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The Canon of Medicine
The Book of Healing
Hayy ibn Yaqdhan
Criticism of Avicennian philosophy
Unani medicine

The Book of Healing (Arabic: کتاب الشفاء Kitab Al-Shifaʾ, Latin: Sanatio) is a scientific and philosophical encyclopedia written by the Persian polymath Abū Alī ibn Sīnā (Avicenna) from Asfahana, near Bukhara in Greater Persia. Despite its English title, it is not in fact mainly concerned with medicine: the Latin title Sanatio is a mistranslation of Shifa, which, even though it means 'healing', has the secondary meaning of "satiation", "completion", or "wholeness", the meaning most-likely intended by Ibn Sīnā. (Note that, in English, the words, "whole" and "healthy" are semantically related.)

This book is Ibn Sina’s major work on science and philosophy. He probably began to compose the al-Shifa in 1014, completed it around 1020,[1] and published it in 1027.[2]

The book covers nine volumes on Avicennian logic; eight on the natural sciences (including Earth science, Islamic geography and Islamic physics); four on the quadrivium of arithmetic, geometry, astronomy, and music; and the remaining volumes on Avicennian philosophy, metaphysics and psychology.[2] It is further subdivided into categories such as Islamic ethics and politics. It was influenced by ancient Greek philosophers, such as Aristotle, Hellenistic thinkers such as Ptolemy, earlier Persian and Muslim scientists, and philosophers such as Al-Kindi (Alkindus), Al-Farabi (Alfarabi) and Abū Rayhān al-Bīrūnī.



In astronomy, the book proposed the theory that Venus is closer to Earth than the Sun. The study of astrology was rejected by Avicenna. His reasons were that the methods used by astrologers were conjectural rather than empirical, and that the views of astrologers conflicted with orthodox Islam. He also cited passages from the Qur'an in order to justify his denunciation of astrology on both scientific and religious grounds.[3]

Celestial mechanics

See also: Celestial spheres

In celestial mechanics, the first millennium had seen the Hipparchan innovation in Aristotelian dynamics with its supplementary theory of applied force. Hipparchus described a self-dissipating force or impetus, to explain the sublunar phenomenon of detached violent motion, such as the flight of projectiles counter to the force of gravity. (John Philoponus had also applied this concept to celestial motion.) The second millennium then saw a radically-different theory of impetus, an essentially self-conserving impetus, developed by Avicenna and, later, Jean Buridan, which was also applied to celestial motion.

In the fourteenth century, the logician and natural philosopher, Jean Buridan, rector of Paris University, subscribed to the Avicennan variant of impetus dynamics according to which impetus is conserved forever in the absence of any resistance to motion, rather than being evanescent and self-decaying as in the Hipparchan variant. In order to dispense with the need for positing continually moving intelligences or souls in the celestial spheres, which he pointed out are not posited by the Bible, Buridan applied the Avicennan self-conserving impetus theory to their endless rotation by extension of a terrestrial example of its application to rotary motion in the form of a rotating millwheel that continues rotating for a long time after the originally propelling hand is withdrawn, driven by the impetus applied to it.[4]


Ibn Sina's theory on the formation of metals combined Jābir ibn Hayyān's sulfur-mercury theory from Islamic alchemy (although he was critic of alchemy) with the mineralogical theories of Aristotle and Theophrastus. He created a synthesis of ideas concerning the nature of the mineral and metallic states.[5]

Earth sciences

Ibn Sina made significant contributions to natural sciences (which he called Attabieyat), particularly in Earth sciences such as Islamic geography and geology. Part 2, Section 5, of The Book of Healing, contains his essay on mineralogy and meteorology, in six chapters: formation of mountains; the advantages of mountains in the formation of clouds; sources of water; origin of earthquakes; formation of minerals; and the diversity of earth’s terrain. These principles were later known in the Renaissance of Europe as the law of superposition of strata, the concept of catastrophism, and the doctrine of uniformitarianism. These concepts were also embodied in the Theory of the Earth by James Hutton in the Eighteenth century C.E. Academics such as Toulmin and Goodfield (1965), commented on Avicenna's contribution: "Around A.D. 1000, Avicenna was already suggesting a hypothesis about the origin of mountain ranges, which in the Christian world, would still have been considered quite radical eight hundred years later".[6] Avicenna's scientific methodology of field observation was also original in the Earth sciences, and remains an essential part of modern geological investigations.[7]

