Thursday, September 16, 2010

Richard Carrier on Ancient Science

In chapter 15 of The Christian Delusion (Prometheus Books, 2010), Richard Carrier seeks to argue that pagan Greek science was about to achieve a scientific revolution when social collapse in the third century AD and the subsequent rise of the Christianity put a stop to it.

Although Richard refers to many modern scholars, none, as far as I am aware, would support his contention that Greek science was on the cusp of a revolution (say within a century or two of when the third century collapse curtailed progress). The scholar who comes closest to supporting Richard’s position is probably Lucio Russo in The Forgotten Revolution (Springer, 2003). Russo argues from a deep knowledge of the ancient sources that Greek science reached its peak in about 300BC. He suggests that this was the forgotten scientific revolution when the inverse square law of gravitation was discovered and that Aristarchus of Samos’s heliocentricism was more widespread than currently appreciated. For Russo, the early Roman Empire, the era of Ptolemy and Hero, was one of decadence and stagnation in Greek science.

Russo’s work has not carried the scholarly community with it. Richard himself also takes a very different view from Russo, arguing that the second century AD represented the pinnacle of Greek science. Ironically, Russo could almost be said to support Rodney Stark who claims that nothing much of significance happened in Greek science after the era of Aristotle (although Russo pushes the cut-off point forward by about fifty years).

So how far did Greek science get? I will concentrate my remarks on mechanics and physics, since these are the fields where most of my work on medieval science has been focused.

Richard notes that “Strato of Lampsacus extended… experimental method to machines and physics, by which time many of Aristotle’s physical theories had been altered or abandoned.” Strato was the second head of Aristotle’s Lyceum after the master himself. Little of his work survives, but in antiquity he had such a reputation for science that he was known as The Naturalist. His major achievement that we know of today was to show that air can be compressed from which he correctly deduced that it is made up of tiny particles floating in a vacuum. He also showed that a true vacuum can be created artificially. That’s impressive. But here is the rub. The passage of his work that states this is widely believed to have been incorporated into the introduction to Hero of Alexandria’s Pneumatics written in the first century AD, or three hundred years later. Richard says that “Hero had experimentally refuted Aristotle’s claim that a vacuum was impossible.” But if Hero has done these experiments himself, as Richard claims, why is he using a source that is three centuries old to prove it? OK, Strato was right. But this means that the theory Hero so successfully harnessed for his automata had been around for hundreds of years and had not been enhanced at all in the meantime.

Besides, although Strato had deduced an artificial vacuum is possible, he and all his successors assumed that suction, the basis of Hero’s pneumatic contrivances, is a result of nature abhorring the vacuum and attempting to fill it. And that’s false.
It gets worse for Hero, who represents, for Richard, the pinnacle of the Greek achievement in “mechanics, pneumatics and theatrical robotics”. In his Mechanics, Hero states unambiguously that heavy objects fall faster than light ones (and gives a reason why which looks like it might have come from Hipparchus (for whom see below), although it is hard to be sure). Now, this is a fundamental error that is easily proven wrong by the simplest of experiments. Yet Hero did not do this. He simply accepted the authority of Aristotle (and common sense) on the question. There is no evidence I know of that anyone did the simple experiment of dropping a heavy and light ball until John Philoponus in the sixth century AD, by which time Christians were supposedly letting science stagnate.

Hero also wrote about the law of reflection, correctly noting that the angles of incidence and reflection are the same. CB Boyer showed many years ago that this had been known since at least Aristotle’s day, so again Hero’s science is not new or the product of new experiments.

From the above, it would be fair to conclude that Hero was a practical mechanic and a tinker who pulled his theory from old books and never did anything approaching a true experiment in his life. The New Pauly, a scholarly encyclopaedia on classical studies, notes “Hero is not very original. His significance lies in the way that he summarises existing knowledge in the form of a handbook.” This is very different from the assessment of Hero implied by Richard in his chapter.

Getting back to Strato, we don’t know that he did any experiments in the field of mechanics. The only reference we have to his work in this subject is a discussion in Simplicius’s Commentary on the Physics of Aristotle from the sixth century AD. Strato observed that a flow of water breaks up as it falls which he interpreted as evidence, correctly, that falling objects accelerate. But Aristotle already knew as much. We must also rely on Simplicius for our knowledge of the mechanics of Hipparchus. Now he was certainly an excellent astronomer. Richard also notes that Hipparchus worked on increasingly-correct theories of projectile motion. But this is a bit of a stretch. Hipparchus’s one good idea of projected force would later be picked up by John Philoponus and reappear in the High Middle Ages in a more developed form as impetus. But we see no progress in the field of projectile motion between Hipparchus and Philoponus.

Overall, I am not convinced by Richard’s argument that Greece was on the point of a scientific revolution when the third century collapse cut off progress. Indeed, I find myself in closer agreement with Russo that the golden age of Greek science was around 300BC. So, in my opinion, Richard’s second argument against the Holy Science thesis is lacking, even though the first one succeeds. Of course, he may have uncovered new evidence in the course of his research and we will need to await its publication to be sure.

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Crude said...

I apologize for posting an off-topic comment, but I was hoping the esteemed historians on this blog could help me with a simple question. Relevant to this topic, in fact.

There's that famous exchange between Laplace and Napoleon, where Napoleon is presented with Laplace's work, Napoleon notes the lack of mention of God, and Laplace responds with "I have no need of that hypothesis."

Here's the problem. If I recall correctly, there's more to that exchange. I know that Napoleon says something like "Oh, but it is a great hypothesis, isn't it? It explains many things." But on the, in my estimation, fifty zillion sites on google that quote this exchange, that's where they leave off.

If memory serves me, there is something Laplace says in reply to Napoleon at that point. Would any of you know it? And particularly know the source?

Thank you.

Alice C. Linsley said...

The notion that the Earth revolves around the Sun was first proposed by ancient Egyptian priests about 3000 years ago, NOT by Aristarchus of Samos in the 3rd c. B.C. The Sun, as the emblem of the Creator, was conceived cosmologically as being at the sacred center.

Eupolemus in Eusebius ascribed the origin of astronomy to Nok (Enoch) of west central Africa. Kain and Set married daughters of Nok.

Andrew Brew said...

According to this account:
the second remark was not made by Napoleon at all, so perhaps that is why the conversation is not continued in most accounts. Ah, I see the same is quoted by Wikipedia, so not very obscure.

The exchange usually seems to be quoted to hint that leaving God out of scientific formulations was a novelty in the early nineteenth century. A very strange notion, as readers of this blog will know.

Manual labor said...

Wasn't the fall of the western portion of the roman empire beginning around the start of the 4th century? It wasn't sacked until the mid or late 5th century until Alaric and the Visigoths came.