Detail Of The Tondo Portraying St. Albertus Magnus For The Painting Crucifixion - Museum of Saint Mark, Florence.
let them be for signs

Albertus Magnus &
Prognostication by the Stars

Sue Toohey

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An oft-repeated story informs us that a writer from the twelfth century told of how he had been at Jaffa [1] when a new ship was about to sail. Being known as an astrologer, he was asked to determine what fate the stars held for this vessel. Calculating the positions of the heavenly bodies, he began to tremble as he realised the ship was destined to falter. The writer escaped disaster by not boarding the vessel, but the crew decided to sail despite warnings of the imminent demise of their ship. As predicted, soon after leaving the harbour the vessel was shipwrecked leaving no survivors. This was a senseless waste of life and one that was, perhaps, preventable. Had the stars merely warned of potential danger, or had they foretold an unavoidable fate? Could the use of judicial astrology under these circumstances be justified to save lives or was reading the stars to open oneself to consorting with the devil?

A high level of acceptance for judicial astrology was found among Church authorities of the Middle Ages. The study of works by Albertus Magnus (c. 1206-1280), Roger Bacon (c. 1214-1294), and Thomas Aquinas (c. 1227-1274), shows beyond doubt that the astrological viewpoint characterised medieval conceptions of nature and the historical world. According to philosophy historian Paola Zambelli, the principle of the influence of celestial movements on natural processes was unanimously upheld by medieval theologians, philosophers, and scientists. [2] Even though these beliefs, or at least enquiry into these beliefs, went against the religious orthodoxy of the day, people continued to examine and write about these matters. Even the most critical of opponents could not deny some correlation between a person's temperament and the configuration of their natal horoscope. Almost no one denied the usefulness of the astral conjunctions for determining history or predicting tragic events related to empires or religious and major natural disasters.
Astrological Writers of the Church
Albertus Magnus, Thomas Aquinas, and Roger Bacon all wrote comprehensively about astrology. Albertus cites Ptolemy to show that astrologers do not believe in fatal necessity and that, consequently, the art of astrology is not irreconcilable with Christianity. [3] He argues that neither fate, nor stars, nor even providence takes from human free will its liberty of action, rejecting the notion of absolute fatal necessity as heretical. Bacon forwards similar arguments when describing the difference between forbidden and legitimate judicial astrology. The forbidden, says Bacon, ascribes fatal necessity to the influence of the stars. He shows by examining the writings of those astrologers he calls learned and legitimate that genuine astrologers have never held to the tenet of fatal necessity. In principle, it was agreed that everyone has the power to prevail over astral influences. Bacon, Aquinas and Albertus concurred in their views that the stars can influence the body and that the body, in turn, can influence the soul. The stars, by their influence on the human body, incline men to bad acts and evil arts, or to good conduct and the useful sciences, according to Bacon. Such natural inclinations might, however, be resisted by the power of will, modified by divine grace, or strengthened by diabolic tempting. However, although the individual may resist the force of the stars by an effort of will, for most people the power of the constellations usually prevails. Similarly, most people, according to Aquinas, are ruled by their bodily passions or 'appetites' and very few have the intellect and will that is needed to overcome their baser impulses. For the bulk of humanity, the influences of the stars upon the body, therefore, go unimpeded. However, the will remains free and those who exert themselves may counter the effects of the stars.

The concept of free will, according to Aquinas, demonstrates the endeavour to find a synthesis with and reinforcement of the Church's claim to universality. [4] Aquinas believed that individuals have freedom of moral choice without in any way detracting from God's omnipotence, because free will is in harmony with the essence of the universe, and with its structure of hierarchically descending powers by means of which God unfolds his nature. Nor should divine providence be seen in any way as a constraint upon human autonomy because freedom of the will is itself a participation in the providential government of the cosmos. He explains in Summa Theologica how it is possible for astrologers to predict future events regardless of free will: [5]

The majority of men follow their passions ... few are wise enough to resist these passions. Consequently, astrologers are able to foretell the truth in the majority of cases, especially in a general way. But not in particular cases; for nothing prevents man resisting his passions by his free-will. Wherefore the astrologers themselves are wont to say that "the wise man is stronger than the stars", forasmuch as, to wit, he conquers his passions.

In other words, it is not with the help of demons that astrologers are able to predict the future but because humans are predictable in their nature.

Albertus Magnus, author of Speculum Astronomiae, [6] argues forthrightly against those who condemned astrology. Convinced that the science of astrology constitutes an essential contribution to epistemology, he is openly polemical against those who would suppress astrological texts. His view was that any suppression would soon need to be reversed, as he explains in his Speculum Astronomiae: [7]

And the readers of the aforementioned books already know that not even a single word is found in them that might be or might seem to be against the honour of the catholic faith nor, perhaps, is it fair that those who have never touched these (books) should presume to judge them.