In natural history, The Book of Healing was the first book to treat the three kingdoms (the mineral, vegetable and animal kingdoms) together systematically, and it contains the most extensive medieval discussion on geology and the mineral kingdom. It describes the structure of a meteor, dealt with the formation of sedimentary rocks, and the role of earthquakes in mountain formation. Ibn Sina also displays a clear awareness of the possibility of seas turning into dry land and vice-versa, and therefore provides a correct explanation for the discovery of fossils on mountain tops.[5]


In contrast to ancient writers such as Pythagoras, Ovid and Seneca the Younger who asserted that mountains were caused due to reasons such as subterranean winds and volcanic eruptions, Ibn Sina was the first to emphasize the role of sedimentary and erosive phenomena in the formation of mountains. This had an influence on later writings by Restoro d'Arezzo, Leonardo da Vinci and René Descartes on the subject.[8] The Book of Healing hypothesized on two causes of mountains:

"Either they are the effects of upheavals of the crust of the earth, such as might occur during a violent earthquake, or they are the effect of water, which, cutting itself a new route, has denuded the valleys, the strata being of different kinds, some soft, some hard... It would require a long period of time for all such changes to be accomplished, during which the mountains themselves might be somewhat diminished in size."[6]

Ibn Sina further elaborated on the causes of mountains. He was aware of the ability of certain springs to petrify objects and thus envisaged the concept of a 'mineralizing and petrifying virtue' in the Earth. He wrote that valleys had been excavated by the action of currents of water, and that mountains themselves were formed by petrification of 'agglutinative clay' after land was exposed by the retreat of the sea, citing fossil shells found inland as evidence. He wrote that currently mountains are chiefly decaying and disintegrating but that their layered appearance indicates that they were formerly produced by a sedimentary process, implying a cycle in the formation and decomposition of mountains.[9]

The concept of uniformitarianism in geological processes can be traced back to Ibn Sina's The Book of Healing. He recognized that mountains were formed after a long sequence of events that predate human existence. While discussing the origins of mountains in The Book of Healing, Ibn Sina was also the first to outline one of the principles underlying geologic time scales, the law of superposition of strata:[7]

"It is also possible that the sea may have happened to flow little by little over the land consisting of both plain and mountain, and then have ebbed away from it. ... It is possible that each time the land was exposed by the ebbing of the sea a layer was left, since we see that some mountains appear to have been piled up layer by layer, and it is therefore likely that the clay from which they were formed was itself at one time arranged in layers. One layer was formed first, then at a different period, a further was formed and piled, upon the first, and so on. Over each layer there spread a substance of different material, which formed a partition between it and the next layer; but when petrification took place something occurred to the partition which caused it to break up and disintegrate from between the layers (possibly referring to unconformity). ... As to the beginning of the sea, its clay is either sedimentary or primeval, the latter not being sedimentary. It is probable that the sedimantary clay was formed by the disintegration of the strata of mountains. Such is the formation of mountains."

Avicenna's theories on the formation of stones also added considerably to ideas about the Earth from a 'proto-chemical' point of view. For example, his classification of minerals into salts, sulphurs, metals and stones remained in use until the end of the 18th century. He classified minerals as follows:[10]

  • Minerals
    • 'Weak in substance and feeble in composition and union'
      • Soluble (salts)
      • Insoluble and oily (sulphurs)
    • 'Strong in substance'
      • Malleable (fusible substances or metals)
      • Non-malleable (stones)

Due to his fundamental contributions to the development of geology, partciularly regarding the origins of mountains, Avicenna is considered fully entitled to be called the 'Father of Geology'.[11]


Ibn Sina also contributed to paleontology with his explanation of how the stoniness of fossils was caused. Aristotle previously explained it in terms of vaporous exhalations, which Ibn Sina modified into the theory of petrifying fluids (succus lapidificatus), which was elaborated on by Albert of Saxony in the 14th century and accepted in some form by most naturalists by the 16th century.[12] Ibn Sina gave the following explanation for the origin of fossils from the petrifaction of plants and animals:

"If what is said concerning the petrifaction of animals and plants is true, the cause of this (phenomenon) is a powerful mineralizing and petrifying virtue which arises in certain stony spots, or emanates suddenly from the earth during earthquake and subsidences, and petrifies whatever comes into contact with it. As a matter of fact, the petrifaction of the bodies of plants and animals is not more extraordinary than the transformation of waters."[7]


