| From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 550-551 |
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Ibn Bājja:
Abū Bakr Muḥammad
ibn Yaḥyā ibn al‐Ṣāʾigh al‐Tujībī al‐Andalusī
al‐Saraqusṭī
Miquel Forcada
Alternate
names
Avempace
Died Fez, (Morocco),
June or July 1139
Ibn
Bājja, one of the most important philosophers of Muslim Spain, was in
the forefront of the 12th‐century Andalusian movement to criticize and
replace Ptolemaic astronomy based on Aristotelian principles. In addition
to astronomy, he was also active in other scientific disciplines, such as
mathematics, botany, pharmacology, and medicine. Ibn Bājja learned philosophy
and other sciences in an environment that was deeply influenced by the court,
ruled at that time by the Banū Hūd dynasty whose kings were patrons
of science and scientists. Under their protection, Saragossa became an important
center of both philosophical and mathematical studies. Ibn Bājja also
mastered poetry and other disciplines that were based on the Arabic language
and Islamic teachings. The Banū Hūd were ousted from Saragossa in
1110, but Ibn Bājja was employed by the city's new Almoravid governor,
Ibn Tīfalwīt, whom he served for 3 years, though the exact dates
are not known. The governor sent him as ambassador to ʿImād
al‐Dawla ibn Hūd, the former ruler of Saragossa who had established
his court in Rueda de Jalón. The latter imprisoned him for several months.
Ibn Bājja returned to Saragossa but soon left, perhaps because of the
death of his protector Ibn Tīfalwīt (1117). The city would be occupied
by the Christians in the following year. From that point on, his life became
a long pilgrimage that took him to several cities in Muslim Spain and North
Africa – Xàtiva, Almeria Granada, Oran, and perhaps Seville – though he never
settled. According to some sources, Ibn Bājja held the post of minister
to Yaḥyā ibn Yūsuf ibn Tāshifīn, governor
of Fez, though some scholars disagree. Nonetheless, this episode, together
with his period in the service of Ibn Tīfalwīt, is proof of his
relationship with the Almoravid dynasty in spite of his scientific and philosophical
career. The Almoravids based their legitimacy on religious observance and
were therefore hostile to philosophy and other disciplines that could challenge
their concept of orthodoxy. Ibn Bājja was imprisoned at least once by
the Almoravids in Xàtiva for heterodoxy, but, apparently, the episode had
no further consequences. It appears that he spent the last period of his life
far from the court, occupied in his intellectual work and earning a living
as a physician. However, the many challenges he had to confront during his
life seem to have interfered with his intellectual work, as we find a large
number of short, fragmentary, and incomplete treatises. The story of Ibn Bājja's
death bears witness to the turbulence of the times, as he is said to have
been poisoned by order of Abū al‐ʿAlāʾ
Zuhr, a member of the most important dynasty of court physicians in Muslim
Spain, whether or not the story is true, other sources seem to attest to the
enmity between the two scientists, an enmity that combined personal rivalry
and religious considerations.
Ibn
Bājja's work in natural philosophy has certain implications for the history
of astronomy. In his commentaries on Aristotle's
Physics he accepted – diverging from Aristotle, and supporting John
Philoponus – the possibility of motion in the void or in a medium
that does not exert resistance, as happens in the celestial bodies, thus applying
the physical principles of the sublunary world to the heavens. These ideas
were echoed by European Scholastics, and from there may have influenced Galileo
Galilei. However, this conception of dynamics cannot be traced, for
the moment, in Ibn Bājja's astronomical thought.
