In the ancient Greek civilization, it was believed that sight was possible because eyes emitted light rays. Ibn al-Haytham , the 10th century muslim scientist, was the first to correctly state that vision results from the rays of light entering eyes from the each point on an object.

Ibn al-Haytham's full name was Abu Ali al-Hasan ibn al-Hasan ibn al-Haytham (965 - 1039) and he is commonly known in the west by his latinized names: Alhazen, Alhacen, or Alhazenihas. He is regarded as the 'Father of Modern optics' and the 'Founder of Experimental physics' due to his enormous contributions in these areas. He is also given the credit of being the pioneer of modern scientific method as he was the first to introduce the modern scientific procedures of analyzing a problem (more on this in a future post). One of Al-Haytham's famous work was 'Kitab Al-Manazir' (The Book of Optics), a seven volume treatise related to optics and vision, in which for each of his hypothesis he either performed a physical test or presented mathematical proofs.

Before Al-Haytham, there were basically two theories of vision: according to the first theory, put forward initially by Euclid and and later supported by Ptolemy, eyes emitted rays of light. The second theory was that of Aristoltle who believed that an object being looked at alters the medium between itself and the eye by sending some sort of force to the eye. Al-Haythem rejcted both these theories and stated that vision was possible because of rays of light traveling from visible objects to the eye. This is now known as modern intromission theory of vision.

Al-Haytham also gave the anatomy of eye and was the first scientist to state that brain and not the eye was responsible for the perception of image.

According to the Historian Ian P Howard in 'Alhazen's neglected discoveries of visual phenomena' on 'Books of Optics':

"Book I [of seven volume Book of Optics] deals with optics, the structure of the eye, image formation in the eye, and with the visual pathways. This book inspired all other books on optics from the thirteenth to the seventeenth century and formed the basis upon which Kepler solved the problem of image formation. However, Alhazen's work contained in Books II and III has been almost totally ignored. These two books contain an account of hundreds of observations and experiments carried out by Alhazen on a broad range of topics which are now studied under the heading of visual perception. He clearly enunciated many of the fundamental principles which are credited to scientists living in the past two hundred years, including a theory of unconcious inference; the law of equal innervation of the eye muscles; the principles of binocular direction; constancy of size, shape, and colour; induced visual motion; the vertical horopter; the fusional range of binocular disparity; and many others."

Ibn Sina (980 - 1037CE) and Al-Biruni (973 - 1048 CE), two of the greatest scientists during the medieval Islamic civilization, had an intellectual correspondence that was started by Al-Biruni asking Ibn Sina a few questions related to Philosophy, Astronomy and Physics. This interesting debate was translated in english by Rafik Berjak and Muzaffar Iqbal and published as a series of articles in 'Islam & Science', with Thomson Gale as publisher.

Al-Biruni began this debate by qutestioning certain Aristotle's theories. Ibn Sina replied in a scholarly manner but Al-Biruni was not satisfied with his answers. Al-Biruni replied back criticzing each answer that he had received by giving his own logical arguments and at the same time asking him further questions. This exchange of letters resulted in a written debate in which Al-Biruni asked Ibn Sina a total of 18 questions. In the later stages, Ibn Sina asked one of his prominent student, Ahmad ibn Ali al-Masumi to reply on his behalf.

As an example, following is an initial exchange of questions/answers between these two great polymaths related to Vision.

Al-Biruni:

How is vision possible? Why can we see beneath water whereas the ray of vision reflects off opaque bodies and the surface of water is opaque?

Ibn Sina:

According to Aristotle, vision is not the result of the rays coming out of the eye; that is Plato's view. Although, upon examination, one finds that there is no [real] difference between the sayings of the two, for Plato said this for the commoners in their slang. This has been explained by Shaikh Abu Nasr al-Farabi this in his book al-Jam bayna Ra'yain al-Hakimin (The Concordance Between the Opinions of the Two Wise Ones). In Aristotle's opinion, vision results from the contact of the vitreous humor(al-ratubatul jalidiyyah) of the eye with the transparent surface; [upon contact, vitreous humor] picks up the colors that are facing it at the parallel point of the body of which the color is the property. Since the vitreous humor is transparent, it would change and react to this color. And when this gelatinous substance changes, it becomes the instrument through which the faculty of vision perceives, this faculty recognizes the reaction that occurs and that is how vision becomes possible. There are more details about it in the commentaries on Book II of Kitab al-Nafs (On the Soul) by the Philosopher and [in the commentaries] on his Kitab al-Hiss (Sense and Sensibilia). So if that was that, and [since] water and air are transparent bodies presenting the nature of colors to the senses, doubt should disappear.

Al-Biruni:

Your answer presented Aristotle's definition of the vision but not the explanation, and sometimes the definition of a thing requires many different interpretations. According to what you said, the one who sees would not be able to distinguish between dimensions, and [as such] he will perceive small [objects] nearby to be identical to large distant [objects]; and so too would be the case with sounds: loud sounds further away would be heard just as would quiet sounds closer by, the listener being unable to distinguish between the different sounds from their sources. If the transparent [body] were affected by color, then a glass stained with black on one side when looked upon through any other side--except from the side opposite to the blackened side--should look black. The question was not about perception of what is under the surface of water, but I had asked [rather] about the understanding of how vision penetrates based upon the understanding of reflection of the rays simultaneously under the surface of water.

Ibn Sina and and later his student had replied again, and in much more detail, to the criticism above. The purpose of quoting here this initial correspondence, related to vision, was simply to get a glimpse of the analytical approaches of the two great minds.

Ibn Sina was a tenth century Muslim scientist who had made major contributions in many diverse areas - from Medicine, Psychology and Pharmacology to Geology, Astronomy,Physics, Chemistry and Philosophy ... a true polymath! The lunar crater ‘Avicenna’ and the mountain peak ‘Ibn Sina Peak’ are named in his honor.

This is the first post in the series where highlights of major contributions of individual scientists are provided. I'm thankful to  Tricia  who had shown interest and suggested that details should also be provided.

The following contributions are only the ones that Historians have been  able to find from Ibn Sina's  240 surviving books out of a total of 450 books written by him. To find more about the causes of destruction of many great works please read the post 'Pubic Libraries in the Medieval Islamic World ' .





Full Name:  Abu Ali al-Ḥusayn ibn Abd Allah ibn Sina

Latin Name: Avicenna

Period:  980 - 1037CE

Areas of Contributions:  Medicine, Pharmacology, Philosophy, Chemistry, Astronomy, Music, Physics, Geology, Psychology, Poetry and Engineering

Total Number of Books:  450

Most Famous Books:

1. 'Al-Qanun fi’l-tibb' - The Canon of Medicine (14 volume medical encyclopedia with over one million words!)
   
2. 'Kitab al-Shifa' - The Book of Cure  or The Book of Completion (scientific and philosophical encyclopedia)
3. 'Fi aqsam al-ulum al-'aqliyyah' -Classification of the Rational Sciences
   

Regarded as:    Father of Modern Medicine. Father of Clinical Pharmacology and Father of Geology due to his founding contributions in these areas.

MEDICINE:

1. Separation of medicine from pharmacology
   
2. Discovery of sexually transmitted diseases
   
3. First detailed description of skin problems, perversions and nervous ailments
   
4. Introduction of systematic experimentation and quantification into the study of physiology
5. First description of Meningitis
6. First known treatment of cancer. Discovery of cancer as a tumor. Related Post 
7. Discovery of the causes of bleeding and hemorrhage
8. First descriptions of bacteria and viral organisms
   
9. Description of working of heart as a valve
   
10. First diagrams of the cranial sutures
    
11. Discovered that madness is a disorder of reason with its origin in the middle part of the brain (unlike Medieval physicians in Europe who believed that Demonic Possession  was the explanation for the mental illnesses and as such as late as till 18th century mentally ill patients were subjected to many tortuous inhuman treatments that included whipping,bloodletting and starvation. Related post )
12. Introduction of quarantine for contagious diseases
13. Identification of tuberculosis and phthisis as contagious
    
14. First description of the surgical procedure of intubation
    
15. Distinguished anatomy from medicine
    
16. Discovered the cerebellar vermis and the caudate nucleus (Neuroanatomy)
    
17. Gave correct descriptions, for the first time, on the physiology of eye movements, conjuctive sclera, cornea, choroid, optic nerves, iris, and central and peripheral facial paralyses - still used in modern Opthomology
    
18. Discovery of the healing property of gaseous mercury
    
19. First correct explanation of pulsation 
20. Put forward new methods for hepatitis treatment
    
21. Provided a number of new methods for Inhalation and Oral anesthesia. Related Post
    
22. First explained the distribution of diseases by water and soil
    
23. Diagnosis of  diseases using only the methods of feeling the pulse and observing inhalation
    
24. Described diabetes insipidus very precisely for the first time
    
25. Provided the distinction of mediastinitis from pleurisyo .
    

PHARMACOLOGY:

1. Laid down the principles for testing the effectiveness of new drugs and medications that form the basis of clinical pharmacology, clinical trials, randomized controlled trials and efficacy tests.
   
2. The Canon lists 760 tested drugs describing their pharmaceutical actions and properties. Many were his own contributions while for the rest he gave credit where due.
   

PSYCHOLOGY:

1. Pioneer of neuropsychiatry. First described the neuropsychiatric conditions of hallucination, insomnia, mania, rabies, nightmare, melancholia, dementia, epilepsy, paralysis, stroke, vertigo and tremor and provided treatment methods
   
2. Described melancholia (depression) as a type of mood disorder in which the person may become suspicious and develop certain types of phobias
   
3. Developed a system for associating changes in the pulse rate with inner feelings
   

GEOLOGY

:

1. First to emphasize the role of sedimentary and erosive phenomena in the formation of mountains
   
2. First to present the fundamental principles of Geology that later became known in Europe as ‘Doctrine of Uniformitarianism’,’ law of superposition of strata’ and ‘Concept of Catastrophism’

ASTRONOMY:

1. Criticized Aristotle's view of the stars receiving their light from the Sun. Ibn Sina stated that the stars are self-luminous
   
2. Concluded that Venus is closer to the Earth than the Sun
   
3. Solved the equant problem in the Ptolemaic model
   

PHYSICS:

1. Developed a detailed theory of motion. The concept of inertia put forward in this theory was consistent to that given by Isaac Newton about seven centuries later in his famous first law of motion
   
2. Considered pioneer in putting forward the concept of momentum that is part of  Newton’s second law of motion.
   
3. Invented air thermometer to measure the relative hotness and coldness of dry air
   
4. Stated 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
   

CHEMISTRY:

1. Invention of steam distillation
   
2. Invention of refrigerated coil
   
3. One of the first to refute alchemy. Four of his works on this subject were translated into Latin
   

PHILOSOPHY:

1. Wrote more than 150 treatises on Philosophy
   
2. Founder of ‘Avicennism’ – a school of thought of Islamic Philosophy that had an influence on later European Philosophers including William of Auvergne, Albertus Magnus and Thomas Aquinas. In Paris, however, Avicennism was proscribed in the early thirteenth century.
   
3. Developed an early theory on ‘hypothetical syllogism’
   
4. Developed an original theory on temporal modal syllogism
   
5. Developed an early theory on ‘propositional calculus’
   
6. First to describe the methods of ‘agreement, difference and concomitant variation’ that are part of Mill’s methods.
   
7. Wrote the first criticisms of ‘Aristotelian logic’
   
8. Wrote a number of treatises on Islamic theology in which he gave scientific and philosophical interpretations of Quran

MUSIC:

1. Belived that music had both  physical as well as psychological effect on patients
   
2. Followed Al-Kindi in classification of Music as a branch of Mathematics. Translated title of his book on Music is, therefore, ‘Chapter three of the mathematical sciences which is on the science of music’.
   
3. Observed that in the series of consonances represented by (n + 1)/n, the ear is unable to distinguish them when n = 45
   

ENGINEERING:

1. First to classify five constituent simple machines - lever, pulley, screw, wedge, and windlass - and their combinations
   
2. First correct description of 'Mechanism'

POETRY:

Various verses written by him are present in many of his works. These are written in Arabic as well as in persian.

OTHERS: 

Ibn Sina had memorized the Qur'an by the age of seven.

The historian George Sarton, who is regarded as 'Father of History of Science', wrote in his famous work 'Introduction to the History of Science:

"One of the most famous exponents of Muslim universalism and an eminent figure in Islamic learning was Ibn Sina, known in the West as Avicenna (981-1037). For a thousand years he has retained his original renown as one of the greatest thinkers and medical scholars in history."

The Book of Animals ('Kitab al-Hayawan'), written by Al-Jahiz in the 9th century, is one of his most famous works. It is a seven volume book, described by many as an encyclopedia, that mentions over 350 varieties of animals. This book is most famous for describing the theory of evolution about 1000 years before Charles Darwin.

The 'Book of Animals' is quite unique as it has both lierarary as well as scientific value. The book contains anthology of animal anecdotes, proverbs and poetry and is considered a fine example of arabic prose. At the same time, the 'Book of animals' is famous for the following scientific contributions:

1. First known scientific attempt of classification of animals.
   
2. First description of the concept of food chain giving detailed examples.
   
3. Discussion of the social behavior, psychology and degree of intelligence in animals.
   
4. First description of the theory of biological evolution that beame foundation for many later theories. He based his theory of evolution on three mechanisms: Struggle for Existence, Transformation of Species into each other and Environmental Factors.

In 'The Book of Animals', Al-Jahiz wrote:

"Animals engage in a struggle for existence [and] for resources, to avoid being eaten and to breed.... Environmental factors influence organisms to develop newcharacteristics to ensure survival, thus transforming into new species. Animals that survive to breed can pass on their successful characteristics to [their] offspring."

Consequently, this book had a great influence on later scientists including Darwin.According to Historian Dr.Mehmet Bayrakdar:

"Indeed, Darwan and his precursors took up the theory of al-Jahiz as the base for the essentiality of their evolutionary theories and they formulated it in a more scientific way in the context of eighteenth and nineteenth centuries development of science."

Now, the unauthentic part: I came accross a post in a discussion forum where the member had written that his history teacher herself had gone to the British National Library and discovered that there was only one copy of al-Jahiz's work in their collection and that too was missing. After checking the records, she discovered that the last person to whom the book was issued was Charles Darwin - who never returned it! If any of the readers have access to the British National Library and could please verify it, this would be of great help in finding the truth. Thanks.