See also: Avicennian physics, Theory of impetus, and Physics in medieval Islam

In optics, Ibn Sina discovered that the speed of light is finite, as he "observed that if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite."[13] He also provided a sophisticated explanation for the rainbow phenomenon. Carl Benjamin Boyer described Ibn Sīnā's theory on the rainbow as follows:

"Independent observation had demonstrated to him that the bow is not formed in the dark cloud but rather in the very thin mist lying between the cloud and the sun or observer. The cloud, he thought, serves simply as the background of this thin substance, much as a quicksilver lining is placed upon the rear surface of the glass in a mirror. Ibn Sīnā would change the place not only of the bow, but also of the color formation, holding the iridescence to be merely a subjective sensation in the eye."[14]

In mechanics, Ibn Sīnā developed an elaborate theory of motion, in which he made a distinction between the inclination and force of a projectile, and concluded that motion was a result of an inclination (mayl) transferred to the projectile by the thrower, and that projectile motion in a vacuum would not cease.[15] This was the first alternative to the Aristotelian theory.[16] In the Avicennan theory of motion, the violent inclination he conceived was non-self-consuming, a permanent force whose effect was dissipated only as a result of external agents such as air resistance,[15][16] making him "the first to conceive such a permanent type of impressed virtue for non-natural motion." Such a self-motion (mayl) is "almost the opposite of the Aristotelian conception of violent motion of the projectile type, and it is rather reminiscent of the principle of inertia, i.e., Newton's first law of motion."[16] His theory of mayl also attempted to provide a quantitive relation between the weight and velocity of a moving body,[17] for which he is considered a pioneer of the concept of momentum.[18][19] His theory of motion later formed the basis of Jean Buridan's theory of impetus and exerted an influence on the work of Galileo Galilei.[20]


See also: Avicennism and The Canon of Medicine

In The Book of Healing, Avicenna discussed the mind, its existence, the mind and body relationship, sensation, perception, etc. He wrote that at the most common level, the influence of the mind on the body can be seen in voluntary movements, in that the body obeys whenever the mind wishes to move the body. He further writes that the second level of influence of the mind on the body is from emotions and the will. As an example, he states that if a plank of wood is placed as a bridge over a chasm, a person could hardly creep over it without falling if that person only pictures himself/herself in a possible fall so vividly that the "natural power of limbs accord with it." He also writes that strong negative emotions can have a negative effect on the vegetative functions of an individual and may even lead to death in some cases. He also discusses hypnosis (al Wahm al-Amil), stating that one could create conditions in another person so that he/she accepts the reality of hypnosis. Avicenna was also the first to divide human perception into the five external senses (the classical senses of hearing, sight, smell, taste and touch known since antiquity) and the five internal senses which he discovered himself. The five internal senses he discovered were: the sensus communis (seat of all senses) which integrates sense data into percepts; the imaginative faculty which conserves the perceptual images; the sense of imagination which acts upon these images by combining and separating them, serving as the seat of the practical intellect; Wahm (instinct) which perceives qualities (such as good and bad, love and hate, etc.) and forms the basis of a person's character whether or not influenced by reason; and intentions (ma'ni) which conserve all these notions in memory.[21]

Avicenna also gave psychological explanations for certain somatic illnesses, and he always linked the physical and psychological illnesses together. He described melancholia (depression) as a type of mood disorder in which the person may become suspicious and develop certain types of phobias. He stated that anger heralded the transition of melancholia to mania, and explained that humidity inside the head can contribute to mood disorders. He recognized that this occurs when the amount of breath changes: happiness increases the breath, which leads to increased moisture inside the brain, but if this moisture goes beyond its limits, the brain would lose control over its rationality and lead to mental disorders. He also wrote about symptoms and treatments for nightmare, epilepsy, and weak memory.[22]

Avicenna often used psychological methods to treat his patients.[22] One such example is when a prince of Persia had melancholia and suffered from the delusion that he is a cow, and who would low like a cow crying "Kill me so that a good stew may be made of my flesh" and would never eat anything. Avicenna was persuaded to the case and sent a message to the patient, asking him to be happy as the butcher was coming to slaughter him, and the sick man rejoiced. When Avicenna approached the prince with a knife in his hand, he asked "where is the cow so I may kill it." The patient then lowed like a cow to indicate where he was. "By order of the butcher, the patient was also laid on the ground for slaughter." When Avicenna approached the patient pretending to slaughter him, he said, "the cow is too lean and not ready to be killed. He must be fed properly and I will kill it when it becomes healthy and fat." The patient was then offered food which he ate eagerly and gradually "gained strength, got rid of his delusion, and was completely cured."[23]


