At least humorism and astrology had an air of being scientific. What was the alternative? Going back to sacrificing animals to Aesculapius?
Another factor may have been the extreme importance to patients of recovery from illness. This gave physicians authority over them, an authority that physicians had to maintain in order to impose their supposed remedies. It is not only in medicine that persons in authority will resist any investigation that might reduce their authority.
5
Ancient Science and Religion
The pre-Socratic Greeks took a great step toward modern science when they began to seek explanations of natural phenomena without reference to religion. This break with the past was at best tentative and incomplete. As we saw in Chapter 1, Diogenes Laertius described the doctrine of Thales as not only that “water is the universal primary substance,” but also that “the world is animate and full of divinities.” Still, if only in the teachings of Leucippus and Democritus, a beginning had been made. Nowhere in their surviving writings on the nature of matter is there any mention of the gods.
It was essential for the discovery of science that religious ideas be divorced from the study of nature. This divorce took many centuries, not being largely complete in physical science until the eighteenth century, nor in biology even then.
It is not that the modern scientist makes a decision from the start that there are no supernatural persons. That happens to be my view, but there are good scientists who are seriously religious. Rather, the idea is to see how far one can go without supposing supernatural intervention. Only in this way can we do science, because once one invokes the supernatural, anything can be explained, and no explanation can be verified. This is why the “intelligent design” ideology being promoted today is not science—it is rather the abdication of science.
Plato’s speculations were suffused with religion. In Timaeus he described how a god placed the planets in their orbits, and he may have thought that the planets were deities themselves. Even when Hellenic philosophers dispensed with the gods, some of them described nature in terms of human values and emotions, which generally interested them more than the inanimate world. As we have seen, in discussing changes in matter, Anaximander spoke of justice, and Empedocles of strife. Plato thought that the elements and other aspects of nature were worth studying not for their own sake, but because for him they exemplified a kind of goodness, present in the natural world as well as in human affairs. His religion was informed by this sense, as shown by a passage from the Timaeus: “For God desired that, so far as possible, all things should be good and nothing evil; wherefore, when He took over all that was visible, seeing that it was not in a state of rest but in a state of discordant and disorderly motion, He brought it into order out of disorder, deeming that the former state was in all ways better than the latter.”1
Today, we continue to seek order in nature, but we do not think it is an order rooted in human values. Not everyone has been happy about this. The great twentieth-century physicist Erwin Schrödinger argued for a return to the example of antiquity,2 with its fusion of science and human values. In the same spirit, the historian Alexandre Koyré considered the present divorce of science and what we now call philosophy “disastrous.”3 My own view is that this yearning for a holistic approach to nature is precisely what scientists have had to outgrow. We simply do not find anything in the laws of nature that in any way corresponds to ideas of goodness, justice, love, or strife, and we cannot rely on philosophy as a reliable guide to scientific explanation.
It is not easy to understand in just what sense the pagans actually believed in their own religion. Those Greeks who had traveled or read widely knew that a great variety of gods and goddesses were worshipped in the countries of Europe, Asia, and Africa. Some of the Greeks tried to see these as the same deities under different names. For instance, the pious historian Herodotus reported, not that the native Egyptians worshipped a goddess named Bubastus who resembled the Greek goddess Artemis, but rather that they worshipped Artemis under the name of Bubastus. Others supposed that these deities were all different and all real, and even included foreign gods in their own worship. Some of the Olympian gods, such as Dionysus and Aphrodite, were imports from Asia.
