The Man Who Knew Infinity is a 1991 biography of famed Indian mathematician Srinivāsa Ramanujan, written by Robert Kanigel. The text closely follows Ramanujan’s rise from humble origins to become one of the most influential mathematicians of the 20th century. Joining forces with another notable mathematician in his own right, G. H. Hardy of Cambridge University, Ramanujan produced some of the most insightful, imaginative, and original work in mathematics that is still studied today.

From Ramanujan’s early childhood, when he nearly died of smallpox, to when he dropped out of college, Kanigel chronicles the many obstacles that Ramanujan overcame to become the legendary figure that he was. Ramanujan’s path to iconic status depended in no small amount on the friendship of G. H. Hardy, and for this reason, Kanigel devotes some time to Hardy’s biography as well. While this is a book primarily about Ramanujan, it is also a book about his collaboration with Hardy. Though from entirely different walks of life, Ramanujan and Hardy found commonality in math, and their work together serves as an example for what humanity can achieve when the spirit of collaboration prevails.

The book inspired a 2016 film of the same name, directed by Matt Brown. The edition used for this guide is the 2013 Kindle edition.

Summary

The book begins by offering a portrait of Ramanujan’s early childhood. He was born into humble circumstances; his family was poor. When he was two years old, Ramanujan was stricken with smallpox and was lucky to survive. By the time he was six, Ramanujan had lost three siblings to disease.

From a very early age, Ramanujan was bright and intelligent. In grade school, he would often propose questions that seemed advanced beyond his years. He would offer philosophical conundrums to teachers and was always quick to challenge generally regarded truths. Ramanujan was also raised in a religious culture and was primarily influenced in this regard by his mother. A traditionalist by nature, Komalatammal raised her son to be mindful and always aware of his Brahmin caste status. As someone predisposed to mystical explanations for phenomena that defied rational explanation, Komalatammal influenced her son to be the same way. As a result, Ramanujan maintained that his gifts were of divine origin and that his great insights were revelations sometimes discerned from dreams. He was a man incredibly gifted in the use of human reason who also held beliefs that would defy it.

As Ramanujan grew into adulthood, he was met with his first tastes of failure. He had been accepted into Government College in Kumbakonam, but because he was so obsessed with math, he neglected other required courses. Ultimately, his scholarship was rescinded and he was forced to drop out. A similar circumstance would happen a short time later at Pachaiyappa College. Ramanujan’s response was dramatic, and he disappeared. Though he sometimes came across to others as aloof or even strange, his reaction to failure signals a different aspect of his personality. He sought affirmation for his genius and looked to validate it among his peers. When something happened that contradicted this need, he was humiliated. He was sensitive about his reputation.

As Ramanujan continued to seek validation, it soon became clear that people in India did not know what to make of his work. Well-esteemed individuals were weary of supporting him and going out on a limb on his behalf. This was mainly because his work was so advanced that even the best mathematicians in India at the time could not fully understand it. In response, Ramanujan set his sights elsewhere and reached out to England’s Trinity College, Cambridge.

After unsuccessfully petitioning two other mathematicians at Cambridge, Ramanujan finally found the validation he sought from G. H. Hardy, notable Cambridge mathematician and intellectual. In 1914, Ramanujan moved to England and began his tenure at Cambridge alongside Hardy. The collaboration was an astonishing success, and the two men would work together on theorems and formulas that would have a significant and lasting impact on mathematics through the 20th century and into 21st century.

As Ramanujan experienced success in England, he struggled to adapt to the different culture and climate. Though he cherished his work with Hardy, he was often lonely and isolated from Cambridge society. World War I was in full swing, and the disastrous effects of the war loomed large in every corner of English society, including Cambridge. Eventually, Ramanujan would be stricken by tuberculosis.

As his health steadily deteriorated, Ramanujan continued his work. Eventually, he was awarded the distinguished honor of membership in the Royal Society. As the war ended and passenger shipping restarted, the time came for Ramanujan to return home. When he finally arrived in India in 1919, Ramanujan’s health had declined drastically. He would spend the last year of his life suffering through the devastation wrought by tuberculosis. In 1920, he finally succumbed to the disease.

Kanigel continues to examine Ramanujan’s life and the legend that grew up around him. As the century moved into its second half, Ramanujan was revered to the same degree as notable Indian figures such as Gandhi and Nehru. His legacy is still relevant, and his work is studied by mathematicians, physicists, chemists, statisticians, and others.