Main article: Avicennism

In the medieval Islamic world, due to Avicenna's successful reconciliation of Aristotelianism and Neoplatonism along with Kalam, Avicennism eventually became the leading school of early Islamic philosophy by the 12th century, with Avicenna becoming a central authority on philosophy.[24]

Avicennism was also influential in medieval Europe, particular his doctrines on the nature of the soul and his existence-essence distinction, along with the debates and censure that they raised in scholastic Europe. This was particularly the case in Paris, where Avicennism was later proscribed in 1210. Nevertheless, his Muslim psychology and theory of knowledge influenced William of Auvergne and Albertus Magnus, while his metaphysics had an impact on the thought of Thomas Aquinas.[25]


Avicenna discussed the topic of logic in Islamic philosophy extensively in his works, and developed his own system of logic known as "Avicennian logic" as an alternative to Aristotelian logic. By the 12th century, Avicennian logic had replaced Aristotelian logic as the dominant system of logic in the Islamic world.[26] After the Latin translations of the 12th century, his writings on logic were also an important influence on Western medieval writers such as Albertus Magnus.[27]

He wrote on the hypothetical syllogism[2] and on the propositional calculus, which were both part of the Stoic logical tradition.[28] He developed an original theory of “temporally modalized” syllogistic[29] and made use of inductive logic, such as the methods of agreement, difference and concomitant variation which are critical to the scientific method.[2]


Early Islamic metaphysics, imbued as it is with Islamic theology, distinguishes more clearly than Aristotelianism the difference between essence and existence. Whereas existence is the domain of the contingent and the accidental, essence endures within a being beyond the accidental. The philosophy of Ibn Sīnā, particularly that part relating to metaphysics, owes much to al-Farabi. The search for a truly definitive Islamic philosophy can be seen in what is left to us of his work.

Following al-Farabi's lead, Avicenna initiated a full-fledged inquiry into the question of being, in which he distinguished between essence (Mahiat) and existence (Wujud). He argued that the fact of existence can not be inferred from or accounted for by the essence of existing things and that form and matter by themselves cannot interact and originate the movement of the universe or the progressive actualization of existing things. Existence must, therefore, be due to an agent-cause that necessitates, imparts, gives, or adds existence to an essence. To do so, the cause must be an existing thing and coexist with its effect. [30]

Avicenna's proof for the existence of God was the first ontological argument, which he proposed in the Metaphysics section of The Book of Healing.[31][32] This was the first attempt at using the method of a priori proof, which utilizes intuition and reason alone. Avicenna's proof of God's existence is unique in that it can be classified as both a cosmological argument and an ontological argument. "It is ontological insofar as ‘necessary existence’ in intellect is the first basis for arguing for a Necessary Existent". The proof is also "cosmological insofar as most of it is taken up with arguing that contingent existents cannot stand alone and must end up in a Necessary Existent."[33]

Philosophy of science

In the Al-Burhan (On Demonstration) section of the book, Avicenna discussed the philosophy of science and described an early scientific method of inquiry. He discusses Aristotle's Posterior Analytics and significantly diverged from it on several points. Avicenna discussed the issue of a proper methodology for scientific inquiry and the question of "How does one acquire the first principles of a science?" He asked how a scientist would arrive at "the initial axioms or hypotheses of a deductive science without inferring them from some more basic premises?" He explains that the ideal situation is when one grasps that a "relation holds between the terms, which would allow for absolute, universal certainty." Avicenna then adds two further methods for arriving at the first principles: the ancient Aristotelian method of induction (istiqra), and the method of examination and experimentation (tajriba). Avicenna criticized Aristotelian induction, arguing that "it does not lead to the absolute, universal, and certain premises that it purports to provide." In its place, he develops a "method of experimentation as a means for scientific inquiry."[34]

Sections of the text

Critical editions of the Arabic text have been published in Cairo, 1952-83, originally under the supervision of Ibrahim Madkour; some of these editions are given below.[1]

