85 - Sky Writing: Astronomy, Astrology, and Philosophy

Posted on 17 June 2012

Ptolemy uses philosophy in the service of studying the stars, while philosophers of all persuasions evaluate the widespread practice of astrology.


Further Reading

• P. Adamson, “Plotinus on Astrology,” Oxford Studies in Ancient Philosophy 35 (2008), 265-91.

• L. Bouché-Leclercq, L’astrologie grecque (Paris: 1899).

• T. Barton, Ancient Astrology (London: Routledge, 1994).

• A.A. Long, “Astrology: Arguments Pro and Contra,” in Science and Speculation: Studies in Hellenistic Theory and Practice, ed. J. Barnes et al (Cambridge: 1982), 165-92.

• O. Neugebauer, Astronomy and History: Selected Essays (New York: Springer-Verlag, 1983).


tommm 25 September 2012

Thinking about Astrology (now a modern example of sloppy thinking) makes me wonder if there is something that changed as philosophy moved from Greece to Rome. We are often told about ancient Greek scientific and mathematical discoveries, but I don't think of Rome as making many theoretical advances along these lines. Is this reflected in philosophy of Roman times? Was there something in Roman thinking that prevented an Eratosthenes or Archimedes? Thanks!

Hi there,

I seem to recall that we touched on this in the Cuomo interview so you might take a listen to that; but basically I think the answer is that the Romans liked to think of themselves as more "practical" than the airy fairy Greeks, and excelled in things like engineering and architecture, but in this sphere at least they were really innovative, think for instance of Vitruvius. (There was a good episode of In Our Time about him last year.) 



Nidhi Shrimali 12 March 2019

According to Pandit NM Shrimali’s astrology, Sonela stone is related to Ratna Guru and it has authority over Sagittarius and Pisces. According to Western astrology, it is the Bird Stone of Sagittarius zodiac. This is the Top Ratna of Pukhraj. Therefore, wearing it gives better GURU related benefits, honor is attained, decision-making ability develops an interest in social work increases. By wearing this precious stone, all gains related to the guru are obtained. It is helpful in increasing wealth and respect. This means that wearing sonela increases the chances of getting economic benefits.

Elliot 20 June 2019

Hi Peter,

I have a pressing objection to Stoic interpretations of astrology which I cannot help but think undermines the consistency of the former’s beliefs. As we know, Stoic determinist doctrine insists that every future event is premeditated and unchangeable. On the surface, astrology could appear to be a very beneficial utility to them to help advance their views, as you mentioned on the show. But there is one big problem. Obviously, astrological predictions can’t be correct ALL the time, as astrologers have always told some fortunes that fail to ever come true. To the Stoics, I see only one way of explaining this. To rationalize astrological imperfection, the Stoics would have to admit that it is FATED for the horoscopes to sometimes be incorrect. But if this is the case, then there will be no way of knowing which astrology predictions are to be taken seriously, and which ones are not. Hence, as a Stoic, it would appear that astrology would be not only completely useless, but a vehement opponent in the struggle for dominance over destiny-based philosophy. A Stoic would have to consider it illegitimate because it is not always accurate. This would be particularly true because astrology most often deals with predicting events that are not “up to us.” Has anyone addressed this concern, and if so, what was their response? Thanks! 



I don't know of an ancient source that sets out your objection as such, but to be honest I think the Stoics can answer this pretty easily. Consider the following analogy: weather prediction shows that there are causal patterns that result in certain weather conditions. This is why forecasters can look at the present and see the future. Even though they get it wrong some of the time, the fact that they often or even usually get it right shows they are grasping a set of genuinely causal relations. Similarly, astrologers get things right most of the time, we are assuming, which they would not be able to do just by luck (you and I know it was luck, but we have different beliefs about their success rate than ancient people generally did - back then it was seen as fairly reliable, as we see weather forecasting today). The fact that they get things wrong, as with the weather forecasters, is just a sign that the science is not perfect, but the fact that they get things right so much shows that the science reveals something true about the world. As for why they would be fated to make mistakes, clearly humans are fated to make mistakes of all sorts, all the time, so astrology is not a special case here (and the Stoics have things to say in explanation: it's all for the best, we may not be able to say how, etc etc). Does that persuade you?

Yes, that makes perfect sense. So essentially, because the Stoic material world is perfect and unchangeable in ways that are far beyond the conception of the mortal man, it is not the art of astrology which is flawed, but the human observer! Certainly, by this metric, the Cosmos would never deliberately supply us with false information about the future, we are just incapable of fully comprehending its many intricacies. Although, if the astrologers adhered to this doctrine and wanted to strive towards becoming Sages, they would suspend judgement about their observations unless they knew for sure that what they were reading was accurate, which certainly cannot be done. So I suppose astrologers could not have been perfect Stoics, but perfect Stoics who were not astrologers could still find something to admire in astrology. 

Yes, that's a good point: a Stoic sage astrologer would probably withhold assent from her predictions, but as we know Stoics suggested that the sage can act on probabilities and not only on total certainties. (Pretty hard to act otherwise.) In fact ancient astrologers often emphasized the probabilistic nature of their discipline, so this would fit very well with the scientific status claimed by the adherents of the art at that time. The same would go for other disciplines where certain outcomes are hard or impossible to get, like medicine. 

Victor Hugo F Santos 15 January 2020

Hi Peter, 

I believe that episode corrupt, because I can't hear the audio here or in spotify. 


Peter Adamson 15 January 2020

In reply to by Victor Hugo F Santos

Hi, can you re-check and see if it works now? I just tried to stream it here on this page and it worked ok. So may be a problem at your end or it was a temporary glitch perhaps.

Daniel Gamermann 23 June 2020

In reply to by Peter Adamson

I have been having problems trying to listen to this episode. I usually use castbox to download my podcasts, and this one is the only one I have been unable to get there. Today I came here in the website to try and donwload it, but It is not working either: the download never starts until the connection timesout. 

In any case the HoP is great, keep the good work and, if possible, please fix this episode or make it available from somewhere else.


Peter Adamson 24 June 2020

In reply to by Daniel Gamermann

Hm, that's strange. It streams for me ok now, so maybe you could try again? We have in the past had a problem where episodes were temporarily unavailable but then it fixed itself. Please let me know if you still have trouble with it, and thanks for listening!

Daniel Gamermann 24 June 2020

In reply to by Peter Adamson


Thanks for the reply.
No, there is no luck, still doesnt work. Actually, it has been a long long time since I've tried to download it for the first time in castbox, but only yesterday I had the idea to try here in the webpage and it does not work either. It is funny because this is the only episode so far I have experienced any problem...
Anyway, thanks!

Peter Adamson 25 June 2020

In reply to by Daniel Gamermann

That's strange, since it does work for me at this end. If all else fails you should also be able to get it off iTunes (I think even without registering with Apple you can just go to the website). The podcast is also on Spotify, you could try that too.

Phil Gyford 21 March 2022

In reply to by Peter Adamson

There’s still something not quite right, and yet it is possible to download.

I tried playing from this page and nothing happened the first couple of times. I tried other pages and their files played fine. I came back here, and this time it played.

I’d tried here because, attempting to download the file using the Overcast app, I kept getting an error message about an invalid or corrupt (I forget which) file. I tried several times, and always the same. After my eventual success with this page I figured it must be an intermittent error - a bad file cached somewhere? - so I persisted with Overcast and eventually it managed to download the file!

So, if anyone has a problem downloading this particular file, I can only suggest persistence.

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