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107-541: The Gyromax is the trade name for an adjustable mass (or adjustable inertia ) balance wheel used in Patek Philippe wristwatches . Instead of weight adjustment screws on the outside of the rim, as in traditional balances, the Gyromax has turnable weights recessed into the top of the rim. The advantages claimed for this design are that, without projecting weight screws, the diameter of the balance can be increased, giving it

214-445: A Maliki judge, the book also discusses the opinion of other schools, including liberal and conservative ones. Other than this surviving text, bibliographical information shows he wrote a summary of Al-Ghazali's On Legal Theory of Muslim Jurisprudence ( Al-Mustasfa ) and tracts on sacrifices and land tax. In his philosophical writings, Averroes attempted to return to Aristotelianism , which according to him had been distorted by

321-495: A careful reading of the Quran implied only the "form" of the universe was created in time but that its existence has been eternal. Averroes further criticized the mutakallimin for using their interpretations of scripture to answer questions that should have been left to philosophers. Averroes states his political philosophy in his commentary of Plato's Republic . He combines his ideas with Plato's and with Islamic tradition; he considers

428-522: A circle. Buridan's theory was followed up by his pupil Albert of Saxony (1316–1390) and the Oxford Calculators , who performed various experiments which further undermined the Aristotelian model. Their work in turn was elaborated by Nicole Oresme who pioneered the practice of illustrating the laws of motion with graphs. Shortly before Galileo's theory of inertia, Giambattista Benedetti modified

535-417: A condemnation against 15 doctrines—many of which were Aristotelian or Averroist—that he said were in conflict with the doctrines of the church. In 1277, at the request of Pope John XXI , Tempier issued another condemnation, this time targeting 219 theses drawn from many sources, mainly the teachings of Aristotle and Averroes. Averroes received a mixed reception from other Catholic thinkers; Thomas Aquinas ,

642-631: A cultural decline that resulted in the loss of nearly all of the intellectual legacy of the Classical Greek scholars, including Aristotle. Averroes's commentaries, which were translated into Latin and entered western Europe in the thirteenth century, provided an expert account of Aristotle's legacy and made them available again. The influence of his commentaries led to Averroes being referred to simply as "The Commentator" rather than by name in Latin Christian writings. He has been sometimes described as

749-418: A designer was behind the creation and that is God. Averroes's two arguments are teleological in nature and not cosmological like the arguments of Aristotle and most contemporaneous Muslim kalam theologians. Averroes upholds the doctrine of divine unity ( tawhid ) and argues that God has seven divine attributes : knowledge, life, power, will, hearing, vision and speech. He devotes the most attention to

856-448: A fatwa that philosophy is allowed for Muslims and is probably an obligation, at least among those who have the talent for it. Averroes also distinguishes between three modes of discourse: the rhetorical (based on persuasion) accessible to the common masses; the dialectical (based on debate) and often employed by theologians and the ulama (religious scholars); and the demonstrative (based on logical deduction). According to Averroes,

963-1007: A greater variety of subjects" than those of any of his predecessors in the East, including philosophy, medicine, jurisprudence or legal theory, and linguistics. Most of his writings were commentaries on or paraphrasings of the works of Aristotle that—especially the long ones—often contain his original thoughts. According to French author Ernest Renan , Averroes wrote at least 67 original works, including 28 works on philosophy, 20 on medicine, 8 on law, 5 on theology, and 4 on grammar, in addition to his commentaries on most of Aristotle's works and his commentary on Plato 's The Republic . Many of Averroes's works in Arabic did not survive, but their translations into Hebrew or Latin did. For example, of his long commentaries on Aristotle, only "a tiny handful of Arabic manuscript remains". Averroes wrote commentaries on nearly all of Aristotle's surviving works. The only exception

1070-421: A heavy body on a spherical surface concentric with the earth will maintain itself in that state in which it has been; if placed in a movement towards the west (for example), it will maintain itself in that movement." This notion, which is termed "circular inertia" or "horizontal circular inertia" by historians of science, is a precursor to, but is distinct from, Newton's notion of rectilinear inertia. For Galileo,

1177-414: A larger moment of inertia , and that it has less air resistance. The Gyromax balance has six to eight small turnable weights that fit on pins located in recesses around the top of the balance wheel rim. Each of the weights, called collets , has a cutout making it heavier on one side. When the collet's cutout points to the outside of the balance wheel, the heavier side is toward the center which decreases

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1284-402: A leading Catholic thinker of the thirteenth century, relied extensively on Averroes's interpretation of Aristotle but disagreed with him on many points. For example, he wrote a detailed attack on Averroes's theory that all humans share the same intellect. He also opposed Averroes on the eternity of the universe and divine providence . The Catholic Church's condemnations of 1270 and 1277, and

1391-454: A motion is " horizontal " if it does not carry the moving body towards or away from the center of the Earth, and for him, "a ship, for instance, having once received some impetus through the tranquil sea, would move continually around our globe without ever stopping." It is also worth noting that Galileo later (in 1632) concluded that based on this initial premise of inertia, it is impossible to tell

1498-441: A physical consequence of Descartes ' geometrization of space-matter, combined with the immutability of God." The first physicist to completely break away from the Aristotelian model of motion was Isaac Beeckman in 1614. The term "inertia" was first introduced by Johannes Kepler in his Epitome Astronomiae Copernicanae (published in three parts from 1617 to 1621). However, the meaning of Kepler's term, which he derived from

