The Heated Battlefield of the History of Maritime Discoveries


Western history is a true battlefield when it comes to certain decisive advances in science and civilisation. The reason being that Western historians suppress the real author of such advances, the Muslims, and then, in seeking to substitute alternative authors, each  group of historians comes up with explanations, which hold no historical ground.[1] The following highlights this matter. 



A large group of historians categorically assert that Ptolemy’s science was central to maritime discoveries, that between Ptolemy and the 14th century there was hardly any advance in the field, and that the only map of the Mediterranean  of any worth was that of Ptolemy.[2]

This is fundamentally wrong, the above sections on mapping, and earlier chapter on astronomy have shown how Ptolemy’s maps and measurements were wrong, and that every Islamic scholar corrected his measurements. Thorndike, who has studied the matter comprehensively, rightly concludes that Ptolemy’s geography:

‘Consists largely of lists of ancient place names, many of which cannot be identified or located with any assurance and are of purely historical and linguistic interest. Moreover, Ptolemy had made the Mediterranean  Sea too short[3] by one third (Thorndike should have said too long), whereas one of the medieval portolani is more accurate than any other map of the Mediterranean until the eighteenth century. Concerning the Far East, too, and islands in the Atlantic, the thirteenth and fourteenth centuries were much better informed than Ptolemy. The translation and subsequent vogue of his Geography were therefore in some ways regrettable.’[4]



Like Thorndike, a substantial group of Western scholarship is very critical of Ptolemy. Parry, for instance, says:

‘In the process of Reconnaissance, explorers by sea, pushing rashly out in the world of the unknown, but for Ptolemy, and finding it bigger and more varied than they expected, began first to doubt Ptolemy, then to prove him wrong in many particulars, and finally to draw on maps and globes a new and more convincing picture. Similarly, but independently, Copernicus and his successors, studying their Ptolemy and watching the heavens, noticed certain celestial phenomena which Ptolemy’s theories failed adequately to explain. They began timidly and tentatively, first, to question, then to dismantle the Aristotelian geocentric scheme of the universe, and to postulate a heliocentric system in its place. In both studies, the whole progress from deferential acceptance to doubt, from doubt to discard and replacement, took many years. Eventually in all branches of science, Reconnaissance became Revolution.’[5]

This is a thorough refutation of Ptolemy’s contribution to maritime discoveries by Parry, but his account, just like the rest of his counterparts, includes many fallacies and distortions, too. First, as this section will show below, the seas and oceans hardly remained unknown between the time of Ptolemy and the ‘Renaissance’ as Parry tells us. Secondly, Ptolemy as was shown in the preceding heading was amply corrected centuries before the men of the Renaissance. Had Parry also, however briefly, consulted a work by Wright, four decades earlier than his, he would have found that amongst the followers of Muslim geographers/astronomers was Raymond of Marseilles (fl 1140s). In the preamble to a set of tables for Marseilles, worked over from al-Zarqali’s canons on the Toledo  Tables (in 1140), we find a detailed rule for the construction of tables for other meridians than that of Marseilles and at the places for which the tables wanted.[6]

The material to correct Ptolemy’s maps was available centuries before the Renaissance.

Furthermore, a vast knowledge of Muslim geography, in its diverse forms, had already impacted on Western Christian knowledge in the Middle and Later Middle Ages. Without going into detail, Roger Bacon (1220-1294), the author of Opus Majus, quoted Muslim authorities in great abundance, especially Abu M’ashar, al-Farghani, Al-Battani , Al-Zarqali, etc, and reproduced their ideas on the planetary system, ocean tides, phases of the moon, the calculation of latitudes and longitudes, and their conception of the ‘Cupola of the Earth,’ or Arin[7] (the word Arin is a misreading of the Arabic transliteration of the Indian town Ujjiyaini).[8] Cardinal Pierre d’Ailly (1410) also quotes the Arin theory in his Imago Mundi, and it was this work which inspired Christopher Columbus in his view of the shape of the earth as a pear, and so that in the western hemisphere, opposite ‘the world summit,’ which he located somewhere near the mouth of River Orinoco.[9] This was one of the many ways Muslim learning impacted on the discovery of the New World, as will also be amply shown further on.

