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Cicero and Pico vs Ptolemy
Two famous attacks on astrology 50 BC and 1490 AD

Abstract -- The validity of astrology and divination has been disputed throughout the ages, most famously by Cicero (106-43 BC) and Pico della Mirandola (1463-1494). Here their arguments are summarised along with a supposed refutation by Ptolemy. Their arguments remain largely as valid today as they were then.

Coicero's famous De Divinatione
Cicero (106-43 BC) is recognised as the greatest Roman writer of his time. He wrote many famous speeches, letters, and works of philosophy that would influence the style of speakers and writers everywhere. He was equally at home with Greek and Latin, and was possibly the most cultured man that Rome had produced (Breasted, A Brief History of Ancient Times revised edition 1936:305).

Cicero's De Divinatione (On Divination) incorporates earlier Greek arguments now lost. It is one of the more famous attacks on divination, part of which includes astrology. It takes the form of a dialogue between himself and his brother Quintus. Quintus presents arguments in favour of divination, which Cicero then demolishes with merciless logic.

Interestingly, Cicero is arguing as an insider, because he was also an augur (official interpreter) of bird behaviour. He denies any conflict of interest, because augury was little used in Rome, and even then only to control the public's "excesses", presumably by manipulating the outcomes. More importantly, he saw a soothsayer as a wise counsellor - what mattered was not the soothsaying but the wisdom.

The folklorist Lewis Spence comments "The tenets of the Roman augurs were that for signs of the gods one must look towards the sky ... He carefully observed every sign ... such as lightning, the appearance of birds, and so forth. ... The reading of omens was also effected by the feeding of birds and observing the manner in which they ate" (Encyclopaedia of Occultism 1920:126).

All of the quotes that follow are from the English translation by WA Falconer (Cicero: De Senectute, De Amicitia, De Divinatione 1938):

Cicero's arguments against astrology
Cicero begins by noting that divination exists everywhere. "A really splendid and helpful thing it is - if only such a faculty exists - since by its means men may approach very near to the power of gods". But it has no place in cases where the senses "are sufficient in themselves and require no aid from divination", which include science, art, philosophy and politics. "And since it is of no use in these cases there is no use for it anywhere". It cannot foretell things that happen by chance, because such things by definition cannot be foretold, and if they could they would not be chance. Even if divination could tell the future, the disadvantages would outweigh the advantages, for example it would allow a person "to peer into every man's house to see what he needs" (p.489).

Cicero then looks at each kind of divination and argues that each is preposterous. His description of the things that contradict the claims of astrologers takes up about 9% of De Divinatione. His main arguments against astrology still apply today:

(1) Given their "almost limitless distances, what influence can the planets exercise?"

(2) Weather has a big effect on man but is ignored by astrologers, who consider only "some subtle, imperceptible, well-nigh inconceivable force which is due to the condition of the sky".

(3) It is clear that "the carriage and gestures of children are derived from their parents", which would not be the case if they were derived from the sky's condition.

(4) As for time twins: "the fact that men who were born at the very same instant, are unlike in character, career, and in destiny, makes it very clear that the time of birth has nothing to do in determining man's course in life".

(5) From the many striking differences between Indians and Persians: "it is evident that one's birth is more affected by local environment than by the condition of the moon".

(6) In 216 BC, at Cannae in south eastern Italy, Hannibal had massacred an army of 70,000 Romans. Every family in Rome was in mourning. "Did all the Romans who fell at Cannae have the same horoscope? Yet all had one and the same end".

(7) "Were all the men eminent for intellect and genius born under the same star? Was there ever a day when countless numbers were not born? And yet there never was another Homer. ... What stupendous power delusion has!" He concludes: "why say more against a theory which every day's experience refutes?" (pp.469-483).

Cicero's attack on astrology did not go unnoticed:

A refutation of Cicero by Ptolemy
Ptolemy's Tetrabiblos c.150 AD, in what US astrologer and classicist George Noonan calls "the most brilliant defense of astrology ever written" (Classical Scientific Astrology 1984:8), refutes Cicero by arguing (and here we paraphrase):

If a man should accurately observe the effects of sun and moon, such as heating and moistening, what is to stop him predicting their influence at any time, and thus predicting for a concurrent birth the temperament attuned to that influence? (Book 1 Chapter 2).

This is the kind of causal astrology which Noonan hoped would become "a recognized scientific discipline" (p.22). Against this the classicist AA Long comments:

"Seldom, one could say from our own perspective, have knowledge, intelligence and rhetorical skill been more misused than in the opening three chapters of Ptolemy's Tetrabiblos [which argue why astrology is valid and beneficial]. Yes, we must grant Ptolemy the obvious empirical power of the sun, but after that it is all 'rhetoric and dialectic' [ie arguments and studied vagueness as in the above paraphrase instead of direct evidence]" (in Barnes et al, Science and Speculation: Studies in Hellenstic theory and practice. 1982:178,181).

Long notes how Ptolemy attempts to stifle critics by asserting that astrology is only one of many things like genetics and social conditions that influence us, that general effects are more powerful than individual effects (which explains the Cannae problem), and that astrologers are fallible (which explains every failure). But "He does not bother to answer the problem of twins" (p.183).

Pico's famous Disputationes
The Italian scholar Giovanni Pico della Mirandola (1463-1494) raised many objections to astrology in his famous 12-volume Disputationes adversus astrologiam divinatricem, which can be grouped as follows (all based on Garin's Astrology in the Renaissance 1983 and Shumaker's The Occult Sciences in the Renaissance 1972:22):

(1) Unsound basis. Astrology is irreligious, leading to impiety and heresy. It is based not on observation (because too complex) but on number mysticism and fallacious analogy.

(2) Disagreement and error. Astrologers disagree widely on method and interpretation, eg Ptolemy rejects what Dorotheus accepts, and they make many errors, eg they do not correct for declination. This is more than the antiquity of astrology should allow.

(3) Many absurdities. Why should details of individual lives be clear when important events involving nations are not? Many astrological ideas are absurd, eg houses (the sky has no inherent properties), elections (how can a fortunate hour for starting a journey make it safe and comfortable?), and predictions (forces that work in the future work more powerfully in the present).

(4) Inutility. Predictions rarely come true, and then only by chance or ambiguity. If astrology merely reinforces a wise judgement, what has been gained? If it contradicts it, why trust astrology over reason?

(5) No physical basis. The stars can act only by light and motion [ie by physical action], which apply universally not individually. Apart from the sun and moon, they affect us hardly at all. In any case, the required accuracy in their positions is not achievable. Today this argument is unremarkable but at the time it was almost unheard of.

(6) Pico especially despised how astrologers reasoned by analogy, eg just as life begins at spring so the zodiac begins at Aries. Such reasoning can prove anything "since nothing exists which ... [cannot be imagined] to have some similarity or dissimilarity with something else", eg just as life began in the sea so the zodiac begins at Pisces.

Pico does not mention the problem of twins. Nevertheless his arguments against astrology, and those of Cicero, remain largely as valid today as they were then.

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