  • Al-Mantiq (Logic), Part 1, al-Ahwani, Cairo: al-Matba’ah al-Amiriyah, 1952;
    • trans. N. Shehaby, The Propositional Logic of Ibn Sina, Dordrecht: Reidel, 1973. (Volume I, Part 1 of al-Shifa’.)
  • Al-‘Ibarah (Interpretation), ed. M. El-Khodeiri, Cairo: Dar al-Katib al-Arabi, 1970. (Volume 1, Part 3 of al-Shifa’.)
  • Al-Qiyas (Syllogism), ed. S. Zayed and I. Madkour, Cairo: Organisme General des Imprimeries Gouvernementales, 1964. (Volume I, Part 4 of al-Shifa’.)
  • Al-Burhan (Demonstration), ed. A.E. Affifi, Cairo: Organisme General des Imprimeries Gouvernementales, 1956. (Volume I, Part 5 of al-Shifa’.)
  • Al-Jadal (Dialectic), ed. A.F Al-Ehwany, Cairo: Organisme General des Imprimeries Gouvernementales, 1965. (Volume I, Part 7 of al-Shifa’.)
  • Al-Khatabah (Rhetoric), ed. S. Salim, Cairo: Imprimerie Nationale, 1954. (Volume I, Part 8 of al-Shifa’.)
  • Al-Ilahiyat (Theology), ed. M.Y. Moussa, S. Dunya and S. Zayed, Cairo: Organisme General des Imprimeries Gouvernementales, 1960;
    • ed. and trans. R.M. Savory and D. A. Agius, ‘Ibn Sina on Primary Concepts in the Metaphysics of al-Shifa’, in Logikos Islamikos, Toronto, Ont.: Pontifical Institute for Mediaeval Studies, 1984;
    • trans. G.C. Anawati, La metaphysique du Shifa’, Etudes Musulmanes 21, 27, Paris: Vrin, 1978, 1985. (This is the metaphysics of al-Shifa’, Volume I, Book 5.)
  • Al-Nafs (The Soul), ed. G.C. Anawati and S. Zayed, Cairo: Organisme General des Imprimeries Gouvernementales, 1975;
    • ed. F. Rahman, Avicenna’s De Anima, Being the Psychological Part of Kitab al-Shifa’, London: Oxford University Press, 1959. (Volume 1, part 6 of al-Shifa’.)