With regard to Copernicus, it has already been amply shown that his inspiration was from the 13th century Muslim astronomers such as Ibn al-Shatir of Damascus .[10] Moreover, Copernicus studied at Cracow, and this university’s learning was based on Islamic science, and authors such as Al-Battani , al-Farghani, Al-Ghazali , etc,[11] and not on a copy of Ptolemy, which would have completely misled him (Copernicus) had he stuck by it.



Another group of ‘historians’ steps in, and delivers us another set of explanations for the maritime discoveries. Chaunu, for instance, says:

‘All this unconscious preparation for discovery resulted with the amazing intellectual changes which took place at the end of the 12th century. It followed from the rediscovery of ancient science and then its outstripping by the use of Aristotelian method.’[12]

This is fundamentally ridiculous to say the least, for one can ask: why did neither Greece or Byzantium make the maritime discoveries Chaunu refers to if Aristotle (384-322 BC)  was the key? Why, if Chaunu is talking sense did no scholar understand the earth was round by just reading Aristotle in any century (fifteen of them) that elapsed before the 12th century? What is the contribution of Aristotle to the real means which made nautical discoveries possible: portulans, sails, the compass, new methods of calculation, improved measurements and knowledge of the earth and seas, etc?



Another group of ‘historians’ tells us that all maritime discoveries stem from the recovery in the 12th century of Greek ship construction techniques after such techniques had been lost for over ten centuries. Casson, thus, gives ‘the irrefutable proof’ of Greek use of lateen sail through the evidence of a 4th century piece of mosaic which seems to show a Greek lateen rigged boat.[13]  

This point brings us, again, to the inexhaustible list of items and scientific achievements, possibly hundreds of them, lost for over ten centuries, before, by chance, all were rediscovered by miracle in the crucial 12th century, the ridiculous view held by many, not to mention the other piece of poor ‘scholarship,’ that a piece of mosaic could be evidence enough to build a whole theory around it.



Then we have the Portuguese group of nautical geographers who tell us that none of what the other Western historians say is right; that instead, maritime discoveries are owed to Portugal, and to one man, in particular, Henry the Navigator, the father of modern nautical sciences. Hence, Cortesao writes:

‘The Portuguese were the designers and founders of nautical science in the 15th century, and until the first quarter of the 16th century they were unrivalled by any other people in its development and progress. From other people they received, however, the scientific preparation which constituted the background of their performance. Their merit lay above all in the fact of giving a practical application to a branch of scientific knowledge (astronomy, use of the astrolabe..) that had been used for speculative purposes only, thus solving a problem on the solution of which depended the progress of mankind. With the foundation of nautical science- a first step only in the great age of discovery of which they were the leading artisans-the Portuguese came to play a leading role in the Renaissance.’[14]

To reinforce one of his principal arguments, the Portuguese use of instruments for practical purposes, Cortesao quotes a Spanish pilot of the early 17th century:

‘Spaniards, French, English and Dutch owe what they know to the Portuguese, who taught them how to navigate on the high seas and in distant regions: to them not only Spain, but the whole of Europe owes the application of the astrolabe, which the ancient always used in order to know the movement of stars, to the use of art of navigation-such a great invention as its consequences show.’[15]

Cortesao and the Portuguese ‘school’ are very much nearer the truth than any other group of scholars with regard to nautical discoveries. And so are the Spaniards, who also insist on the role of the Iberian Peninsula in such discoveries, and, facts prove their case. Both Portugal and Spain played the leading role in maritime discoveries, for it was they who discovered the Americas, the route round Africa, the route to India , and so on and so forth. Where one disagrees with this Iberian school is when they bypass, except by vague remarks, the role of those who preceded them in setting up the foundations for Spanish and Portuguese discoveries, or when they make historically false statements as follows.


Cortesao, for instance, after reminding of one of the usual myths: ‘Arab pirates from the North Africa n coast growing more daring, infesting the Mediterranean , keeping navigation in these waters at their mercy,’[16] adds:

‘Arab geographers had spread the legend that beyond Cape Bojador (260 6’N) there was the Sea of Darkness and that torrid zone which would turn black any man who dared to penetrate into it. When the Portuguese (of course) doubled Cape Bojador in 1435 and reached Garnet Bay (240 51’N,) they not only dispelled a centuries old legend of terror but opened a new age in the history of navigation.’[17]