1605-470: A possible insult to the caliph in his writings but modern scholars attribute it to political reasons. The Encyclopaedia of Islam said the caliph distanced himself from Averroes to gain support from more orthodox ulema , who opposed Averroes and whose support al-Mansur needed for his war against Christian kingdoms. Historian of Islamic philosophy Majid Fakhry also wrote that public pressure from traditional Maliki jurists who were opposed to Averroes played

1712-514: A prestigious office that his grandfather had once held. In 1184 Caliph Abu Yaqub died and was succeeded by Abu Yusuf Yaqub. Initially, Averroes remained in royal favour, but in 1195, his fortune reversed. Various charges were made against him, and a tribunal in Córdoba tried him. The tribunal condemned his teachings, ordered the burning of his works and banished Averroes to nearby Lucena . Early biographers' reasons for this fall from grace include

1819-524: A regular meeting of philosophers, physicians and poets in Seville which was attended by philosophers Ibn Tufayl and Ibn Zuhr as well as the future caliph Abu Yusuf Yaqub . He also studied the kalam theology of the Ashari school, which he criticized later in life. His 13th-century biographer Ibn al-Abbar said he was more interested in the study of law and its principles ( usul ) than that of hadith and he

1926-435: A right line, except insofar as it is compelled to change that state by forces impressed thereon. In his 1687 work Philosophiæ Naturalis Principia Mathematica , Newton defined inertia as a property: DEFINITION III. The vis insita , or innate force of matter, is a power of resisting by which every body, as much as in it lies, endeavours to persevere in its present state, whether it be of rest or of moving uniformly forward in

2033-525: A right line, unless it is compelled to change that state by forces impressed thereon. Despite having defined the concept in his laws of motion, Newton did not actually use the term "inertia.” In fact, he originally viewed the respective phenomena as being caused by "innate forces" inherent in matter which resist any acceleration. Given this perspective, and borrowing from Kepler, Newton conceived of "inertia" as "the innate force possessed by an object which resists changes in motion", thus defining "inertia" to mean

2140-590: A right line. Professor John H. Lienhard points out the Mozi – based on a Chinese text from the Warring States period (475–221 BCE) – as having given the first description of inertia. Before the European Renaissance , the prevailing theory of motion in western philosophy was that of Aristotle (384–322 BCE). On the surface of the Earth, the inertia property of physical objects is often masked by gravity and

2247-611: A role. After a few years, Averroes returned to court in Marrakesh and was again in the caliph's favor. He died shortly afterwards, on 11 December 1198 (9 Safar 595 in the Islamic calendar). He was initially buried in North Africa . His body was later moved to Córdoba for another funeral, at which future Sufi mystic and philosopher ibn Arabi (1165–1240) was present. Averroes was a prolific writer and his works, according to Fakhry, "covered

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2354-458: A royal physician, but his qualification and education was mostly theoretical. For the most part, Averroes's medical work Al-Kulliyat fi al-Tibb follows the medical doctrine of Galen, an influential Greek physician and author from the second century, which was based on the four humors —blood, yellow bile, black bile, and phlegm, whose balance is necessary for the health of the human body. Averroes's original contributions include his observations on

2461-471: A student of his grandfather. His father also taught him about jurisprudence, including on Imam Malik 's magnum opus the Muwatta , which Averroes went on to memorize. He studied medicine under Abu Jafar Jarim al-Tajail, who probably taught him philosophy too. He also knew the works of the philosopher Ibn Bajjah (also known as Avempace), and might have known him personally or been tutored by him. He joined

2568-575: Is Politics , which he did not have access to, so he wrote commentaries on Plato's Republic . He classified his commentaries into three categories that modern scholars have named short , middle and long commentaries. Most of the short commentaries ( jami ) were written early in his career and contain summaries of Aristotlean doctrines. The middle commentaries ( talkhis ) contain paraphrases that clarify and simplify Aristotle's original text. The middle commentaries were probably written in response to his patron caliph Abu Yaqub Yusuf's complaints about

2675-413: Is rotational inertia (→ moment of inertia ), the property that a rotating rigid body maintains its state of uniform rotational motion. Its angular momentum remains unchanged unless an external torque is applied; this is called conservation of angular momentum. Rotational inertia is often considered in relation to a rigid body. For example, a gyroscope uses the property that it resists any change in

2782-797: Is "Abū l-Walīd Muḥammad ibn ʾAḥmad Ibn Rushd". Sometimes, the nickname al-Hafid ("The Grandson") is appended to his name, to distinguish him from his grandfather, a famous judge and jurist. "Averroes" is the Medieval Latin form of "Ibn Rushd"; it was derived from the Spanish pronunciation of the original Arabic name, wherein "Ibn" becomes "Aben" or "Aven". Other forms of the name in European languages include "Ibin-Ros-din", "Filius Rosadis", "Ibn-Rusid", "Ben-Raxid", "Ibn-Ruschod", "Den-Resched", "Aben-Rassad", "Aben-Rasd", "Aben-Rust", "Avenrosdy", "Avenryz", "Adveroys", "Benroist", "Avenroyth" and "Averroysta". Little

