands found in our own tim e under the Princes o f Spain and

Portugal, particularly America, a land . . . on account of its size, reckoned

as another Mainland.” In short, the surface of th e globe is presented

as a continuous alternation of land formations w ith extended stretches

of sea, in w hich one m ight think of the continents on th e order of

“vast islands” and where the continents (or “islands”) specifically

include the N ew World.

With this diversified picture of the earth’s surface as a starting

point, Copernicus proceeds to explode the theory of the sphere of

water: If it w ere true that the globe consists m ainly of w ater — a con­

cept w hich the idea of a separate w ater sphere necessarily involves, as

w e noted above — the land m asses would in fact have to be confined

to one major, coherent “protrusion” from the inner kernel of earth. The

very fact that the surface shows a continuous alternation betw een land

and sea (including “the Mainland of America [which] on account of its

position [must] be diametrically opposite to the Ganges basin in India”)

must mean that the globe consists chiefly o f solid m atter and that water

is essentially lim ited to th e surface, w here it “form[s] the seas and fill[s]

the lower declivities”. 23 Despite his comparative unfam iliarity w ith the

22 I hope to be forgiven if for the sak e of exp ed iency I am using K uhn’s English translation here (op. cit., pp. 146 ff.). The forthcom ing article in T errae Incognitae w ill include the Latin text, from th e Toruń ed.

23 I have cited Copernicus’ text, at least in part, outside o f its actual context. (E.g., “The w aters spread around the earth form the seas and fill th e lower d eclivities” appears in the opening of the chapter). My purpose (inevitable in an interpretation) w as to reconstruct his m eaning by singling out his salien t thoughts. Since his com parative u nfam iliarity w ith global geographic issues seem s to have resulted in a certain lack of organization, so that his ideas are presented in a som ew hat ram bling and not alw ays logically connected w ay, it seem ed in ­ dispensable to try to restore his logic by occasionally disregarding the actual sequence of his argum ents. His m ost direct attack on the id ea of the globe as m ade up m ostly of the sphere of w ater consists in the statem ent that if the globe w ere predom inantly water, “the depth of the Ocean w ould constantly in ­ crease from the shore outwards, and so neither island nor rock nor anything of the nature of land would be encountered by sailors, h ow far soever they ventured.” W hile the statem ent in this phrasing is not n ecessarily cogent (even if the land m ass w ould be a coherent “protrusion” from a com paratively sm all inner core of “earth”, occasional minor offshoots in the shape of sm all land form ations — and even large form ations, in an enorm ously com plex geom etric shape — could theoretically still be conceivable), Copernicus is of course sub­ stantially correct: The fact of a frequent alternation of sea w ith land form a­ tions, including several unconnected continents, on the surface of th e earth w ould indeed reduce the idea that the interior of the globe consists m ostly of w ater, surrounding a sm all central core of solid matter, to an extrem e im ­

handling of global geographic problems, Copernicus has drawn a perfectly

logical conclusion from the new geographic evidence concerning the

structure of the earth. The old two-partite division of the earth — older

than Aristotle, in fact as old as the first known maps — has given w ay

to a “compact” concept of the earth; and the separate sphere of water

has been abolished, both on incontestable empirical grounds.

Let m e end this paper by expressing m y conviction {a) that this new

global concept plaid a significant role in the logical development of

Copernicus’ thinking; (b) that the analysis of this chapter therefore

highlights his logic, in handling the non-astronomical premises of his

theory, much more convincingly than has been recognized so far; and

(c) that his awareness of the far-reaching physical implications of his

probability (i.e,. as long as the land form ations are supposed to b e connected w ith that inner core). I think that his n ex t — otherw ise virtu ally u n in telli­ gible — sentence m ust be understood in the sam e context, i.e, as an em pirical exam p le in support o f this argument (“Yet, w e know that betw een the Egyptian Sea and the Arabian Gulf, w ell-n igh in the m iddle of the great land mass, is a passage barely 15 stades w id e”). By pointing to th e extrem e exam ple of the narrow sea passage betw een the A sian and African continents, w est of the Gulf of Aden, “w ell-n igh in the m iddle of the great [i.e. coherent three-continental] land m ass”, Copernicus evidently w ish es to supply a drastic illustration for the continuous alternating betw een land and sea form ations, and thus to bolster his thesis that w ater is confined to the surface of the globe. This is follow ed by the further argum ent that “modern discovery” (in the Far East) has added an area of as m uch as 60° in longitude to the 180° extension w hich Ptolem y had postu­ lated for the habitable world. “Thus w e know that the Earth is inhabited to a greater longitude than is left for the O cean”. It is in this content that Coper­ nicus turns to the “islands found in our own time..., particularly A m erica”. Though I find it d ifficu lt to pin down Copernicus’ geographic inform ation which m ay h ave led him to this conclusion, it is evident that he is using this pre­ sum ptive evidence in further support of his m ain thesis (i.e). that the exten t of land form ations on the surface of the globe precludes — or at any rate severely reduces — the p ossib ility of a globe consisting m ainly of water, an argument w hich is in fact greatly strengthened by the existen ce of the American con­ tinent). Conceivably Copernicus realized that in strict geom etrical term the existen ce of num erous land form ations need not absolutely preclude the idea of an essen tially w ater-filled globe, but m erely m akes it extrem ely u nlikely, and therefore tended to augm ent his “em pirical evidence” regarding the surface area occupied by land. (G eographically, the statem ent — in effect arguing a tw o- thirds surface area o f continuous land versu s one third occupied by sea — w ould seem to presuppose a severely foreshortened idea of the circum ference of the globe, presum ably the one traditionally attributed to Poseidonius, which w as in fact quite com m only accepted in the earlier R enaissance geography; as w ell as an essen tial ignorance of the distribution of land and sea in th e South­ ern Hemisphere; and specifically an essential ignorance of the exten t of the Pacific; as w ell as, lastly, an exaggerated idea about the Eastward extension of the A sian continent. I am therefore inclined to conclude that the statem ent re­ flects in fact a world map produced prior to the return of M agellan’s V itoria in 1522, such as W aldseem ueller’s of 1507 or Joannes de Stobnicza’s of 1512, based on the in set in th e W aldseem ueller’s map, both of w hich show indeed an Eastw ard extension of the A sian continent to 240° longitude, w hich would tend to confirm that Copernicus w rote the chapter around 1512; see n ote 5 above). The term “modern discovery” w ith regard to the areas of the Far East m ay refer to the report of the voyage of N. de Conti; see m y G eography in the 15th Cent. Florence, pp. 20 f.

For all its occasionally questionable use of geographic evidence, the chapter w ould seem to show Copernicus as basically accurate in his interpretation of the n ew geographic data, as they w ere know n by about 1512, for a substantially changed concept of the globe.