Of course Cortesao makes wild statements without providing any source for either of his assertions, just as he fails to do for others. Generalisations which are not backed by historical reality, either. Had Cortesao explored the history of his country, he would have read of those ‘Arab’ sailors who departed from his own capital, Lisbon, when it was in Muslim hands, in the 9th century, in the direction of unknown lands and, rather than telling of men turning black, instead, provided good descriptions of lands, including of the Canaries Islands, which the Portuguese were to only discover for themselves centuries after Muslim sailors had already described them.[18]

Cortesao also makes a serious mistake, when he says:

‘The Muslims used astronomical observations for astrology, and it was specifically for this purpose that it passed into Spain and Portugal… There is no reason to assert, as some have done, that any goniometric instrument was used to determine latitudes at sea before the second quarter of the 15th century. Certainly not in Europe. It is true that when Vasco da Gama arrived in the Indian Ocean  he found that the Arab pilots could determine the astronomical latitude at sea by means of a rudimentary apparatus of their own; but the process was inferior to that used by the Portuguese, we do not know when it began, and it never spread to Europe.’[19]

Again, he is not backing his statements by references, making generalised assertions, which do not hold scientifically. And he is also wrong on many accounts. First, how can Cortesao be sure instruments were ‘never’ used at sea in Europe before the Portuguese? How can he be sure the Muslim techniques of navigation in the East ‘never’ spread West?[20] Cortesao would have to be the greatest reader of the past, to make such assertive statements, and not to back them with any evidence. Secondly, had Cortesao enquired just a little on Muslim sciences and civilisation, he would have found that processes found East were also common West, with variations, of course, but knowledge was shared East and West of the Islamic realm in respect to nearly every matter, learning, technology, construction, arts, gardening, farming, trade, etc. Pilgrimage , travels of sailors, traders, scholars, exchanges of diverse sorts, through caravans, diplomatic and political channels, teaching, etc, all united the Islamic world in a common heritage.[21]  Moreover, when Cortesao says that the astrolabe was passed by the Muslims to Spain and Portugal for astrological purposes only,[22] he tells a fallacy. Had he explored the usage of the astrolabe by the Muslims, he would have found it included countless uses for the solution of practical problems.[23] Had he looked at the 10th century Spanish Catalan use of the astrolabe, inherited from the Muslims, for instance, he would have found it was used in practical matters such as land surveying. The 10th century Geometria incertiauctoris, which Millás Vallicrosa relates to the Arabized scientific corpus of the Monastery of Ripoll (in Catalonia),[24] details a variety of triangulation procedures that can be effected with the astrolabe, including the measuring of height and distance by right-angled triangles and squares.[25] The astrolabe was used in astronomy, of course, but also in navigation.[26] And had Cortesao read history properly, he would have come to the single conclusion: the Muslims did not need to pass the uses of the astrolabe to either the Portuguese or the Spaniards: the Muslims were part and parcel of the history of these countries, and their legacy, including of the use of the astrolabe, astronomical learning, etc, was just assimilated alongside the rest of the Islamic heritage. Among those who inherited such learning was Alfonso the Wise (King of Castile 1252 to 1284), whose Liber del saber Astronomica, as Cortesao fails to say,[27] was based on al-Zarqali,[28] and that Al-Sufi, who wrote on astrolabe uses, was also the source of the Alfonsine tables.[29] Moreover, Denis of Portugal (1261-1325) was by no means as innovative as he (Cortesao) implies,[30] but was an adept of Islamic learning, Denis ‘doing for his country what Alfonso the Wise had done for his own a little earlier.’[31] As for the idea of using instruments for determining latitudes at sea, it did not come naturally to the mind of Prince Henry’s cosmographers, [32] but had come to Muslim minds earlier than theirs.[33] Cartography did not develop pari passu with Portuguese navigation, either, as Cortesao says, speaking of ‘ample evidence’ to prove his point, without citing such evidence,[34] but contrary to what he says, and as the previous heading has shown, cartography developed centuries before the Portuguese amongst Muslims. Just as nearly every aspect of nautical science is owed to the Muslims as is now shown.

[1] A good instance of this relates to the rise of Provencal literature and romance. See M R Menocal: The Arabic Role in Medieval Literary History (University of Pennsylvania Press, Philadelphia, 1987).

[2] Commentaries following lecture by R. Almagia at the Lausanne Congres; in Archives Internationales d’Histoire des Sciences; vol 1; pp. 237-46, at p. 245.

