To Explain the World: The Discovery of Modern Science (8 page)

It is not that there was no theory behind the practice of medicine. There was humorism, the theory of the four humors—blood, phlegm, black bile, and yellow bile, which (respectively) make us sanguine, phlegmatic, melancholy, or choleric. Humorism was introduced in classical Greek times by Hippocrates, or by colleagues of his whose writings were ascribed to him. As briefly stated much later by John Donne in “The Good Morrow,” the theory held that “whatever dies was not mixed equally.” The theory of humorism was adopted in Roman times by Galen of Pergamon, whose writings became enormously influential among the Arabs and then in Europe after about AD 1000. I am not aware of any effort while humorism was generally accepted ever to test its effectiveness experimentally. (Humorism survives today in Ayurveda, traditional Indian medicine, but with just three humors: phlegm, bile, and wind.)

In addition to humorism, physicians in Europe until modern times were expected to understand another theory with supposed medical applications: astrology. Ironically, the opportunity for physicians to study these theories at universities gave medical doctors much higher prestige than surgeons, who knew how to do really useful things like setting broken bones but until modern times were not usually trained in universities.

So why did the doctrines and practices of medicine continue
so long without correction by empirical science? Of course, progress is harder in biology than in astronomy. As we will discuss in
Chapter 8
, the apparent motions of the Sun, Moon, and planets are so regular that it was not difficult to see that an early theory was not working very well; and this perception led, after a few centuries, to a better theory. But if a patient dies despite the best efforts of a learned physician, who can say what is the cause? Perhaps the patient waited too long to see the doctor. Perhaps he did not follow the doctor’s orders with sufficient care.

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 Greenblatt
⁶
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.