What Albertus is arguing is that anyone who had read the suppressed astrological texts would know that they contain nothing contrary to the Catholic faith, and those who had not read them had no recourse to judge them. According to Albertus, the art of interrogations (horary astrology) was, under most circumstances, consistent with freedom of the will. If predicting the weather is deemed natural and acceptable, why should the celestial positions not be used to forecast other events? What use is the theory of astrology without the ability to apply it to meaningful situations?

It has frequently been argued that the exploration of natal horoscopes was the section of astrology that offended the notion of free will more severely than any other. But Albertus clearly counters this belief. By his understanding, every operation of a cause acting on something is determined in accordance with the proportion of material receiving that operation, as, for example, the same fire drying mud yet melting wax. He gives the example of a man, knowing in advance that he is going to be facing an overabundance of heat and dryness from the operation of the heavens, changing his temperament a long time beforehand by organising his diet until it inclines on the side of coldness and wetness, so that the additional heat brings him back to a moderate temperament instead of causing harm. An impediment that is foreseen may potentially be removed, totally or in part, by which the operation of heaven is not frustrated, but perfected. Albertus quotes Ptolemy's Centiloquium where it is said: [8]

An astrologer can avert a great deal from the operation of the stars when he is informed about the nature acting upon him, and has prepared himself before its descent so that the one who will receive the influence will be able to bear it.

Albertus goes on to say that a future positive, if foreseen, can be increased and its advantages optimised. Again, quoting Ptolemy's Centiloquium: [9]

The knowing soul can help the celestial operation, just as the sower can help the strength of plants through careful cultivation and weeding.

So, while the heavens will always proceed in a way that pertains to its nature, it is always possible for those who receive this process from the heavens to do so in a way that is beneficial to their own nature when they recognise and comprehend what is to come.
Interrogations [10]
During the 13th century, the debate on astrology and free will was a fierce one, with scholars pondering all shades of arguments for and against astral necessity. Albertus was clearly opposed to the suggestion of astral necessity, particularly rejecting the idea that corporeal motions follow those of the superior world, but the motions of the soul do not. His views on the relationship between astral influences and free will remain consistent throughout all his writings. In Summa theologiae [11] he says that inclinations are derived from the stars, but those inclinations should never be considered essential. He defines astrological prophecy as probable by insisting on the Ptolemaic concept of ‘stellae secundae’, with which he was very familiar.[12]

Astrologers predict future events from first causes, which do not impose any necessity; and hence their judgement is not necessary, but - as Ptolemy says - conjectural according to variations in the secondary causes. It is for this reason that Ptolemy says that the prediction is more certain, if we can know the powers of higher causes as they are incorporated in the secondary causes; and he calls these secondary stars.

Zambelli explains that since astrology gives the apparent forecast of mixed-effects partly dependent on sublunar components, its cautious and sensible practice enables us to postpone, modify or even avoid some of the inauspicious effects of astral causality. Albertus says: [13]

Those qualities, because of contrary natural properties and different dispositions found in matter, often exclude the effects of heavenly motions. For this reason Ptolemy says that 'The wise men dominate the stars'.

In Speculum, Albertus discusses the work of John of Seville called Prima Pars Artis (The first Part of the Art). Albertus explains that the section devoted to interrogations teaches astrologers:

how to make judgements concerning that thing about which the interrogation has been made with a radical intention - to know, idly, whether it will come to pass or not. And if the answer is positive, what might be its cause and when will it occur? And if the answer is negative, what prevents it from happening, and when will something happen that ought not to happen - that is, to judge this by means of the involvement of the signifier, which is the lord of the interrogation, with the lord of the thing asked, or with a benefic planet, or with a recipient or one received, I mean involvement through conjunction or aspect, also transference and collocations [14] and - what is altogether beyond these - because the zodiacal circle at that hour is in accordance with the intention of the interrogator. [15]

Albertus then lists a number of books where information on these things can be found, including De receptionibus (On Receptions) by Mashallah and De interrogationibus (On Interrogations) by Zahel.[16]

In Chapter 14 of Speculum, Albertus writes about the use of interrogational astrology and its relationship with free will. He differentiates between questions concerning the past, and those concerning that which is not yet determined, giving examples of questions involving someone who is absent and whether they are dead or alive, whether rumours are true or false, the sex of a baby already born, or whether the work of a man who professes alchemy is true or not. The truth of these, according to Albertus, has already been determined by what he refers to as “the other direction”. That is, the stars have already imprinted their influence onto the earthly plane and the events are able to be determined by astrological investigation. These events are characteristic of the nature of things that are signified by the heavens. It does not involve predicting the future but rather determining what has already happened. This may seem unnecessary, but in days of poor communication it was often difficult to discover news and people would sometimes wait months to hear word of a significant event. Astrological interrogations were a means to discover what had occurred and William Lilly was often consulted about such matters, for example, when ships had become long overdue from their journey at sea, or to discover the fate of soldiers at war.