[3] Throndike is wrong, Ptolemy made it too long.

[4] L. Thorndike: Renaissance or Prenaissance; in The Making of Modern Europe; edited by H. Asubel; Book One (The Dryden Press; New York; 1951), pp. 60-72. p.63.

[5] J.H. Parry: The Age of Reconnaissance; op cit; pp. 14-5.

[6] Bibliotheque Nationale; Ms. Fonds Latin ; n. 14704; fol 116. col c. in J.K. Wright: Notes on the Knowledge of latitudes and longitudes in the middle ages; ISIS 5; pp. 75-98; at p. 83.

[7] M.S.Z. Alavi: Arab Geography; op cit; p. 111.

[8] J. H. Kramers: Geography, op cit,  p. 93.

[9] M.S.Z. Alavi: Arab Geography; op cit; p. 111.

[10] N. Swerdlow-O.Neugebauer: Mathematical Astronomy in Copernicus ‘‘De revolutionibus'' (New York, Springer Verlag, 1984).

[11] A. Brikenmajer: l’Universite de Cracovie, Centre International d’Enseignement Astronomique a la fin du moyen age. In Studia Copernicana, 4; 1972; pp. 483-95; or see: J.B. Korolec: La Premiere reception de la philosophie Islamique a l’Universite de Cracovie; in The Introduction of Arabic Philosophy; op cit; pp. 112-30.

[12] P. Chaunu: European Expansion in the Later Middle Ages; tr. by K. Bertram (North Holland Publishing Company; Amsterdam; 1979), pp 84-5.

[13] L. Casson: Ships and Seamanship in the Ancient World (Princeton; 1971); p. 244; and fig .182.

[14] A. Cortesao: Nautical Science and the Renaissance; in ARCHEION; vol 2; pp. 1075-92; at p. 1077.

[15] Thome Cano in Arte para fabricar, fortificar y apareiar naos de Guerra y mercantes…. (Seville , 1611), in A. Cortesao: nautical Science; p. 1088.

[16] A. Cortesao: Nautical; p. 1080.

[17] Ibid.

[18] See summary of these voyages of discovery in D.M. Dunlop: Arab Civilisation; op cit; pp.160 ff.

[19] A. Cortesao: Nautical; p. 1084.

[20] Ibid; p. 1085.

[21] See, for instance, G. Sarton: Introduction; op cit, on the countless instances of shared knowledge between the Muslim East and West.

[22] A. Cortesao: Nautical; op cit; p. 1085.

[23] H.N. Saunders: The Astrolabe; op cit;  p.7. W. Hartner, ‘‘The Principle and use of the astrolabe,'' op cit; and J.D. North: ‘‘The Astrolabe,'' op cit.

[24] In T. Glick: Islamic and Christian Spain; op cit; p. 228.

[25] Ibid.

[26] See: W. Hartner, ‘The Principle; op cit; pp. 287-318; and J. D. North: ‘‘The Astrolabe,'' op cit;  pp 96-106. 

[27] A. Cortesao: Nautical; op cit;  p. 1086.

[28] W. Hartner, "Asturlâb," Encyclopaedia of Islam; New series; I: 722-8; J. Millás Vallicrosa:  "Introducción del cuadrante con cursor"; M. Destombes, "Diffusion des instruments scientifiques," pp. 36-38, 41;  Salvador García Franco, Catálogo crítico de astrolabios existentes en España (Madrid: C.S.I.C., 1945); etc.. all in T. Glick: Islamic, op cit; p. 267.

[29] H.J.J. Winter: Notes on al Kitab Suwar al-Kawakib (of al-Sufi); in ARCHEION; Vol 8; pp. 126-33; esp. pp. 130-1.

[30] A. Cortesao: Nautical; op cit; p. 1086.

[31] G. Sarton: Introduction; Volume III; op cit; p.61.

[32] A. Cortesao: Nautical; op cit; p. 1086.

[33] Refer to following heading; see also, M. Destombes criticism of G. Baujouan; E. Poulle: Les Origines de la navigation astronomique au 14 em et 15em siecle; in Le Navire et l’Economie maritime du 15em au 18em siecles; Paris; 1957. Rev by M. Destombes; ARCHEION;  13; pp. 144-5. at p. 144.

[34] A. Cortesao: Nautical; op cit; p. 1087.