onésimo t. almeida
;
Portuguese navigators of the fifteenth and sixteenth centuries produced a significant body of literature—mostly logbooks and manuals—that is not well known outside Portugal. Some of these documents have never been translated. Others have received little attention because they appeared in editions with limited circulation among historiographers of science in the English-speaking world.1 Taken as a whole, this literature constitutes
an important contribution to our understanding of the transitional years between the Middle Ages and modernity. A close analysis of these writ- ings, of the trials and errors of the agents directly involved in the process, confirms that certain important developments in Portugal helped pave the way for modernity and the development of an experimentalist atti- tude toward the world. If so, the grand narratives that usually jump from the Islamic developments of science to the English contribution leave out a missing link, a remarkable web of activity and thinking that helps us realize that the seventeenth-century scientific revolution actually took a few centuries to develop, with the Portuguese navigators at the forefront of the process. Taken as a whole, these works support the idea that the transformation of the medieval worldview into the modern one was slow and geographically more widespread than is usually considered.2 I dare
say that if Francis Bacon’s Novum Organum,3 a classic considered to be
the great herald of the modern mind, is read in light of the developments that took place in Portugal prior to its publication in 1620, it will ap- pear more as a synthesis of the transformations that had been occurring
in Europe rather than the revolutionary work it is assumed to be.4 (On
Bacon and the reception of early-seventeenth-century Spanish geographi- cal discoveries, see Sheehan in Chapter 12.) Bacon himself said of the sea travelers of the times before him:
We must also take into our consideration that many objects in nature fit to throw light upon philosophy have been exposed to our view, and discovered by means of long voyages and travels, in which our time have abounded. It would indeed, be dishonorable to mankind, if the regions of the material globe, the earth, the sea, and stars, should be so prodigiously developed and illustrated in our age, and yet the boundaries of the intellectual globe should be confined to the narrow discoveries of the ancients.5
In another passage, Bacon includes navigation in his enumeration of advancements unknown to the ancients, a list that counts printing, gun- powder, and the compass among strides that, “have changed the appear- ance and state of the whole world.” From these novelties, “innumerable changes have been thence derived, so that no empire, sect or star, ap- pears to have exercised a greater power and influence on human affairs than these mechanical discoveries.”6
During the majority of the fifteenth century, the Portuguese improved, to a remarkable degree, inherited navigational technologies. Necessity was the impulse for the finding of new means to carry out navigation on the high seas, for the observation and registration of prevailing pat- terns of hitherto unknown winds, for the discovery of Atlantic currents, and for the mapping of the stars of the Southern Hemisphere to guide their way in the waters thereof (see Figure 4.1). They were obliged to construct better naus (ships) to adapt efficiently to new circumstances. Maps of the African coasts were elaborated, registering innumerable and important details for future voyages. All this was possible only thanks to an accentuated development, a progression of a spirit of observation, great care in research, and recording of a wide, diverse range of useful and important information. Over time, the idea was enshrined that data collected by seamen and through experience possessed greater validity than that of the “mathematicians” on land, the intelligentsia with ties to the royal court, or those who obtained most of their knowledge of mari- time exploration from ancient tomes with little in the way of fact. This new mentality was firmly instilled in a small elite that elaborated notable theories about the epistemological superiority of empirical knowledge.
Key among the Portuguese entrepreneurs of the maritime discoveries were Duarte Pacheco Pereira (ca. 1455–1530?),7 D. João de Castro (1500–
1548?), Pedro Nunes (1502–1578),8 Garcia de Orta (1490–ca. 1570), and
Fernando Oliveira (ca. 1507–ca. 1585).9 The work of other figures such
the maritime discoveries.10 Of this elite set, the names Duarte Pacheco
Pereira, Fernando de Oliveira, and Garcia de Orta stand out for having written largely about the importance of experience. Francis Bacon himself was not aware of their work. He was informed about the great impact of the discoveries, but he lacked closer information that would allow him to understand that such a complex process did not happen by accident, nor simply thanks to the courage of intrepid navigators, but because in their enterprise they developed and followed ground rules elaborated and improved upon by their own experience.
The leitmotif in authors such as Duarte Pacheco Pereira is, “experi- ence is the mother of things,” with frequent statements being made that point to the superiority of knowledge acquired from firsthand experi- ence—“experience has shown us that this is not so,”11 or, “experience
has disabused us of the errors and fictions which some of the ancient cosmographers are guilty of.”12
Aristotle had of course theorized clairvoyantly on experience, bring- ing the Greek conception of science to an impressive level. It was not, however, the Aristotelian empirical outlook that prevailed in the late Middle Ages and that became the established philosophical dogma. His philosophy had been somewhat turned on its head, and experience disappeared from its foundation. There were various brilliant spirits throughout medieval times who, on their own, recovered experience as a key foundation of the edifice of knowledge (Roger Bacon and Robert Grosseteste are just two examples), but when the Portuguese entrepre-
figure 4.1. Astrolabe, 1555
source : António Estácio dos Reis, Medir estrelas [Measuring Stars] (Lisbon: CTT, 1996). By permission of the author. From the collection of McManus Galleries, Dundee, Scotland.
neurs looked in the books of the Ancients for information about the oceans and lands overseas, they mostly gathered myths, or rather facts that they demonstrated through their own experience to be mere fables and myths. Aristotle, for instance, was a great biologist because he based his writings about animals on empirical evidence. However, he did not venture much out of Athens, and as a result most of his cosmological descriptions were the result of armchair philosophy or hearsay.
