"God's Philosophers" by James Hannam

The Scotsman says this book "makes enjoyable reading out of some seriously dusty history". Yes! The reading is wonderfully enjoyable but No! the history is not in the least bit dusty.

Hannam's thesis is that the philosophers of the misnamed "dark" ages laid the foundations for modern science. Contrary to received opinion the church did not repress their ideas. On the contrary, by an early decision that natural philosophers should not stray into theology the church protected natural philosophers. The monasteries and universities (sponsored mainly by the church) were fertile grounds for new ideas to breed. Although the official philosophy was Aristotle's, and this was such an integrated system that it was difficult to create an alternative because all parts had to be replaced, the natural philosophers were free to chip away at Aristotelian beliefs. This was difficult because, at least in mechanics, Aristotle's ideas are intuitive and seem to conform to observation. Until a society has the resources and technology to make systematic detailed observations it cannot really progress beyond everyday beliefs. Thus the Earth seems not to move and if it did move one should be able to observe parallax effects with the stars. But the stars are so far away that you can't observe parallax without a telescope and therefore the Earth does not move.

Despite these handicaps the mediaeval philosophers made substantial progress chipping away at the corners of Aristotelianism and developing new logical and mathematical tools.  Progress was further slowed until the printing press was invented. Shortly after that the fashion for humanism (clearly the boo-hiss villain in Hannam's eyes) meant that Aristotle was valued far beyond the mediaeval ideas purely because it was older. But the new scientists Galileo and Kepler owed a tremendous (often unacknowledged) debt to mediaeval philosophers many of whose ideas they quoted verbatim and unattributed.

Wonderful things I learned from this book:

• Aristotle considered that all things eg sheep have two categories of properties:
• substance: those properties without which they cannot be sheep (eg being an animal)
• accident: those properties which are not essential (such as whiteness)
• Archbishop Lanfranc (yes, that one, Anselm's teacher too!) used these properties to explain how the bread and wine could become Christ's body and blood in the mass despite appearing to still be bread and wine. He said the accidental properties were retained but the substantial ones altered; hence transubstantiation!
• Philosophers who believed that the concept sheep can exist independently are realists. Those who believe that  categorical concepts have no separate reality but that there are only lots and lots of individual sheep are called nominalists. William of Ockham used his razor to suggest that adding concepts was wrong, hence he was a nominalist. Science is impossible if you can't believe in concepts such as the Law of Gravity; scientists are relaists. Ockham's razor has been much misused to cut in a completely different way from that intended.
• Throughout the middle ages everyone knew that parts of the Bible were not to be taken literally. Despite the Bible suggesting that the Moon produces its own illumination Pope Innocent III (died 1216) knew it shone by reflected light.
• There was loads of scepticism about both alchemy and astrology for the simple reason that they did not appear to work. Nevertheless, both acids and alcohol were isolated by Christian mediaeval scientists in the thirteenth century and misattributed to earlier Arabic scientists.
• Thomas Bradwardine (c1290-1349), one of the 'Mertonian Calculators' used proto logarithms in his study of motion 250 years before they were 'invented' by Napier.
• Jean Buridan developed the idea of impetus. With the Mertonian analyses he more or less solved the problems of motion before 1360, at least 200 years before Galileo.
• Albert of Saxony (c1316-1390) drew the first picture of a curved trajectory, even though it is straight in its first part.
• Eratosthenes calculated the Earth's circumference to be between 24,000 and 30,000 miles (it is actually 24,900). This was known through Pliny the Elder's work. Ptolemy miscalculated it to be between 17,000 and 22,000 miles. Ptolemy, translated in 1406, became popular so Columbus used it to 'lose' 10,000 miles from his sea trip from Spain to the Indies.
• Paper was affordable compared to parchment. The first recorded paper mill in Italy was 1276 and France in 1348.
• Printing had the edge in the West because, unlike China and Japan, we have an alphabet which means it is far quicker to typeset a page.
• The mediaeval people invented spectacles, the mechanical clock, the blast furnace and the windmill all by themselves.

Two very minor criticisms. First there is a feel that the book is one long list of very short potted biographies of some very interesting people. Second, I was disappointed that more was not made of the inventions.

This was a wonderful book.

July 2011; 342 pages