Among other Greeks, however, the multiplicity of gods and goddesses promoted disbelief. The pre-Socratic Xenophanes famously commented, “Ethiopians have gods with snub noses and black hair, Thracians gods with gray eyes and red hair,” and remarked, “But if oxen (and horses) and lions had hands or could draw with hands and create works of art like those made by men, horses would draw pictures of gods like horses, and oxen of gods like oxen, and they would make the bodies [of their gods] in accordance with the form that each species itself possesses.”4 In contrast to Herodotus, the historian Thucydides showed no signs of religious belief. He criticized the Athenian general Nicias for a disastrous decision to suspend an evacuation of his troops from the campaign against Syracuse because of a lunar eclipse. Thucydides explained that Nicias was “over-inclined to divination and such things.”5
Skepticism became especially common among Greeks who concerned themselves with understanding nature. As we have seen, the speculations of Democritus about atoms were entirely naturalistic. The ideas of Democritus were adopted as an antidote to religion, first by Epicurus of Samos, who settled in Athens and at the beginning of the Hellenistic era founded the Athenian school known as the Garden. Epicurus in turn inspired the Roman poet Lucretius. Lucretius’ poem On the Nature of Things moldered in monastic libraries until its rediscovery in 1417, after which it had a large influence in Renaissance Europe. Stephen Greenblatt6 has traced the impact of Lucretius on Machiavelli, More, Shakespeare, Montaigne, Gassendi,* Newton, and Jefferson. Even where paganism was not abandoned, there was a growing tendency among the Greeks to take it allegorically, as a clue to hidden truths. As Gibbon said, “The extravagance of the Grecian mythology proclaimed, with a clear and audible voice, that the pious inquirer, instead of being scandalized or satisfied with the literal sense, should diligently explore the occult wisdom, which had been disguised, by the prudence of antiquity, under the mask of folly and of fable.”7 The search for hidden wisdom led in Roman times to the emergence of the school known to moderns as Neoplatonism, founded in the third century AD by Plotinus and his student Porphyry. Though not scientifically creative, the Neoplatonists retained Plato’s regard for mathematics; for instance, Porphyry wrote a life of Pythagoras and a commentary on Euclid’s Elements. Looking for hidden meanings beneath surface appearances is a large part of the task of science, so it is not surprising that the Neoplatonists maintained at least an interest in scientific matters.
Pagans were not much concerned to police each other’s private beliefs. There were no authoritative written sources of pagan religious doctrine analogous to the Bible or the Koran. The Iliad and Odyssey and Hesiod’s Theogony were understood as literature, not theology. Paganism had plenty of poets and priests, but it had no theologians. Still, open expressions of atheism were dangerous. At least in Athens an accusation of atheism was occasionally used as a weapon in political debate, and philosophers who expressed disbelief in the pagan pantheon could feel the wrath of the state. The pre-Socratic philosopher Anaxagoras was forced to flee Athens for teaching that the Sun is not a god but a hot stone, larger than the Peloponnesus.
Plato in particular was anxious to preserve the role of religion in the study of nature. He was so appalled by the nontheistic teaching of Democritus that he decreed in Book 10 of the Laws that in his ideal society anyone who denied that the gods were real and that they intervened in human affairs would be condemned to five years of solitary confinement, with death to follow if the prisoner did not repent.
In this as in much else, the spirit of Alexandria was different from that of Athens. I do not know of any Hellenistic scientists whose writings expressed any interest in religion, nor do I know of any who suffered for their disbelief.
Religious persecution
was not unknown under the Roman Empire. Not that there was any objection to foreign gods. The pantheon of the later Roman Empire expanded to include the Phrygian Cybele, the Egyptian Isis, and the Persian Mithras. But whatever else one believed, it was necessary as a pledge of loyalty to the state also to publicly honor the official Roman religion. According to Gibbon, the religions of the Roman Empire “were all considered by the people, as equally true, by the philosopher, as equally false, and by the magistrate, as equally useful.”8 Christians were persecuted not because they believed in Jehovah or Jesus, but because they publicly denied the Roman religion; they would generally be exonerated if they put a pinch of incense on the altar of the Roman gods.
None of this led to interference with the work of Greek scientists under the empire. Hipparchus and Ptolemy were never persecuted for their nontheistic theories of the planets. The pious pagan emperor Julian criticized the followers of Epicurus, but did nothing to persecute them.
Though illegal because of its rejection of the state religion, Christianity spread widely through the empire in the second and third centuries. It was made legal in the year 313 by Constantine I, and was made the sole legal religion of the empire by Theodosius I in 380. During those years, the great achievements of Greek science were coming to an end. This has naturally led historians to ask whether the rise of Christianity had something to do with the decline of original work in science.