The importance of Ibn Bājja's astronomy lies in the fact that
he seems to have been the first of the Andalusians to develop a criticism
of Ptolemy
based on philosophical tenets (the others being Ibn
Ṭufayl, Ibn
Rushd, and Biṭrūjī). They
wished to formulate a cosmos according to Aristotelian principles (uniform
and circular motions centered on the Earth) in which planetary models had
no need of eccentrics and epicycles. According to Maimonides
in The Guide of the Perplexed, Ibn Bājja accepted eccentrics but
not epicycles. However, a deeper study of his extant works has revealed two
important, and hitherto unremarked, facts: On the one hand, Ibn Bājja
must have had a profound knowledge of mathematical astronomy (consistent with
the fact that he was a mathematician), and the information found in a range
of sources, including his own letters, reveal that he observed an occultation
of Jupiter by Mars, observed solar transits of Venus and Mercury (seemingly
a confusion with sunspots), and predicted a lunar eclipse. On the other hand,
Ibn Bājja must originally have been a follower of Ptolemy. In a letter
addressed to Abū Jaʿfar Yūsuf
ibn Ḥasdāy, he attacks Ibn
al‐Haytham, one of the most important mathematical astronomers
who criticized Ptolemy, arguing that Ibn al‐Haytham did not understand
Ptolemy's models for Mercury and Venus, something that is fairly clear in
the case of Mercury. Again on the subject of Mercury, he disagrees with the
Andalusian astronomer Zarqālī,
who formulated some alternative models to Ptolemy. Besides, in his commentary
to Aristotle's Physics, Ibn Bājja introduces a digression following
Philoponus in which he accepts the existence of epicycles. However, a short
and incomplete treatise has survived entitled Kalām fī al‐hayʾa
(Discourse on cosmology) that criticizes Ptolemy's method. Here, on the basis
of Aristotelian logic, Ibn Bājja tackles the problem of the relationship
between what the astronomer can observe and the underlying reality and argues
that the planetary models of the Ptolemaic astronomers do not fit the tenets
of Aristotelian scientific method.
Selected References
Al‐ʿAlawī,
Jamal al‐Dīn (1983). Rasāʾil falsafiyya li‐Ibn
Bājja. Beirut. (Edition of the letters of Ibn
Bājja containing texts on astronomy and other sciences.)
Daiber, Hans (1999). Bibliography of Islamic Philosophy.
2 Vols. Leiden: E. J. Brill. (An exhaustive bibliographical repertory, which
contains the list of edited works in Vol. 1, pp. 436–441 and a most complete
bibliography of Ibn Bājja, mainly as a philosopher, Vol. 2, pp. 211–217).
Dunlop, Douglas M.
(1957). “Remarks on the Life and Works of Ibn Bājja (Avempace).” In Proceedings
of the Twenty‐second Congress of Orientalists, edited by Zeki Velidi
Togan, pp. 188–196. Leiden: E. J. Brill.
Endress, Gerhard (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.
Fakhry, Mājid (ed.) (1972). Sharḥ
al‐Samāʿ
al‐Tabīʿi li‐Arīstūtālīs.
Beirut. (Reprint, 1991. One of the most important editions of Ibn Bājja's
commentary on Aristotle's Physics.)
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. (Contains
a survey of the Andalusian criticism of Ptolemy and the role of Ibn Bājja.)
Ibn,
Bājja (1997). El régimen del solitario. Introducción, traducción
y notas de Joaquín Lomba. Madrid: Trotta. (Spanish
translation of one of Ibn Bājja's most important philosophical treatises
written by one of the most important experts in his thought. Contains a complete
and useful introduction dealing with his life and all aspects – including
scientific ones – of Ibn Bājja's thought and a list of manuscripts of
his work as well.)
Lettinck, Paul (1994). Aristotle's Physics and Its
Reception in the Arabic World with an Edition of the Unpublished Parts of
Ibn Bājja's Commentary on the Physics. Leiden: E. J. Brill. (Excellent
translation into English of Ibn Bājja's work on physics, together with
a study that has thrown new light on the question.)
Pines,
Shlomo (1964). “La dynamique d'Ibn Bājja.” In Mélanges Alexandre Koyré.
Vol. 1, L'aventure de la science, pp. 442–468. Paris:
Hermann.
Samsó,
Julio (1993–1994). “Sobre Ibn Bājja y la astronomía.” Sharq
al‐Andalus 10–11: 669–681.
(The most complete study of Ibn Bājja as an astronomer.)
Yafūt, Salīm (1996). “Ibn Bājja wa‐ʿIlm al‐Falak
al‐Baṭlīmūsī.”
In Dirasāt fī Taʾrīkh al‐ʿUlūm
wa‐l‐Ibistīmūlūjya, edited by S. Yafūt,
pp. 65–73. Rabat. (Edits a range of Ibn Bājja's texts on astronomy.)