From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 564-565 |
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Ibn Rushd: Abū al‐Walīd Muḥammad
ibn Aḥmad ibn Muḥammad
ibn Rushd al‐Ḥafīd
Miquel Forcada
Alternate
names
Averroes
Died Marrakech
(Morocco), 10 December 1198
Ibn
Rushd, one of the best‐known Islamic philosophers, challenged Ptolemy's
astronomical system on philosophical grounds and made interesting theoretical
contributions to the Andalusian criticisms of the Greek astronomer. Along
with Ibn Bājja, Ibn
Ṭufayl, and Biṭrūjī,
he wished to formulate a model for the cosmos according to Aristotelian principles
– i. e., uniform and circular motions centered on the Earth – in which
there was no need for eccentrics and epicycles. He was also an active and
a first‐rate scholar in many other disciplines, including Islamic religion
and law, medicine, and the various aspects of Hellenistic philosophy.
Ibn
Rushd was born into an important family of religious scholars, but in addition
to religious sciences, he also studied medicine and astronomy. We know little
of his formative period; he probably studied in Cordova and Seville, learning
medicine from a physician named Ibn Jurrayūl. In Seville he met Abū
Jaʿfar
ibn Hārūn al‐Tarjālī, a court physician who also
had a profound knowledge of philosophy and mathematical sciences; Ibn Rushd
became his pupil in these disciplines. In his Summary of the Almagest,
Ibn Rushd himself mentions a master in astronomy named Abū Isḥāq ibn Wādiʿ, who is otherwise unknown.
We know that in 1153 Ibn Rushd was in the service of the Almohads, a North
African dynasty that ruled Muslim Spain (al‐Andalus) and North Africa
for many years. In 1153, according to his commentaries to Aristotle's
De Caelo, he observed several stars in Marrakech. In the Summary
of the Almagest, Ibn Rushd goes on to say that he calculated the positions
of Venus and Mercury, under the supervision of Abū Isḥāq
ibn Wādiʿ,
in order to check a conjunction of these planets with the Sun allegedly observed
by the nephew of the Andalusian astronomer Ibn
Muʿādh. These autobiographical
data, together with his treatise on the Almagest, bear witness to a
thorough knowledge of the fundamentals of astronomy, though he did not pursue
these studies in his later years.
The personal
and intellectual sides of Ibn Rushd's life are inseparable, and both were
decisively determined by the fortunes of the Almohad dynasty. These rulers
had attained power advocating a new interpretation of Islam that was based
on the thought of Ibn Tūmārt. The new ideology had a rationalistic
side applied to religion that favored the growth of rational speculation and,
therefore, of philosophy and science. Furthermore, between 1163 and 1184 the
dynasty was ruled by Caliph Abū Yaʿqūb Yūsuf, a man of learning interested
in philosophy, medicine, and astronomy, to whom Ibn Rushd was introduced,
perhaps about 1169, by the philosopher and court physician Ibn Ṭufayl. According to the chronicles, Caliph
talked with the two philosophers about complex issues of faith and philosophy
such as the eternity of the world. Ibn Ṭufayl
later told Ibn Rushd that the caliph had complained about the obscurity of
Aristotle's texts and wished to find someone able to explain them and make
them more generally accessible. Whether or not this story is true, Ibn Rushd
spent the rest of his life involved in this task, and became the leading commentator
on Aristotle, while working for the court administration as physician, judge,
and theologian. He held the posts of judge of Seville (1169) and Cordova (1171)
and later became chief judge of Cordova (1182); also in 1182, he succeeded
Ibn Ṭufayl
as the caliph's doctor. By this time, Ibn Rushd had been promoted to the highest
ranks of the Almohad hierarchy because of his intellectual activity, mainly
in the fields of medicine and law. During his last years (1195–1197), he fell
into disgrace and was prosecuted together with other intellectuals because
Caliph al‐Manṣūr,
challenged by the Christians, sought to gain the favor of a party of influential
religious scholars who were hostile to the growth of philosophical speculation.
He was exiled to Lucena (south of Cordova), but shortly before his death Ibn
Rushd was rehabilitated and returned to the capital of the kingdom.
Ibn
Rushd wrote his most important work on astronomy, the Mukhtaṣar al‐Majisṭī
(Summary of the Almagest), at the beginning of his career, sometime
between 1159 and 1162. Perhaps under the influence of Ibn Bājja, it was
written in a period characterized by his search for those aspects of science
necessary for human perfection. For this reason, his astronomical work shares
many features with his medical writings, especially the Kulliyyāt
fī al‐ṭibb (Generalities on medicine),
where (also under the influence of Ibn Bājja) Ibn Rushd discusses the
role of philosophy for dealing with scientific materials. However, being less
expert than in medicine, his Summary of the Almagest is more an attempt
to understand the scope of theoretical astronomy in his time rather than an
attempt at an authoritative work such as represented by the Kulliyyāt.