2889-491: Is any movement of a body that is not affected by forces of electrical, magnetic, or other origin, but that is only under the influence of gravitational masses. Physically speaking, this happens to be exactly what a properly functioning three-axis accelerometer is indicating when it does not detect any proper acceleration . The term inertia comes from the Latin word iners , meaning idle or sluggish. A quantity related to inertia

2996-456: Is known about Averroes's early life. Muhammad ibn Ahmad ibn Muhammad ibn Rushd was born on 14 April 1126 (520 AH ) in Córdoba . His family was well known in the city for their public service, especially in the legal and religious fields. He was probably of Muladí and Berber ancestry. His grandfather Abu al-Walid Muhammad (d. 1126) was the chief judge ( qadi ) of Córdoba and the imam of

3103-519: Is necessary for those not amenable to persuasion, e.g. enemies of the state. Therefore, he justifies war as a last resort, which he also supports using Quranic arguments. Consequently, he argues that a ruler should have both wisdom and courage, which are needed for governance and defense of the state. Like Plato, Averroes calls for women to share with men in the administration of the state, including participating as soldiers, philosophers and rulers. He regrets that contemporaneous Muslim societies limited

3210-418: Is today. The principle of inertia, as formulated by Aristotle for "motions in a void", includes that a mundane object tends to resist a change in motion. The Aristotelian division of motion into mundane and celestial became increasingly problematic in the face of the conclusions of Nicolaus Copernicus in the 16th century, who argued that the Earth is never at rest, but is actually in constant motion around

3317-518: The Book of Healing by Ibn Sina , and Rebuttal of Ibn Sina's Classification of Existing Entities . Scholarly sources, including Fakhry and the Encyclopaedia of Islam , have named three works Averroes's critical writings in this area. Fasl al-Maqal ("The Decisive Treatise") is an 1178 treatise that argues for the compatibility of Islam and philosophy. Al-Kashf 'an Manahij al-Adillah ("Exposition of

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3424-560: The Colliget became a medical textbook in Europe for centuries. His other surviving titles include On Treacle , The Differences in Temperament , and Medicinal Herbs . He also wrote summaries of the works of Greek physician Galen (died c. 210) and a commentary on Avicenna 's Urjuzah fi al-Tibb ("Poem on Medicine"). Averroes served multiple tenures as judge and produced multiple works in

3531-741: The Great Mosque of Córdoba under the Almoravids . His father Abu al-Qasim Ahmad was not as celebrated as his grandfather, but was also chief judge until the Almoravids were replaced by the Almohads in 1146. According to his traditional biographers, Averroes's education was "excellent", beginning with studies in hadith (traditions of the Islamic prophet Muhammad ), fiqh ( jurisprudence ), medicine and theology. He learned Maliki jurisprudence under al-Hafiz Abu Muhammad ibn Rizq and hadith with Ibn Bashkuwal,

3638-713: The Hanbali school and the Ashʾarites. In particular, the Ashʾari scholar al-Ghazali (1058–1111) wrote The Incoherence of the Philosophers , a scathing and influential critique of the Neoplatonic philosophical tradition in the Islamic world and against the works of Avicenna in particular. Among others, Al-Ghazali charged philosophers with non-belief in Islam and sought to disprove the teaching of

3745-466: The Neoplatonist tendencies of Muslim philosophers such as Al-Farabi and Avicenna . He rejected al-Farabi's attempt to merge the ideas of Plato and Aristotle, pointing out the differences between the two, such as Aristotle's rejection of Plato's theory of ideas . He also criticized Al-Farabi's works on logic for misinterpreting its Aristotelian source. He wrote an extensive critique of Avicenna, who

3852-413: The cause of the phenomenon, rather than the phenomenon itself. However, Newton's original ideas of "innate resistive force" were ultimately problematic for a variety of reasons, and thus most physicists no longer think in these terms. As no alternate mechanism has been readily accepted, and it is now generally accepted that there may not be one that we can know, the term "inertia" has come to mean simply

3959-493: The principle of relativity could only apply to inertial reference frames. To address this limitation, Einstein developed his general theory of relativity ("The Foundation of the General Theory of Relativity", 1916), which provided a theory including noninertial (accelerated) reference frames. In general relativity, the concept of inertial motion got a broader meaning. Taking into account general relativity, inertial motion

4066-631: The scholastic tradition. His writing attracted a strong circle of followers known as the Latin Averroists . Paris and Padua were major centers of Latin Averroism, and its prominent thirteenth-century leaders included Siger of Brabant and Boethius of Dacia . Authorities of the Roman Catholic Church reacted against the spread of Averroism. In 1270, the Bishop of Paris Étienne Tempier issued

4173-472: The spherical Earth . Averroes was aware that Arabic and Andalusian astronomers of his time focused on "mathematical" astronomy, which enabled accurate predictions through calculations but did not provide a detailed physical explanation of how the universe worked. According to him, "the astronomy of our time offers no truth, but only agrees with the calculations and not with what exists." He attempted to reform astronomy to be reconciled with physics, especially

4280-431: The "consensus of the people of Medina " argument that is one of the traditional Maliki position. In Bidāyat al-Mujtahid , one of his major contributions to the field of Islamic law, he not only describes the differences between various school of Islamic laws but also tries to theoretically explain the reasons for the difference and why they are inevitable. Even though all the schools of Islamic law are ultimately rooted in

