The Long View

March 21, 2007

The Beginnings of Western Science
The European Scientific Tradition in Philosophical, Religious, and Institutional Context: 600 BC to 1450 AD
David C. Lindberg (Chicago University Press, 1992)
473 pp. First reading.

As the title indicates, this book is a survey of the western scientific tradition from its origins until the early Renaissance, focusing on the disciplines of astronomy, mechanics, optics, and medicine. At each stage in the narrative, Lindberg’s intention is to put the scientific questions and practices into context, helping the reader to see why they asked the questions they did, and why they came to the conclusions they did.

The entire western scientific tradition is rooted in the Greek achievement. The Greeks themselves borrowed from the ancient Egyptians and Babylonians, but they greatly improved and expanded on those early foundations. They did fine work in astronomy, optics, and medicine, and founded a number of schools of natural philosophy.

When the Romans conquered the Greeks, they had the good sense to recognize the quality of their vanquished foes and absorbed into their own culture many of the Greek ideas. With the passing of time, however, there were few original Roman contributions to speculative science or natural philosophy, and gradually Roman discourse on science was reduced to a popular level, most of it read in Latin translations and popularizations. Knowledge of Greek was slowly eroded, and by the time of the Empire’s collapse there were few who could read Greek, and fewer still who understood the ancient Greek scientific texts. In a word, the Romans dropped the ball, and bequeathed to the early Middle Ages only a rudimentary scientific literature.

The Greek texts were not entirely lost, of course. Nestorian Christians, driven to the east, took many Greek books with them. They were conquered by the Islamic armies in the seventh century, and in the course of time the books were translated into Arabic. Greek natural philosophy seems to have made relatively little impact on Muslim thought, but Muslim scholars made a number of notable contributions to scientific knowledge. For instance, they invented the astrolabe for making precise astronomical measurements, developed the mathematics of trigonometry, and produced an impressive – and substantially correct – theory of vision.

In the twelfth century the slow Christian reconquest of Spain brought Western scholars into contact with their Islamic counterparts. The newly founded universities of Europe were hungry for new material, and a vigorous translation effort began. Year by year, European schools were flooded with new Latin translations of the ancient Greek texts, and they were taken up eagerly.

This story is, of course, well known (and I have written about it in more detail elsewhere). To some extent, that familiarity made this book a disappointment for me. I had been hoping for a detailed, technical discussion of the history of scientific ideas, and for the most part this book did not provide it.

On the other hand, a major merit of the book is the unwillingness of the author to sneer at the efforts of early natural philosophers. He sees, quite rightly, that if one views the problems they faced using the conceptual framework they possessed, they came consistently to reasonable conclusions. He is appreciative, for instance, of the work of the medieval alchemists, for he sees that their technical and procedural innovations stood ready to serve early modern chemistry when the theory of matter ripened. He is also alert to the fact that scientific breakthroughs often came from directions which surprise modern sensibilities. Most of pre-modern astronomy, for instance, was driven by astrological interests or religious (in the sense of calendrical) concerns.

One of my favourite instances of this unexpected cross-pollination concerns the origins of kinematic theory. In the twelfth century Peter Lombard wrote his famous Sentences, an enormous commentary on Scripture compiled from the writings of St. Augustine and other Church Fathers. The Sentences was structured as a series of ‘questions’, each of which addressed a particular point of doctrine or matter of dispute. The Sentences became a popular theology textbook at the medieval universities, and advanced students were required to write their own enormous commentary on it. Importantly, these commentaries tended to retain the division of the subject matter into ‘questions’, such that a scholar with an interest in a particular question could easily locate the pertinent section in each commentary. One of Lombard’s questions concerned the manner in which divine grace was increased in the soul; some held that the soul participates in grace without actually possessing or receiving the grace into itself, and that the degree of participation may wax or wane, which process we understand as increasing or decreasing grace ‘in’ the soul; others held that the soul could possess or receive into itself grace in greater or lesser quantity. As the commentaries on this question piled up, a quantitative theory of change was produced: rates of increase and decrease, for instance. All of this was in the context of what in Aristotelian natural philosophy was called motion of quality, grace being a quality of the soul that possesses it. But motion of quality was but one kind of motion enumerated in Aristotle’s Physics; another was motion of place. It was therefore a natural transition – natural to an Aristotelian physicist, that is – to apply a theory of change developed in a theological context to the motion of physical bodies. This is exactly what was done, at Oxford University, and from those efforts emerged the first definitions of velocity, instantaneous velocity, uniform and non-uniform motion, and even the mean speed theorem – all of which are basic to modern kinematic theory.

Lindberg’s discussion of early kinematics is one of the best sections of the book, since he does go into considerable detail. Two natural philosophers were especially important in developing the conceptual framework upon which the subject was built. John Buridan (c.1295-c.1358) was a priest, a student of William of Ockham, who worked at the University of Paris. In his efforts to understand the motion of bodies he developed the concept of impetus, obtained by combining the velocity of an object with its ‘quantity of matter’ (they had not yet arrived at the concept of mass). This concept of impetus bears a striking quantitative resemblance to our modern concept of momentum, yet it was conceptually quite different; impetus was conceived as being a property that causes motion, not just a quantity that describes it. Nevertheless Buridan’s ideas about impetus were a step toward the concept of inertia. He also voiced important clarifications about relative and absolute motion, and pointed out that astronomical models would be more economical if the earth, rather than the sphere of the fixed stars, rotated once per day. He argued, correctly, that the two scenarios would be observationally indistinguishable, but also concluded, incorrectly, that a rotating earth was impossible on the grounds that objects thrown directly upward would not fall at the same location. (This because he lacked the concept of inertia.)

Buridan’s general line of thought was taken up by a second fascinating figure, Nicole Oresme (c.1323-1382), also at the University of Paris. Oresme corrected Buridan’s error about falling bodies on a rotating earth, and did so using the analogy of a moving ship, very much as Galileo would do several hundred years later (and as physics classes do today). He also argued that Scriptural passages which seem to imply that the earth does not rotate could be understood as an instance of accommodation to our conventional manner of speaking of things. In fact, he refuted all of the objections to the idea that the earth rotates. Curiously, he nevertheless rejected the conclusion, interpreting the question as an illustration of the unreliability of natural reason (in the sense that it can seem to make plausible things which are false). He also took up the kinematic work of the Oxford philosophers, and developed a geometric method of representing kinematic quantities that bears a close resemblance to graph techniques. He showed, for instance, that the area under a velocity-time diagram is the distance travelled. Using his techniques, he was able to produce several geometric proofs, including one of the mean-speed theorem. Many of Oresme’s ideas seem very similar to those with which Galileo began his Discourse on Two New Sciences, and I am very curious to know whether Galileo was familiar with Oresme’s work.

Since I had never heard of either Buridan or Oresme before, it would certainly be too much to claim that I didn’t learn anything new from this book. There was also new material about early theories of vision, and of medical theory and practice, for instance, that I found fascinating, but most of this came in the final few chapters of the book. The earlier sections, which cover much the same ground as other histories of Western thought, were less rewarding for me. The book is very well written, with many explanatory diagrams, and, for someone new to the subject, would make an excellent introduction.

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