Similarly, Hildegard of Bingen, writing a century earlier than Albertus, stated that the stars sometimes show many signs, not of the future or hidden thoughts of men, but of matters which have already been revealed by act of will or voice or deed. The air, according to Hildegard, has already received an impression of these actions, which the stars can reflect back to others if God allows it. At times the stars display many signs, depending on what humans are then accomplishing in their actions. They disclose neither future events nor human thoughts, but only as much as human beings already disclose of their own accord or accomplish by word or deed. [17]

According to Albertus, questions concerning the future admit uncertainty. Some questions asking about future possibilities have greater uncertainty than others and it is these questions that are commonly subject to free will. There are some things asked about that no one can impede. Albertus gives the price of grain as an example of a question that cannot be impeded on. What he means by this is that such a question cannot be influenced and is not dependent on free will. He points out, however, that these types of questions are best answered by an examination of the revolutions (that is, transits) rather than by the method of interrogational astrology.

Albertus spends some time discussing the issues of interrogations and explains there are two kinds of questions about contingent things that are subject to free will. These are questions dealing with matters of fact (what will happen concerning something?) and those of advice (would it be better to do this or that?). Questions about advice do not destroy the freedom of the will. On the contrary, according to Albertus, they rectify and direct it. To destroy the books concerning these things would be more against the advocacy of free will than for it, because to take advice and negotiate is one of the persuasive means by which it is demonstrated that everything does not happen due to necessity, but that some things happen by chance and the result could go either way. He offers examples of questions such as whether a business negotiation might be useful or not, about which of two things it might be better to buy, and about a route that someone intends to take, whether it might be better to proceed or delay? All of these questions presuppose that the person asking the question has the free will to choose the option best suited to their situation.

Albertus does, however, raise concern about the difficulty of reconciling interrogations of fact with the concept of freedom of the will. The example he uses is of a question of money being sought from someone (whether they will pay what they owe or not?). Even if it was signified that this person will not give the money he is, nevertheless, always free to give it by the volition of free will. Similarly, if it was signified that this person is going to give it, he is always free to choose not to give it. In other words, even if the chart shows a predictable course of action, the subject is free to make another choice and change the predicted outcome. The conclusion that Albertus reaches is an interesting explanation of why he considered that free will is not inhibited by interrogations, and how interrogations and free will are valid together: [18]

... God knew from eternity which of these he (the man) would choose. For which reason, in the book of the universe, which is the vellum of heaven. He was able to configure, if He wished, what He knew; [but] if He did this, then the compatibility of free will with divine providence or with the indication of an interrogation is the same. Therefore, if it cannot be denied that divine providence co-exists with free will, it cannot be denied that the profession of interrogations co-exists with it as well.

However, interrogations will not always present an unambiguous answer as Albertus explains: [19]

... When the signifiers are equal in good fortune and evil, the counsel of the profession of the stars is to abandon the interrogation since God wished to keep it hidden from us.

God will sometimes choose to keep the answer concealed, thereby making it impossible to read the chart. However, Albertus turns to the work of John of Seville to demonstrate potential ways to counter the lack of clarity in the chart.

...if the signifiers of the interrogation are equal in good fortune and bad fortune, it [Prima pars artis] teaches one how to help the situation with (a) the ascendant of the conjunction or opposition which occurred before the interrogation, and (b] with the almuten of the degree of that conjunction or opposition which is the animodar [20] in nativities, especially if it has some dignity in the ascendant of the interrogation. [21]

Albertus appears to be suggesting that if the answer to the chart is not clear, then for supplementary advice take the moment of the perfection of the conjunction or opposition that occurred immediately prior to the question being asked and use that time to construct a new chart. So, for example, if the interrogation chart has a separating opposition, find the time of perfection for the opposition and generate a new chart using the time of perfection along with the almuten of the degree of perfection.