Ibn Rushd asks to what extent astronomy can be considered a true science and
deals not only with mathematical astronomy but also with the physical representation
of the cosmos. He discusses Ptolemy, comparing and contrasting his work to
some of the most important Arabic and Andalusian mathematical astronomers
who criticized parts of his system but respected its fundamentals. Ibn Rushd's
main sources are the Iṣlāḥ al‐Majisṭī
(Corrections to the Almagest) of the Andalusian Jābir
ibn Aflaḥ,
the Kitāb fī hayʾat al‐ʿālam (Book on the configuration
of the World) and al‐Shukūk ʿalā
Baṭlamyūs of the Egyptian Ibn
al‐Haytham, and the treatises by the Andalusian Zarqālī
on the motion of the fixed stars and on the Sun. Though he seems convinced
that astronomy needs to be thoroughly redefined, in the meantime he is obliged
to rely upon the questions on which all the astronomers agree. His short commentaries
(jawāmiʿ) to Aristotle's works (generally written during the
same period of his life) reflect the doubtful opinions expressed in the Mukhtaṣar
al‐Majisṭī.
Underlying his short commentaries to the De Caelo and Metaphysics
is the paradigm of contemporary astronomy even though it contradicts Aristotle.
However, Ibn Rushd disagrees with Ptolemy and Islamic astronomers on many
points such as the existence of a ninth sphere. To deal with these contradictions,
he uses ambiguous explanations such as the metaphor of the “universal animal”
(ḥayawān kullī) found in Ptolemy's Planetary
Hypothesis, also echoed in Ibn Ṭufayl's Risālat Ḥayy ibn Yaqẓān, which he uses to pose
the problem of the existence of several motions in the planets in different
directions.
Ibn
Rushd's opinions evolved during the second period of his work, which was characterized
by a strict reading of Aristotle, freeing it from the opinions that both Hellenistic
and Islamic philosophy had added to it. For this reason, in his long commentaries
(tafāsīr) to De Caelo and the Metaphysics in
particular, he openly rejects the existence of eccentrics and epicycles insofar
as they contradict the necessity of circular and uniform motions around the
Earth for the planets. The main problem is that Ibn Rushd is not aware of
the astronomical theories formulated by Eudoxus
and Callippus
that underlie the Aristotelian cosmos and so has great difficulty in understanding
Aristotle's texts on this point. Having no time and insufficient knowledge
(as he himself confesses) to formulate a new proposal that allows the coexistence
in the same model of the apparent planetary motions alongside Aristotelian
tenets, he only suggests that planets have a spiral movement that accounts
for both daily motion and motion in longitude. This intuitive idea based on
the observation of the Sun (also shared by Biṭrūjī) has some precedents
in Plato
and Theon of
Alexandria, but in Ibn Rushd seems to have sprung from a misreading
of Aristotle.
Carmody, Francis J. (1952). “The Planetary Theory of Ibn Rushd.”
Osiris 10: 556–586.
Cruz
Hernández, Miguel (1997). Abū l‐Walīd Ibn Rushd (Averroes):
Vida, obra, pensamiento e influencia. 2nd
ed. Cordova: Caja Provincial de Ahorros.
Daiber, Hans (1999). Bibliography of Islamic Philosophy.
2 vols. Leiden: Brill. (An exhaustive bibliographical repertory, which contains
the list of edited works in vol. 1, pp. 449–468, and a most complete bibliography
on Ibn Rushd, mainly as a philosopher, in vol. 2, pp. 231–262.)
Endress, Gerhard (1995). “Averroes' De Caelo: Ibn Rushd's
Cosmology in his Commentaries on Aristotle's On the Heavens.” Arabic
Sciences and Philosophy 5: 9–49.
——— (2003). “Mathematics
and Philosophy in Medieval Islam.” In The Enterprise of Science in Islam:
New Perspectives, edited by Jan P. Hogendijk and Abdelhamid I. Sabra,
pp. 121–176. Cambridge, Massachusetts: MIT Press.
Forcada,
Miquel (1999). “La ciencia en Averroes.” In
Averroes y los averroísmos: Actas del III Congreso Nacional de Filosofía
Medieval, pp. 49–102. Zaragoza: Sociedad de Filosofia Medieval.
Hugonnard‐Roche,
H. (1977). “Remarques sur l'évolution doctrinale d'Averroès dans les commentaires
au De Caelo: Le problème du mouvement de la terre.” Mélanges
de la Casa de Velazquez 13: 103–117.
———
(1985). “L'épitomé du De Caelo d'Aristote par Averroès: Questions de
méthode et de doctrine.” Archives d'histoire doctrinale et littéraire
du moyen âge 52: 7–39.
Lay,
Juliane (1996). “L'Abrégé de l'Almageste: Un inédit d'Averroès en version
hebraïque.” Arabic Sciences and Philosophy 6: 23–61.
Sabra,
A. I. (1994). “The Andalusian Revolt against Ptolemaic
Astronomy: Averroes and al‐Bitrūjī.” In Transformation
and Tradition in the Sciences, edited by Everett Mendelsohn, pp. 133–153.
Cambridge: Cambridge University Press. (Reprinted in Sabra, Optics, Astronomy
and Logic, XV. Aldershot: Ashgate.)
Samsó,
Julio (1992). Las ciencias de los antiguos en al‐Andalus. Madrid:
Mapfre.
Urvoy, Dominque (1991). Ibn Rushd (Averroes). (Translated
by Olivia Stewart. London: Routledge.)