4387-429: The "default state" of the matter was motion, not stasis (stagnation). In the 6th century, John Philoponus criticized the inconsistency between Aristotle's discussion of projectiles, where the medium keeps projectiles going, and his discussion of the void, where the medium would hinder a body's motion. Philoponus proposed that motion was not maintained by the action of a surrounding medium, but by some property imparted to

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4494-752: The "father of free thought and unbelief" and "father of rationalism". Michael Scot (1175 – c. 1232) was the first Latin translator of Averroes who translated the long commentaries of Physics , Metaphysics , On the Soul and On the Heavens , as well as multiple middle and short commentaries, starting in 1217 in Paris and Toledo . Following this, European authors such as Hermannus Alemannus , William de Luna and Armengaud of Montpellier translated Averroes's other works, sometimes with help from Jewish authors. Soon after, Averroes's works propagated among Christian scholars in

4601-520: The 11th century, Persian polymath Ibn Sina (Avicenna) claimed that a projectile in a vacuum would not stop unless acted upon. In the 14th century, Jean Buridan rejected the notion that a motion-generating property, which he named impetus , dissipated spontaneously. Buridan's position was that a moving object would be arrested by the resistance of the air and the weight of the body which would oppose its impetus. Buridan also maintained that impetus increased with speed; thus, his initial idea of impetus

4708-459: The Almohad caliph Abu Yaqub Yusuf . In a famous account reported by historian 'Abd al-Wahid al-Marrakushi , the caliph asked Averroes whether the heavens had existed since eternity or had a beginning. Knowing this question was controversial and worried a wrong answer could put him in danger, Averroes did not answer. The caliph then elaborated the views of Plato, Aristotle and Muslim philosophers on

4815-514: The Almohad empire. He also took the opportunity from his travels to conduct astronomical research. Many of his works produced between 1169 and 1179 were dated in Seville rather than Córdoba. In 1179 he was again appointed qadi in Seville. In 1182, he succeeded his friend Ibn Tufayl as court physician. Later the same year, he was appointed chief qadi of Córdoba , then controlled by the Taifa of Seville ,

4922-603: The Almoravid and the Almohad empires started as ideal, shariah-based states but then deteriorated into timocracy , oligarchy , democracy and tyranny . In his tenure as judge and jurist, Averroes for the most part ruled and gave fatwas according to the Maliki school of Islamic law which was dominant in Al-Andalus and the western Islamic world during his time. However, he frequently acted as "his own man", including sometimes rejecting

5029-434: The Latin word for "idleness" or "laziness", was not quite the same as its modern interpretation. Kepler defined inertia only in terms of resistance to movement, once again based on the axiomatic assumption that rest was a natural state which did not need explanation. It was not until the later work of Galileo and Newton unified rest and motion in one principle that the term "inertia" could be applied to those concepts as it

5136-801: The Methods of Proof"), written in 1179, criticizes the theologies of the Ash'arites , and lays out Averroes's argument for proving the existence of God, as well as his thoughts on God's attributes and actions. The 1180 Tahafut at-Tahafut ("Incoherence of the Incoherence") is a rebuttal of al-Ghazali 's (d. 1111) landmark criticism of philosophy The Incoherence of the Philosophers . It combines ideas in his commentaries and stand-alone works and uses them to respond to al-Ghazali. The work also criticizes Avicenna and his neoplatonist tendencies , sometimes agreeing with al-Ghazali's critique against him. Averroes, who served as

5243-613: The Moon are caused by variations in its thickness; the thicker parts receive more light from the Sun—and therefore emit more light—than the thinner parts. This explanation was used up to the seventeenth century by the European Scholastics to account for Galileo 's observations of spots on the Moon's surface, until the Scholastics such as Antoine Goudin in 1668 conceded that the observation

5350-471: The Moon, the Sun and the planets. He argued that those objects move uniformly in a strictly circular motion around the Earth, following Aristotelian principles. He postulates that there are three type of planetary motions; those that can be seen with the naked eye, those that requires instruments to observe and those that can only be known by philosophical reasoning. Averroes argues that the occasional opaque colors of

5457-494: The Neoplatonists of unbelief ( kufr ). Averroes responded to Al-Ghazali in his Incoherence of the Incoherence . He argued first that the differences between the two positions were not vast enough to warrant the charge of unbelief. He also said the pre-eternity doctrine did not necessarily contradict the Quran and cited verses that mention pre-existing "throne" and "water" in passages related to creation. Averroes argued that

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5564-443: The Philosophers , Judah ben Solomon ha-Kohen in his Search for Wisdom and Shem-Tov ibn Falaquera , relied heavily on Averroes's texts. In 1232, Joseph Ibn Kaspi translated Averroes's commentaries on Aristotle's Organon ; this was the first Jewish translation of a complete work. In 1260 Moses ibn Tibbon published the translation of almost all of Averroes's commentaries and some of his medical works. Jewish Averroism peaked in

5671-417: The Quran and hadith, there are "causes that necessitate differences" ( al-asbab al-lati awjabat al-ikhtilaf ). They include differences in interpreting scripture in a general or specific sense, in interpreting scriptural commands as obligatory or merely recommended, or prohibitions as discouragement or total prohibition, as well as ambiguities in the meaning of words or expressions. Averroes also writes that

5778-402: The Quran uses the rhetorical method of inviting people to the truth, which allows it to reach the common masses with its persuasiveness, whereas philosophy uses the demonstrative methods that were only available to the learned but provided the best possible understanding and knowledge. Averroes also tries to deflect Al-Ghazali's criticisms of philosophy by saying that many of them apply only to

5885-509: The Quran; the arguments from "providence" and "from invention". The providence argument considers that the world and the universe seem finely tuned to support human life . Averroes cited the sun, the moon, the rivers, the seas and the location of humans on the earth. According to him, this suggests a creator who created them for the welfare of mankind. The argument from invention contends that worldly entities such as animals and plants appear to have been invented. Therefore, Averroes argues that

5992-754: The Soul , On the Heavens , and Posterior Analytics . Averroes also wrote stand-alone philosophical treatises, including On the Intellect , On the Syllogism , On Conjunction with the Active Intellect , On Time , On the Heavenly Sphere and On the Motion of the Sphere . He also wrote several polemics : Essay on al-Farabi 's Approach to Logic, as Compared to that of Aristotle , Metaphysical Questions Dealt with in

6099-498: The Sun. Galileo , in his further development of the Copernican model , recognized these problems with the then-accepted nature of motion and, at least partially, as a result, included a restatement of Aristotle's description of motion in a void as a basic physical principle: A body moving on a level surface will continue in the same direction at a constant speed unless disturbed. Galileo writes that "all external impediments removed,

6206-696: The West, Averroes was known for his extensive commentaries on Aristotle, many of which were translated into Latin and Hebrew. The translations of his work reawakened western European interest in Aristotle and Greek thinkers, an area of study that had been widely abandoned after the fall of the Western Roman Empire . His thoughts generated controversies in Latin Christendom and triggered a philosophical movement called Averroism based on his writings. His unity of

6313-558: The ability to "light quickly on the middle term ". Averroes writes that if philosophers cannot rule—as was the case in the Almoravid and Almohad empires around his lifetime—philosophers must still try to influence the rulers towards implementing the ideal state. According to Averroes, there are two methods of teaching virtue to citizens; persuasion and coercion. Persuasion is the more natural method consisting of rhetorical, dialectical and demonstrative methods; sometimes, however, coercion

6420-465: The agent intellect gives humans the power of universal understanding, which is the material intellect. Once the person has sufficient empirical encounters with a certain concept, the power activates and gives the person universal knowledge (see also logical induction ). In his last commentary—called the Long Commentary —he proposes another theory, which becomes known as the theory of "the unity of

6527-472: The application of qiyas (reasoning by analogy) could give rise to different legal opinion because jurists might disagree on the applicability of certain analogies and different analogies might contradict each other. As did Avempace and Ibn Tufail , Averroes criticizes the Ptolemaic system using philosophical arguments and rejects the use of eccentrics and epicycles to explain the apparent motions of

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6634-570: The attribute of knowledge and argues that divine knowledge differs from human knowledge because God knows the universe because God is its cause while humans only know the universe through its effects. Averroes argues that the attribute of life can be inferred because it is the precondition of knowledge and also because God willed objects into being. Power can be inferred by God's ability to bring creations into existence. Averroes also argues that knowledge and power inevitably give rise to speech. Regarding vision and speech, he says that because God created

6741-750: The axis of rotation. Averroes Ibn Rushd ( Arabic : ابن رشد ; full name in Arabic : أبو الوليد محمد بن أحمد بن رشد , romanized :  Abū al-Walīd Muḥammad ibn Aḥmad ibn Rushd ; 14 April 1126 – 11 December 1198), often Latinized as Averroes ( English: / ə ˈ v ɛr oʊ iː z / ), was an Andalusian polymath and jurist who wrote about many subjects, including philosophy , theology , medicine , astronomy , physics , psychology , mathematics , Islamic jurisprudence and law , and linguistics . The author of more than 100 books and treatises, his philosophical works include numerous commentaries on Aristotle , for which he

6848-610: The caliph complained to Ibn Tufayl about the difficulty of understanding Aristotle's work, Ibn Tufayl recommended to the caliph that Averroes work on explaining it. This was the beginning of Averroes's massive commentaries on Aristotle; his first works on the subject were written in 1169. In the same year, Averroes was appointed qadi (judge) in Seville. In 1171 he became qadi in his hometown of Córdoba. As qadi he would decide cases and give fatwa s (legal opinions) based on religious law . The writing rate increased during this time despite other obligations and his travels within

6955-436: The context of some of Aristotle's astronomical works. However, his works influenced astronomer Nur ad-Din al-Bitruji (d. 1204) who adopted most of his reform principles and did succeed in proposing an early astronomical system based on Aristotelian physics. In physics, Averroes did not adopt the inductive method that was being developed by Al-Biruni in the Islamic world and is closer to today's physics. Rather, he was—in

7062-401: The continued motion of projectiles, after being separated from their projector, as an (itself unexplained) action of the surrounding medium continuing to move the projectile. Despite its general acceptance, Aristotle's concept of motion was disputed on several occasions by notable philosophers over nearly two millennia . For example, Lucretius (following, presumably, Epicurus ) stated that

7169-616: The contradiction. This interpretation must be done by those "rooted in knowledge"—a phrase taken from surah Āl Imrān 3 :7 of the Quran , which for Averroes refers to philosophers who during his lifetime had access to the "highest methods of knowledge". He also argues that the Quran calls for Muslims to study philosophy because the study and reflection of nature would increase a person's knowledge of "the Artisan" (God). He quotes Quranic passages calling Muslims to reflect on nature. He uses them to render

7276-559: The detailed critique by Aquinas weakened the spread of Averroism in Latin Christendom , though it maintained a following until the sixteenth century, when European thought began to diverge from Aristotelianism. Leading Averroists in the following centuries included John of Jandun and Marsilius of Padua (fourteenth century), Gaetano da Thiene and Pietro Pomponazzi (fifteenth century), and Agostino Nifo and Marcantonio Zimara (sixteenth century). Averroes had no major influence on Islamic philosophic thought until modern times. Part of

7383-651: The difference between a moving object and a stationary one without some outside reference to compare it against. This observation ultimately came to be the basis for Albert Einstein to develop the theory of special relativity . Concepts of inertia in Galileo's writings would later come to be refined, modified, and codified by Isaac Newton as the first of his laws of motion (first published in Newton's work, Philosophiæ Naturalis Principia Mathematica , in 1687): Every body perseveres in its state of rest, or of uniform motion in

7490-514: The difficulty of understanding Aristotle's original texts and to help others in a similar position. The long commentaries ( tafsir or sharh ), or line-by-line commentaries, include the complete text of the original works with a detailed analysis of each line. The long commentaries are very detailed and contain a high degree of original thought, and were unlikely to be intended for a general audience. Only five of Aristotle's works had all three types of commentaries: Physics , Metaphysics , On

7597-411: The effects of friction and air resistance , both of which tend to decrease the speed of moving objects (commonly to the point of rest). This misled the philosopher Aristotle to believe that objects would move only as long as force was applied to them. Aristotle said that all moving objects (on Earth) eventually come to rest unless an external power (force) continued to move them. Aristotle explained

7704-611: The existence of God as the Necessary Existent. Averroes felt strongly about the incorporation of Greek thought into the Muslim world , and wrote that "if before us someone has inquired into [wisdom], it behooves us to seek help from what he has said. It is irrelevant whether he belongs to our community or to another". During Averroes's lifetime, philosophy came under attack from the Sunni tradition , especially from theological schools like

7811-553: The fields of Islamic jurisprudence or legal theory. The only book that survives today is Bidāyat al-Mujtahid wa Nihāyat al-Muqtaṣid ("Primer of the Discretionary Scholar"). In this work he explains the differences of opinion ( ikhtilaf ) between the Sunni madhhabs (schools of Islamic jurisprudence) both in practice and in their underlying juristic principles, as well as the reason why they are inevitable. Despite his status as

7918-435: The first of the three works, Averroes follows Ibn Bajja 's theory that something called the " material intellect " stores specific images that a person encounters. These images serve as basis for the "unification" by the universal " agent intellect ", which, once it happens, allow a person to gain universal knowledge about that concept. In his middle commentary, Averroes moves towards the ideas of Al-Farabi and Avicenna, saying

8025-536: The fourteenth century; Jewish writers of this time who translated or were influenced by Averroes include Kalonymus ben Kalonymus of Arles , France, Todros Todrosi of Arles, Elia del Medigo of Candia and Gersonides of Languedoc . Averroes's main influence on the Christian West was through his extensive commentaries on Aristotle. After the fall of the Western Roman Empire , western Europe fell into

8132-486: The growing theory of impetus to involve linear motion alone: [Any] portion of corporeal matter which moves by itself when an impetus has been impressed on it by any external motive force has a natural tendency to move on a rectilinear, not a curved, path. Benedetti cites the motion of a rock in a sling as an example of the inherent linear motion of objects, forced into circular motion. According to science historian Charles Coulston Gillispie , inertia "entered science as

8239-531: The ideal state to be one based on the Islamic law ( shariah ). His interpretation of Plato's philosopher-king followed that of Al-Farabi, which equates the philosopher-king with the imam , caliph and lawgiver of the state. Averroes's description of the characteristics of a philosopher-king are similar to those given by Al-Farabi; they include love of knowledge, good memory, love of learning, love of truth, dislike for sensual pleasures, dislike for amassing wealth, magnanimity, courage, steadfastness, eloquence and

8346-488: The intellect thesis, proposing that all humans share the same intellect, became one of the best-known and most controversial Averroist doctrines in the West. His works were condemned by the Catholic Church in 1270 and 1277. Although weakened by condemnations and sustained critique from Thomas Aquinas , Latin Averroism continued to attract followers up to the sixteenth century. Ibn Rushd's full, transliterated Arabic name

8453-452: The intellect ". In it, Averroes argues that there is only one material intellect, which is the same for all humans and is unmixed with human body. To explain how different individuals can have different thoughts, he uses a concept he calls fikr —known as cogitatio in Latin—a process that happens in human brains and contains not universal knowledge but "active consideration of particular things"

8560-425: The light from the humors of the eye [the lens], just like the humors receive the light from air." Another of his departure from Galen and the medical theories of the time is his description of stroke as produced by the brain and caused by an obstruction of the arteries from the heart to the brain. This explanation is closer to the modern understanding of the disease compared to that of Galen, which attributes it to

8667-509: The object when it was set in motion. Although this was not the modern concept of inertia, for there was still the need for a power to keep a body in motion, it proved a fundamental step in that direction. This view was strongly opposed by Averroes and by many scholastic philosophers who supported Aristotle. However, this view did not go unchallenged in the Islamic world , where Philoponus had several supporters who further developed his ideas. In

8774-518: The obstruction between heart and the periphery. He was also the first to describe the signs and symptoms of Parkinson's disease in his Kulliyat , although he did not give the disease a name. Maimonides (d. 1204) was among early Jewish scholars who received Averroes's works enthusiastically, saying he "received lately everything Averroes had written on the works of Aristotle" and that Averroes "was extremely right". Thirteenth-century Jewish writers, including Samuel ibn Tibbon in his work Opinion of

8881-607: The person has encountered. This theory attracted controversy when Averroes's works entered Christian Europe; in 1229 Thomas Aquinas wrote a detailed critique titled On the Unity of the Intellect against the Averroists . While his works in medicine indicate an in-depth theoretical knowledge in medicine of his time, he likely had limited expertise as a practitioner, and declared in one of his works that he had not "practiced much apart from myself, my relatives or my friends." He did serve as

8988-460: The phenomenon itself, rather than any inherent mechanism. Thus, ultimately, "inertia" in modern classical physics has come to be a name for the same phenomenon as described by Newton's first law of motion, and the two concepts are now considered to be equivalent. Albert Einstein 's theory of special relativity , as proposed in his 1905 paper entitled " On the Electrodynamics of Moving Bodies ",

9095-526: The philosophers using logical arguments. In Decisive Treatise , Averroes argues that philosophy—which for him represented conclusions reached using reason and careful method—cannot contradict revelations in Islam because they are just two different methods of reaching the truth, and "truth cannot contradict truth". When conclusions reached by philosophy appear to contradict the text of the revelation, then according to Averroes, revelation must be subjected to interpretation or allegorical understanding to remove

9202-788: The philosophy of Avicenna and not to that of Aristotle, which Averroes argues to be the true philosophy from which Avicenna has deviated. Averroes lays out his views on the existence and nature of God in the treatise The Exposition of the Methods of Proof . He examines and critiques the doctrines of four sects of Islam: the Asharites , the Mutazilites , the Sufis and those he calls the "literalists" ( al-hashwiyah ). Among other things, he examines their proofs of God's existence and critiques each one. Averroes argues that there are two arguments for God's existence that he deems logically sound and in accordance to

9309-405: The physics of Aristotle. His long commentary of Aristotle's Metaphysics describes the principles of his attempted reform, but later in his life he declared that his attempts had failed. He confessed that he had not enough time or knowledge to reconcile the observed planetary motions with Aristotelian principles. In addition, he did not know the works of Eudoxus and Callippus , and so he missed

9416-510: The public role of women; he says this limitation is harmful to the state's well-being. Averroes also accepted Plato's ideas of the deterioration of the ideal state. He cites examples from Islamic history when the Rashidun caliphate —which in Sunni tradition represented the ideal state led by "rightly guided caliphs"—became a dynastic state under Muawiyah , founder of the Umayyad dynasty . He also says

9523-518: The reason was geography; Averroes lived in Spain, the extreme west of the Islamic civilization far from the centers of Islamic intellectual traditions. Also, his philosophy may not have appealed to Islamic scholars of his time. His focus on Aristotle's works was outdated in the twelfth-century Muslim world, which had already scrutinized Aristotle since the ninth century and by now was engaging deeply with newer schools of thought, especially that of Avicenna. In

9630-427: The retina: he might have been the first to recognize that retina was the part of the eye responsible for sensing light, rather than the lens as was commonly thought. Modern scholars dispute whether this is what he meant it his Kulliyat , but Averroes also stated a similar observation in his commentary to Aristotle's Sense and Sensibilia : "the innermost of the coats of the eye [the retina] must necessarily receive

9737-495: The royal physician at the Almohad court, wrote a number of medical treatises. The most famous was al-Kulliyat fi al-Tibb ("The General Principles of Medicine", Latinized in the west as the Colliget ), written around 1162, before his appointment at court. The title of this book is the opposite of al-Juz'iyyat fi al-Tibb ("The Specificities of Medicine"), written by his friend Ibn Zuhr, and the two collaborated intending that their works complement each other. The Latin translation of

9844-457: The signs and symptoms of Parkinson's disease for the first time, and might have been the first to identify the retina as the part of the eye responsible for sensing light. His medical book Al-Kulliyat fi al-Tibb , translated into Latin and known as the Colliget , became a textbook in Europe for centuries. His legacy in the Islamic world was modest for geographical and intellectual reasons. In

9951-454: The topic and discussed them with Ibn Tufayl. This display of knowledge put Averroes at ease; Averroes then explained his views on the subject, which impressed the caliph. Averroes was similarly impressed by Abu Yaqub and later said the caliph had "a profuseness of learning I did not suspect". After their introduction, Averroes remained in Abu Yaqub's favor until the caliph died in 1184. When