In the past attention centered on possible conflicts between the teachings of religion and the discoveries of science. For instance, Copernicus dedicated his masterpiece On the Revolutions of the Heavenly Bodies to Pope Paul III, and in the dedication warned against using passages of Scripture to contradict the work of science. He cited as a horrible example the views of Lactantius, the Christian tutor of Constantine’s eldest son:
But if perchance there are certain “idle talkers” who take it on themselves to pronounce judgment, though wholly ignorant of mathematics, and if by shamelessly distorting the sense of some passage in Holy Writ to suit their purpose, they dare to reprehend and to attack my work; they worry me so little that I shall even scorn their judgments as foolhardy. For it is not unknown that Lactantius, otherwise a distinguished writer but hardly a mathematician, speaks in an utterly childish fashion concerning the shape of the Earth, when he laughs at those who said that the Earth has the form of a globe.9
This was not quite fair. Lactantius did say that it was impossible for sky to be under the Earth.10 He argued that if the world were a sphere then there would have to be people and animals living at the antipodes. This is absurd; there is no reason why people and animals would have to inhabit every part of a spherical Earth. And what would be wrong if there were people and animals at the antipodes? Lactantius suggests that they would tumble into “the bottom part of the sky.” He then acknowledges the contrary view of Aristotle (not quoting him by name) that “it is the nature of things for weight to be drawn to the center,” only to accuse those who hold this view of “defending nonsense with nonsense.” Of course it is Lactantius who was guilty of nonsense, but contrary to what Copernicus suggested, Lactantius was relying not on Scripture, but only on some extremely shallow reasoning about natural phenomena. All in all, I don’t think that the direct conflict between Scripture and scientific knowledge was an important source of tension between Christianity and science.
Much more important, it seems to me, was the widespread view among the early Christians that pagan science is a distraction from the things of the spirit that ought to concern us. This goes back to the very beginnings of Christianity, to Saint Paul, who warned: “Beware lest any man spoil you through philosophy and vain deceit, after the tradition of men, after the rudiments of the world, and not after Christ.”11 The most famous statement along these lines is due to the church father Tertullian, who around the year 200 asked, “What does Athens have to do with Jerusalem, or the Academy with the Church?” (Tertullian chose Athens and the Academy to symbolize Hellenic philosophy, with which he presumably was more familiar than he was with the science of Alexandria.) We find a sense of disillusion with pagan learning in the most important of the church fathers, Augustine of Hippo. Augustine studied Greek philosophy when young (though only in Latin translations) and boasted of his grasp of Aristotle, but he later asked, “And what did it profit me that I could read and understand all the books I could get in the so-called ‘liberal arts,’ when I was actually a slave of wicked lust?”12 Augustine was also concerned with conflicts between Christianity and pagan philosophy. Toward the end of his life, in 426, he looked back at his past writing, and commented, “I have been rightly displeased, too, with the praise with which I extolled Plato or the Platonists or the Academic philosophers beyond what was proper for such irreligious men, especially those against whose great errors Christian teaching must be defended.”13
Another factor: Christianity offered opportunities for advancement in the church to intelligent young men, some of whom might otherwise have become mathematicians or scientists. Bishops and presbyters were generally exempt from the jurisdiction of the ordinary civil courts, and from taxation. A bishop such as Cyril of Alexandria or Ambrose of Milan could exercise considerable political power, much more than a scholar at the Museum in Alexandria or the Academy in Athens. This was something new. Under paganism religious offices had gone to men of wealth or political power, rather than wealth and power going to men of religion. For instance, Julius Caesar and his successors won the office of supreme pontiff, not as a recognition of piety or learning, but as a consequence of their political power.
Greek science survived for a while after the adoption of Christianity, though mostly in the form of commentaries on earlier work. The philosopher Proclus, working in the fifth century at the Neoplatonic successor to Plato’s Academy in Athens, wrote a commentary on Euclid’s Elements, with some original contributions. In Chapter 8 I will have occasion to quote a later member of the Academy, Simplicius, for his remarks, in a commentary on Aristotle, about Plato’s views on planetary orbits. In the late 300s there was Theon of Alexandria, who wrote a commentary on Ptolemy’s great work of astronomy, the Almagest, and prepared an improved edition of Euclid. His famous daughter Hypatia became head of the city’s Neoplatonic school. A century later in Alexandria the Christian John of Philoponus wrote commentaries on Aristotle, in which he took issue with Aristotle’s doctrines concerning motion. John argued that the reason bodies thrown upward do not immediately fall down is not that they are carried by the air, as Aristotle had thought, but rather that when they are thrown bodies are given some quality that keeps them moving, an anticipation of later ideas of impetus or momentum. But there were no more creative scientists or mathematicians of the caliber of Eudoxus, Aristarchus, Hipparchus, Euclid, Eratosthenes, Archimedes, Apollonius, Hero, or Ptolemy.