Having written elsewhere about the overall contributions of these au- thors,13 I wish to concentrate here on the particular working relationship
that existed between two of the above-mentioned figures, Pedro Nunes and D. João de Castro. Their example will challenge the received view that so-called scientific activities in the 1400s and 1500s were conducted in isolation and with no bearing on real-life problems.
Indeed, the figure that stands out the most in formulating a “new” theory of knowledge is that of D. João de Castro (1500–1548) (see Fig- ure 4.2).14 Born in Lisbon, he was a naval commander who wrote a cos-
figure 4.2. Portrait of Dom João de Castro, Paris, 1833
source : Dom João de Castro, Roteiro em que se contem a viagem que fizeram os
mographical treatise, Tratado da sphaera por perguntas e respostas a
modo de dialogo (Treatise on the Sphere Through a Dialogue of Ques-
tions and Answers), probably written before 1538 (see Figures 4.3 and 4.4). Of greater importance for our purposes are his three Roteiros (log- books), in which important events occurring in his voyages are recorded. The voyages are from Lisbon to Goa (1538), from Goa to Diu (1538), and from Goa to Suez (1540–41). In 1545 he returned to India as a viceroy.
Castro not only theorizes about the role of experience in the process of knowledge acquisition, but he also reaches further, pointing to the limits of the senses whose errors must be corrected by judgment. Castro is indeed the most modern of the maritime travel writers of this period. He reveals a strong empirical mind, takes meticulous notes, undertakes experiments alone and with his crew, takes measurements and double-checks them, and attempts to make sense of the data collected. These are impressive signs of a rather modern mind at work. He goes further, however, reflect- ing a concern with theory as well as with experience, and advocates for a dialogue between both.15 (For the Spanish aspects of this dialogue be-
tween experience and theory, see Portuondo’s essay in Chapter 3.) The other figure to be highlighted here is Pedro Nunes. Born in Alcácer do Sal in 1502 to a New Christian family, he became a math- ematician and was considered one of the greatest of his time. Best known
figure 4.3. Page from D. João de Castro, Tratado da sphera, 1537
for the invention of the nonius (an instrument named after his Latin name), he made important contributions in the area of technical naviga- tion, but he was also the most theoretical of all the authors and thinkers involved in the process of the discoveries. The interactions and exchanges he had with D. João de Castro provide for an impressive example of co- ordination between theoreticians and practitioners, with Nunes staying on land, collecting data and information, theorizing, and attempting to make sense of things, while Castro was out at sea, facing problems of all sorts. These interactions are emblematic of the relationships maintained by the leaders and masterminds, thinkers and entrepreneurs involved in the overseas voyages of discovery.
The philosopher of science Ernan McMullin affirmed in a presidential address to the American Philosophical Association that, “the goal of technical control played virtually no part in the origins of science.”16
A reading, even a superficial one, of the Roteiros of D. João de Castro would constitute a legitimate point of departure for us to question Mc- Mullin’s assertion. It will serve equally as a call to attention for the his- torians of science to the scientific activity (in the modern sense of the term) that took place in Portugal during the period of the discoveries.17
The focus of this essay will be limited to the interaction between theo- rists and navigators and will evaluate their success or failure in achieving greater certainty as to the movement of ships, as well as making further advances in the dominion of the seas. Let us begin with the Roteiro de
Lisboa a Goa (Rutter from Lisbon to Goa). Pedro Nunes had conceived
of two “shadow instruments”—one to measure the altitude of the sun and the other to calculate the magnetic declension (see Figure 4.5). The mathematician was not, however, a sailor; he sought only to respond to the needs expressed by the navigators, who, upon returning from their voyages, brought him questions, qualms, and new data that called into question previous explanations and, in some cases, revealed that the in- struments created by Nunes himself were difficult to use, if not totally useless. The description of the voyage in the vicinity of the island of Porto Santo reads:
Saturday, April thirteenth, at dawn we saw the palm, that is one of the Canary Islands, and at once I made ready the lamina and shadow instrument, which I owe to the graciousness of his highness prince D. Luís,18 with a great desire to verify
two things: the first, if on these islands the needles varied or not, as the practice of many pilots at this place and meridian would make the north of their needles on the true pole of the world; and the second, if it was true and accurate the rule given to us by the doctor Pero nunez that, at all hours of the day in which shadows ap- pear, we know the elevation of the pole; with which instrument I made the follow- ing observations, the wind being calm all day, such that the ship did not sway.19
Later on, Castro records two measurements and adds that he then, “ordered the pilot to calculate the altitude of the sun at midday, and [moved] to the armillary sphere, in order to verify the elevation of the pole of this day.”20 Following this is a meticulous description that is
worth transcribing in detail, as it reveals a truly rigorous methodologi- cal approach:
Firstly, on the graduated horizon of the armillary sphere, I recorded the variation made by the shadow of the pointer from the first altitude to the second, the varia- tion of which was seven degrees, and the very first of these seven degrees were set on the horizon, I recorded the first altitude; and it was 57 degrees for one graduated meridian above, and in the place where the number of these 57 degrees ended, I put a point; and going over the same meridian on the other extremity of the variation of the shadow that I recorded on the horizon, I counted by the meridian upwards to the second altitude, which was 61 degrees and 1/2, and in the place where they ended I put another point.