See also


  2. 2.0 2.1 2.2 2.3 Lenn Evan Goodman (1992), Avicenna, p. 31, Routledge, ISBN 041501929X. Cite error: Invalid <ref> tag; name "Goodman" defined multiple times with different content
  3. George Saliba (1994), A History of Arabic Astronomy: Planetary Theories During the Golden Age of Islam, p. 60, 67-69. New York University Press, ISBN 0814780237.
  4. According to Buridan's theory, impetus acts in the same direction or manner in which it was created; thus, a circularly or rotationally created impetus acts in a circular fashion thereafter. On Buridan's analysis, it seems that Goliath must have died of shock and amazement as David's stone continued its circular motion around David's hand after being released from the sling.
  5. 5.0 5.1 Seyyed Hossein Nasr (December 2003), "The achievements of IBN SINA in the field of science and his contributions to its philosophy", Islam & Science 1
  6. 6.0 6.1 Stephen Toulmin and June Goodfield (1965), The Ancestry of Science: The Discovery of Time, p. 64, University of Chicago Press (cf. The Contribution of Ibn Sina to the development of Earth sciences)
  7. 7.0 7.1 7.2 Munim M. Al-Rawi and Salim Al-Hassani (November 2002). "The Contribution of Ibn Sina (Avicenna) to the development of Earth sciences" (PDF). FSTC. Retrieved on 2008-07-01.
  8. Vai, Gian Battista; Caldwell, W. G. E. (2006), The origins of geology in Italy: [in memory of Nicoletta Morello, 1946-2006], Geological Society of America, p. 158, ISBN 0813724112
  9. David Roger Oldroyd (1996), Thinking about the earth: a history of ideas in geology, Harvard University Press, pp. 23-4, ISBN 0674883829
  10. David Roger Oldroyd (1996), Thinking about the earth: a history of ideas in geology, Harvard University Press, p. 23, ISBN 0674883829
  11. Medvei, Victor Cornelius (1993), The History of Clinical Endocrinology: A Comprehensive Account of Endocrinology from Earliest Times to the Present Day, Taylor and Francis, p. 46, ISBN 1850704279
  12. Rudwick, M. J. S. (1985), The Meaning of Fossils: Episodes in the History of Palaeontology, University of Chicago Press, p. 24, ISBN 0226731030
  13. George Sarton, Introduction to the History of Science, Vol. 1, p. 710.
  14. Carl Benjamin Boyer (1954). "Robert Grosseteste on the Rainbow", Osiris 11, p. 247-258 [248].
  15. 15.0 15.1 Fernando Espinoza (2005). "An analysis of the historical development of ideas about motion and its implications for teaching", Physics Education 40 (2), p. 141.
  16. 16.0 16.1 16.2 Aydin Sayili (1987), "Ibn Sīnā and Buridan on the Motion of the Projectile", Annals of the New York Academy of Sciences 500 (1): 477–482 [477]:
    Ibn Sina adopted this idea in its rough outline, but the violent inclination as he conceived it was a non-self-consuming one. It was a permanent force whose effect got dissipated only as a result of external agents such as air resistance. He is apparently the first to conceive such a permanent type of impressed virtue for non-natural motion. [...] Indeed, self-motion of the type conceived by Ibn Sina is almost the opposite of the Aristotelian conception of violent motion of the projectile type, and it is rather reminiscent of the principle of inertia, i.e., Newton's first law of motion.
  17. Seyyed Hossein Nasr & Mehdi Amin Razavi (1996), The Islamic intellectual tradition in Persia, Routledge, p. 72, ISBN 0700703144
  18. Seyyed Hossein Nasr, "Islamic Conception Of Intellectual Life", in Philip P. Wiener (ed.), Dictionary of the History of Ideas, Vol. 2, p. 65, Charles Scribner's Sons, New York, 1973-1974.
  19. Seyyed Hossein Nasr & Mehdi Amin Razavi (1996), The Islamic intellectual tradition in Persia, Routledge, p. 72, ISBN 0700703144
  20. A. Sayili (1987), "Ibn Sīnā and Buridan on the Motion of the Projectile", Annals of the New York Academy of Sciences 500 (1), pp. 477–482
  21. Amber Haque (2004), "Psychology from Islamic Perspective: Contributions of Early Muslim Scholars and Challenges to Contemporary Muslim Psychologists", Journal of Religion and Health 43 (4): 357-377 [366]
  22. 22.0 22.1 Amber Haque (2004), "Psychology from Islamic Perspective: Contributions of Early Muslim Scholars and Challenges to Contemporary Muslim Psychologists", Journal of Religion and Health 43 (4): 357-377 [366].
  23. Amber Haque (2004), "Psychology from Islamic Perspective: Contributions of Early Muslim Scholars and Challenges to Contemporary Muslim Psychologists", Journal of Religion and Health 43 (4): 357-377 [376].
  24. Nahyan A. G. Fancy (2006), p. 80-81, "Pulmonary Transit and Bodily Resurrection: The Interaction of Medicine, Philosophy and Religion in the Works of Ibn al-Nafīs (d. 1288)", Electronic Theses and Dissertations, University of Notre Dame.[1]
  25. The Internet Encyclopedia of Philosophy, Avicenna/Ibn Sina (CA. 980-1037)
  26. I. M. Bochenski (1961), "On the history of the history of logic", A history of formal logic, p. 4-10. Translated by I. Thomas, Notre Dame, Indiana University Press. (cf. Ancient Islamic (Arabic and Persian) Logic and Ontology)
  27. Richard F. Washell (1973), "Logic, Language, and Albert the Great", Journal of the History of Ideas 34 (3), pp. 445–450 [445].
  28. Goodman, Lenn Evan (1992); Avicenna, p. 188, Routledge, ISBN 0-415-01929-X.
  29. History of logic: Arabic logic, Encyclopædia Britannica.
  30. "Islam". Encyclopedia Britannica Online. (2007). Retrieved on 2007-11-27. 
  31. Steve A. Johnson (1984), "Ibn Sina's Fourth Ontological Argument for God's Existence", The Muslim World 74 (3-4), 161–171.
  32. Morewedge, P., "Ibn Sina (Avicenna) and Malcolm and the Ontological Argument", Monist 54: 234–49
  33. Mayer, Toby (2001), "Ibn Sina’s ‘Burhan Al-Siddiqin’", Journal of Islamic Studies (Oxford Centre for Islamic Studies, Oxford Journals, Oxford University Press) 12 (1): 18–39, Error: Bad DOI specified
  34. McGinnis, Jon (July 2003), "Scientific Methodologies in Medieval Islam", Journal of the History of Philosophy 41 (3): 307–327, Error: Bad DOI specified