Whether or not because of the rise of Christianity, soon even the commentators disappeared. Hypatia was killed in 415 by a mob, egged on by Bishop Cyril of Alexandria, though it is difficult to say whether this was for religious or political reasons. In 529 the emperor Justinian (who presided over the reconquest of Italy and Africa, the codification of Roman law, and the building of the great church of Santa Sophia in Constantinople) ordered the closing of the Neoplatonic Academy of Athens. On this event, though Gibbon is predisposed against Christianity, he is too eloquent not to be quoted:
The Gothic arms were less fatal to the schools of Athens than the establishment of a new religion, whose ministers superseded the exercise of reason, resolved every question by an article of faith, and condemned the infidel or skeptic to eternal flames. In many a volume of laborious controversy they espoused the weakness of the understanding and the corruption of the heart, insulted human nature in the sages of antiquity, and proscribed the spirit of philosophical inquiry, so repugnant to the doctrine, or at least to the temper, of a humble believer.14
The Greek half of the Roman Empire survived until AD 1453, but as we shall see in Chapter 9, long before then the
vital center of scientific research had moved east, to Baghdad.
PART II
GREEK ASTRONOMY
The science that in the ancient world saw the greatest progress was astronomy. One reason is that astronomical phenomena are simpler than those on the Earth’s surface. Though the ancients did not know it, then as now the Earth and the other planets moved around the Sun on nearly circular orbits, at nearly constant velocities, under the influence of a single force—gravitation—and they spun on their axes at essentially constant rates. The same applied to the Moon in its motion around the Earth. In consequence the Sun, Moon, and planets appeared from Earth to move in a regular and predictable way that could be and was studied with considerable precision.
The other special feature of ancient astronomy is that it was useful, in a way that ancient physics generally was not. The uses of astronomy are discussed in Chapter 6.
Chapter 7 discusses what, flawed as it was, can be considered a triumph of Hellenistic science: the measurement of the sizes of the Sun, Moon, and Earth, and the distances to the Sun and Moon. Chapter 8 treats the problem posed by the apparent motion of the planets, a problem that continued to concern astronomers through the Middle Ages, and that eventually led to the birth of modern science.
6
The Uses of Astronomy1
Even before the start of history, the sky must have been commonly used as a compass, a clock, and a calendar. It could not have been difficult to notice that the Sun rises every morning in more or less the same direction, that during the day one can tell how much time there is before night from the height of the Sun in the sky, and that hot weather will follow the time of year when the day lasts longest.
We know that the stars were used for similar purposes very early in history. Around 3000 BC the Egyptians knew that the crucial event in their agriculture, the flooding of the Nile in June, coincided with the heliacal rising of the star Sirius. (This is the day in the year when Sirius first becomes visible just before dawn; earlier in the year it is not visible at night, and later it is visible well before dawn.) Homer, writing before 700 BC, compares Achilles to Sirius, which is high in the sky at the end of summer: “that star, which comes on in the autumn and whose conspicuous brightness far outshines the stars that are numbered in the night’s darkening, the star they give the name of Orion’s Dog, which is brightest among the stars, and yet is wrought as a sign of evil and brings on the great fever for unfortunate mortals.”2 A little later, the poet Hesiod in Works and Days told farmers that grapes are best cut at the heliacal rising of Arcturus, and that plowing should be done at the cosmical setting of the Pleiades constellation. (This is the day in the year when these stars first are seen to set just before sunrise; earlier in the year they do not set at all before the Sun comes up, and later they set well before dawn.) Following Hesiod, calendars known as paramegmata, which gave the risings and settings of conspicuous stars for each day, became widely used by Greeks whose city-states had no other shared way of identifying dates.
To Explain the World: The Discovery of Modern Science Page 6