He continues to describe his method, and concludes by conferring with his pilot in order to confirm his findings:
I then sent this altitude to the pilot in a sealed note, so that after he calculated the altitude of the sun at midday we could see both of them together, without suspicion (and thus) we would be able to determine how much mine, taken in the morning, differed from his, taken at midday. Now the pilot, having finished calculating his altitude, came to me and said that we were at an altitude of 29 de- grees and 1 /3, and immediately opened the note and saw mine, at which he was quite startled.21
Particularly noteworthy is Castro’s preoccupation with temporarily concealing the data he had obtained, in order to compare it later with that of the pilot without danger of influencing the measurements of the latter. Meanwhile, he proceeds with his own measurements, making clear that he utilizes the aforementioned shadow instrument in order to verify the declension of the needle, exactly as Pedro Nunes had advised him.22
Further on, on April 21, D. João writes:
Because I make mention many times of the altitude taken by many people, and expect to do so later on, already it may be that those who read this Roteiro, find- ing considerable the difference between some altitudes and others, could think that this diversity would come from having tables of different declensions, or from erring in the calculations; therefore I will always make mention of the alti- tudes they take of the sun at the horizon, and thus declare that all of the altitudes written here, will be done using the book and tables of declension of Doctor Pero Nunez, so that the difference will come only from each person’s own judgment, or from the defects of the astrolabes; and so that this art discovered for the purpose of helping the navigators does not become discredited due to this diversity of altitudes, we should take into consideration how much we owe to it, for teaching
us how we should not ignore proximity to truth, how human the things are that men are able to understand. Because, as Monte Regio says in his triangles, of all good fortune it is better to know the approximate truth rather than to ignore completely that same truth, which one should not judge only by virtue of hitting the mark, but also by coming close to it.23
Here, again, should be noted the care Castro takes in always utiliz- ing the same solar tables, published by Pedro Nunes, so that the data could be better controlled, and the eventual differences attributed ex- clusively to defects in the instruments of measurement or to the error of the measurer. No less noteworthy is the consciousness he displays as regards the importance of describing in detail the process utilized in ob- taining the data—even assuming that this deviates from the “truth.” In addition, we must above all consider, yet again, his collaboration with the mathematician Pedro Nunes, the author of said tables.
At times, Castro gives up on finding explanations for certain phenom- ena or incidences, deeming that he does not possess any hypothesis for obtaining sufficient data to interpret them. With a light touch of humor he accepts this fact with resignation:
They may argue that we miscalculate the altitude of the sun; to this I respond, that it would be as strange for this to be a miscalculation, as for us to turn back around, having wind and prow to go forward, since five people calculated the altitude on this day, and all of us found ourselves in precise conformity with the sun. What this appears to me, is that we had a torrent of water that made us turn around, and if it was not this, may Apollo determine the cause.24
In still other cases, it seems to him rather that his question deserves to be studied by someone like Pedro Nunes, to whom he attributes a broader vision. For instance, after describing the steps he took in mak- ing his magnetic observations, which generated significant anomalies, he writes that, “the defect appears to be with the armillary sphere or demonstration, and because at present I cannot determine the cause, may the question be left to the doctor Pero Nunez.”25
Near the end of his Roteiro, Castro again observes an anomaly for which he has no explanation. Although accustomed to unanswered ques- tions, he reveals his intention to consult his teacher Pedro Nunes. Thus he concludes, “some aspect would mislead us that day, which we cannot ascertain, as befalls us in the majority of things and secrets of nature; but, however it may be, may the resolution of this question be left to the doctor pero nunez.”26
At times, certain discrepancies are attributed to the still-imperfect in- struments: “the armillary sphere is not suitably round, and the meridians prove poorly graduated, and the horizon does not move closely together
with the sphere, but all of these things are made poorly and imperfectly.” However, he adds that, “with all of these defects, much of the time [his findings] proved correct, as has been shown.”27
When practical reasons contrast with theoretical instructions received on land prior to departure, if these appear ill-advised, D. João de Castro does not hesitate to follow his own instincts. Still, he does not neglect to record the data from his measurements, as well as provide explanatory examples for those who may not understand him otherwise. He writes: