He was born Muhammad ibn Muhammad ibn Hasan in Toos in the year 597 AH. His father was himself a noted scholar, and he received much of his early education from him. Being from Toos and for his great services to the faith, he became better known as Naseeruddin (Helper of the Religion) Tusi.
(For the sake of brevity, he will be henceforth referred to as "Shaikh Tusi". He is not to be confused with Shaikh Abu Ja'far Tusi, who established the seminary in Najaf and preceded him by about 200 years.)
During his early lifetime, Shaikh Tusi witnessed some bitter Shia-Sunni conflicts. In order to unite Muslims, he set about writing a book that contained narrations regarding the importance of the Ahlul Bayt (peace be upon them). These narrations were ones that all schools of thought in Islam agreed upon. After almost 20 years of hard labor, he finished the masterpiece and went to present it to the caliph.
The caliph at the moment was vacationing near the Tigris river along with his vizier. He took the book from Shaikh Tusi and handed it to the vizier. Being an enemy of the Ahlul Bayt, the vizier tossed the book into the river and mocked Shaikh Tusi. The aggrieved scholar returned home and prayed for justice. That night, he dreamed that he was standing in front of a wall upon which a very long supplication was inscribed. A man happened to be standing near the wall. The Shaikh inquired as to who he was. The man told him that he was the 12th Imam (may Allah hasten his reappearance).
The Imam told Shaikh Tusi to memorize the supplication and that it would help him overcome his adversary. The supplication survives to this day as the second Du'a Tawassul listed in many prayer manuals, including Mafatihul Jinan.
Shortly thereafter, Shaikh Tusi joined the palace of an Ismaili prince in order to be able to better spread the message of Truth. The Mongols were on the rise in central Asia, and eventually this small kingdom was conquered by Halaku Khan. Seeing Shaikh Tusi's brilliance and widom, Halaku appointed him as prime minister. He often attempted to convert Halaku to Islam, but given the latter's primitive origins and little interest in anything beyond warfare and conflict, he was not too successful. In 656 AH, Halaku invaded and ransacked Baghdad, bringing an end to the Abbasid caliphate. Shaikh Tusi saw the Imam's prophecy come true, as he was able to arrest and punish the vizier for committing atrocities against himself as well as thousands of other Shias.
Many people have condemned Shaikh Tusi, blaming his complicity with Halaku as a result of his alleged animosity towards the Sunni political establishment. The truth of the matter is that Shaikh Tusi had little choice in the matter. If he had refused to serve Halaku, he most certainly faced death. By working with Halaku, he was able to spread Shi'ism to several distant parts of the world, and it is said that he did more to propagate the Truth than probably any other person in history. Furthermore, it should be noted that the Muslims themselves did nothing during this period to prevent their impending defeat. As Mongol armies swept through Khorasan, passionate debates were taking place in Baghdad regarding the permissibility of eating owl meat!
Following the conquest of Baghdad, Shaikh Tusi convinced Halaku to build an observatory in the northern regions of Iran. The study of astronomy was thus formally established in the Islamic world for the first time. Long before Copernicus and Galileo, Shaikh Tusi argued that the Earth rotated on its axis and proposed the heliocentric model of the universe. His "Tusi-couple" for linear motion replaced the "equant" developed earlier by Ptolemy and is still used today in the field of applied mathematics. His work with binomial expansion later led to the development of Pascal's Triangle. Over 500 years before Antoine Lavoisier, he proposed the law of conservation of mass, and 600 years before Charles Darwin, Shaikh Tusi discussed the possibility of "evolution by natural selection". Today, geometry students are indebted to him for creating the famous equation "a/sin(A) = b/sin(B) = c/sin(C)".
Yet Allah has a way of reminding even his greatest servants of their lowliness before Him. Once while he was travelling, Shaikh Tusi camped outside a miller's house for the night. The miller told him that it would rain that night, but the Shaikh assured him that his calculations indicated to the contrary. In the middle of the night, it began to pour. The Shaikh ran inside, and later he admitted to the miller that he must have made a mistake in his calculations. However, he wanted to know how the miller came to know that it was going to rain. The miller replied, "I have no knowledge of such things. However, my faithful dog here does. If it's supposed to rain on a night, he comes inside to sleep, but if it won't rain, he stays outside. He came inside today, so I figured it must rain." The Shaikh smiled and said to himself, "O Tusi, you thought you were so knowledgeable and learned, yet even the miller's dog can predict the weather better than you!"
Visiting Baghdad one day, Shaikh Tusi fell ill and passed away in the year 672 AH. He was interred in the shrine of the 7th and 9th Imams (peace be upon them) in Kadhmiyya, and as per his wishes and as token of his humbleness, an inscription with Verse 18 of Sura Kahaf (referring to the dog of the People of the Cave) was hung on his grave: "…while their dog lay outstretching its paws at the entrance."
In honor of his contributions to the sciences, a lunar crater ("Nasireddin"), a minor planet ("10269 Tusi"), and the K. N. Toosi University of Technology in Iran are named after him.
EDITOR'S NOTE: These articles are adaptations of lectures delivered by Maulana Sadiq Hasan in Karachi, Pakistan, during the 1980s on the lives of the great scholars of Islam. The Urdu lectures can be accessed at Hussainiat.com. For previous articles in this series, please look under the History section.