It is not apparent what the Church thought of the stance that Albertus took and his outspoken defence of judicial astrology. Albertus and Aquinas were both canonised by the Catholic Church, suggesting that their support of astrology was seen as no impediment to their eminence as Church Fathers. Dante frequently mentions them both and is guided in his masterpiece 'The Divine Comedy' by the doctrine of free will proposed by Albertus. He sees both Albertus and Aquinas as the great lovers of wisdom and places them in the Heaven of the Sun. By allowing that interrogations will not always give the answer, or that God can choose not to reveal the answer, Albertus cleverly puts control back into the hands of God and not astrology. Similarly, questions of advice put the control back into the hands of the person asking the question, thereby emphasising freedom of the will. The works of a vast array of astrologers writing in the Middle Ages show that, contrary to the beliefs of many modern-day astrologers, astral determinism was not a constant theme at this time. Although most of the arguments against a fatalistic view of astrology were closely tied to God in a way that is not seen today, they demonstrate unmistakably that a belief in the astrology of interrogations did not inhibit one’s free will but rather enhanced it and curated it.
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Resources & related links

Ptolemy's Centiloquium | The Speculum Astronomiae and Its Enigma by Paola Zambelli
Speculum Astronomiae the original Latin text by Albertus Magnus


Speculum Astronomiae Latin edition

Sophia Centre for the Study of Cosmology in Culture
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Notes & References:
1 ] Jaffa is a port on the Mediterranean Coast at Palestine. It is believed to be the oldest port that has been continually in existence having been established by the Canaanites in the 18th century BCE and used by the Egyptians and Phoenicians. It is currently occupied by Israel.
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2 ] Paola Zambelli, The Speculum Astronomiae and its Enigma - Astrology, Theology and Science in Albertus Magnus and his Contemporaries, ed. Robert S. Cohen, vol. 153, Boston Studies in the Philosophy of Science (Dordrecht: Kluwer Academic Publishers, 1992).p. xiii
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3 ] Lynn Thorndike, History of Magic and Experimental Sciences, 1-8 vols. (New York: Columbia University Press, 1923).vol 2, p. 585.
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4 ] Charles Trinkaus, "The Problem of Free Will in the Renaissance and the Reformation," Journal of the History of Ideas vol 10, no. 1 (1949), p. 51.
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5 ] Thomas Aquinas, The Summa Theologica (Clevland: Benziger Bros, 1947).1a, q 115, a4.
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6 ] Roger Bacon has also been proposed as the author of this work, though most scholars agree that it was the work of Albertus and I write this article based on that belief.
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7 ] Albertus Magnus, "Speculum Astronomiae" in The Speculum Astronomiae and Its Enigma - Astrology, Theology and Science in Albertus Magnus and His Contemporaries, ed. Robert S. Cohen (Dordrecht: Kluwer Academic Publishers, 1992).p. 219.
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8 ] Ibid., p. 259. [Aphorism 5. Henry Coley's translation of Ptolemy's Centiloquium is available on this site at]
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9 ] Ibid. [Aphorism 8 (see above).]
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10 ] Interrogations, in the sense that it is used in this article, is better known today as horary.
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11 ] Not to be confused with the work of the same id by Thomas Aquinas.
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12 ] Magnus, "Speculum Astronomiae." p. 71.
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13 ] Ibid. This well known quote, sapiens homo dominatur astris,has most frequently been attributed to Ptolemy, supposedly from Almagest. However, it does not appear in any of Ptolemy's writings. It is clearly a favourite for Albertus as he mentions it in several of his books including Speculum, De fato, De natura locorum and the Summa theologiae.In fact, it appears to have been a favourite for many authors during this period including Thomas Aquinas who also quoted it in his Summa theologiae.
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14 ] Grouping together of things in a certain order.
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15 ] Magnus, "Speculum Astronomiae" p. 261.
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16 ] One of the most valuable things about Speculum from a modern point of view is the significant number of works Albertus lists as being available to him. This list was extensive and is ample evidence to the testament that the subject of astrology was a predominant feature of life at that time.
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17 ] Hildegard of Bingen, On Natural Philosophy and Medicine: Selections from Cause et cure, ed. Jane Chance, trans. Margret Berger, Library of Medieval Women (Cambridge: D.S.Brewer, 1999).p. 33. Interestingly, Hildegard often spoke of her disapproval of astrology yet she was known to have used conception charts and the phases of the Moon to determine someone's character.
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18 ] Magnus, "Speculum Astronomiae" p. 267.
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19 ] Ibid.
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20 ] This is a term used by Ptolemy in his process of rectification. In Tetrabiblos, III.2, Ptolemy describes a similar process when attempting to find the ascendant of a natal chart when the time is unknown.
[See the glossary item at]
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21 ] Magnus, "Speculum Astronomiae" p. 262.
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Australian astrologer Sue Toohey (1961-2007) wrote this article whilst pursuing a doctorate in Classics, History and Religion at the Mary White College University of Armidale, New South Wales, Australia. Sue had majored in history and philosophy, held a master's degree in the history of religious thought in the Middle Ages and Renaissance periods, and her specialist area of research was divination in antiquity with particular reference to the principle of correspondences in the ancient world.
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