10058-406: The west and are important to the overall development of physics. Averroes expounds his thoughts on psychology in his three commentaries on Aristotle's On the Soul . Averroes is interested in explaining the human intellect using philosophical methods and by interpreting Aristotle's ideas. His position on the topic changed throughout his career as his thoughts developed. In his short commentary,

10165-509: The wheel's balance spring for adjusting the watch's rate, so the collets are used for adjusting both poise and rate. Swiss patents were granted to Patek Phillipe for the Gyromax balance on May 15, 1949 and December 31, 1951, and the balance was first used in watches in 1952. Another balance wheel with a similar design is the Rolex Microstella. Inertia LAW I. Every object perseveres in its state of rest, or of uniform motion in

10272-412: The wheel's moment of inertia, increasing its speed. When the collet's cutout points toward the center, the weight moves outward and the balance wheel turns more slowly. A watchmaker can turn an individual collet to adjust the wheel's balance, referred to as 'poise', or pairs of opposing collets to adjust the wheel's rotation speed. The Gyromax is a 'free sprung' balance, meaning there is no regulator on

10379-485: The words of historian of science Ruth Glasner—an "exegetical" scientist who produced new theses about nature through discussions of previous texts, especially the writings of Aristotle. because of this approach, he was often depicted as an unimaginative follower of Aristotle, but Glasner argues that Averroes's work introduced highly original theories of physics, especially his elaboration of Aristotle's minima naturalia and on motion as forma fluens , which were taken up in

10486-428: The world was created at a specific moment in time or whether it has always existed . Neo-Platonic philosophers such as Al-Farabi and Avicenna argued the world has always existed. This view was criticized by the mutakallimin (philosophers and theologians) of the Ashʾari tradition; in particular, al-Ghazali wrote an extensive refutation of the pre-eternity doctrine in his The Incoherence of the Philosophers and accused

10593-435: The world, he necessarily knows every part of it in the same way an artist understands his or her work intimately. Because two elements of the world are the visual and the auditory, God must necessarily possess vision and speech. The omnipotence paradox was first addressed by Averroes and only later by Thomas Aquinas . In the centuries preceding Averroes, there had been a debate between Muslim thinkers questioning whether

10700-404: Was built on the understanding of inertial reference frames developed by Galileo, Huygens and Newton. While this revolutionary theory did significantly change the meaning of many Newtonian concepts such as mass , energy , and distance , Einstein's concept of inertia remained at first unchanged from Newton's original meaning. However, this resulted in a limitation inherent in special relativity:

10807-603: Was especially competent in the field of khilaf (disputes and controversies in the Islamic jurisprudence). Ibn al-Abbar also mentioned his interests in "the sciences of the ancients", probably in reference to Greek philosophy and sciences. By 1153 Averroes was in Marrakesh , the capital of the Almohad Caliphate (now in Morocco), to perform astronomical observations and to support the Almohad project of building new colleges. He

10914-451: Was hoping to find physical laws of astronomical movements instead of only the mathematical laws known at the time but this research was unsuccessful. During his stay in Marrakesh, he likely met ibn Tufayl, a renowned philosopher and the author of Hayy ibn Yaqdhan who was also the court physician in Marrakesh. Averroes and ibn Tufayl became friends despite the differences in their philosophies. In 1169, ibn Tufayl introduced Averroes to

11021-514: Was known in the Western world as The Commentator and Father of Rationalism . Averroes was a strong proponent of Aristotelianism ; he attempted to restore what he considered the original teachings of Aristotle and opposed the Neoplatonist tendencies of earlier Muslim thinkers, such as Al-Farabi and Avicenna . He also defended the pursuit of philosophy against criticism by Ashari theologians such as Al-Ghazali . Averroes argued that philosophy

11128-416: Was more likely caused by mountains on the Moon. He and Ibn Bajja observed sunspots , which they thought were transits of Venus and Mercury between the Sun and the Earth. In 1153 he conducted astronomical observations in Marrakesh, where he observed the star Canopus (Arabic: Suhayl ) which was invisible in the latitude of his native Spain. He used this observation to support Aristotle's argument for

11235-481: Was permissible in Islam and even compulsory among certain elites. He also argued scriptural text should be interpreted allegorically if it appeared to contradict conclusions reached by reason and philosophy. In Islamic jurisprudence, he wrote the Bidāyat al-Mujtahid on the differences between Islamic schools of law and the principles that caused their differences. In medicine, he proposed a new theory of stroke , described

11342-509: Was similar in many ways to the modern concept of momentum. Despite the obvious similarities to more modern ideas of inertia, Buridan saw his theory as only a modification to Aristotle's basic philosophy, maintaining many other peripatetic views, including the belief that there was still a fundamental difference between an object in motion and an object at rest. Buridan also believed that impetus could be not only linear but also circular in nature, causing objects (such as celestial bodies) to move in

11449-509: Was the standard-bearer of Islamic Neoplatonism in the Middle Ages. He argued that Avicenna's theory of emanation had many fallacies and was not found in the works of Aristotle. Averroes disagreed with Avicenna's view that existence is merely an accident added to essence, arguing the reverse; something exists per se and essence can only be found by subsequent abstraction. He also rejected Avicenna's modality and Avicenna's argument to prove

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