What is The Man Who Knew Infinity about?

Srinivasa Ramanujan was born in 1887 in the South Indian town of Erode into a Brahmin family of modest means, received almost no formal mathematical training, and by his mid-twenties had filled notebooks with thousands of mathematical formulas, many of them original results that professional mathematicians would spend decades verifying. Robert Kanigel's biography reconstructs how this happened, and what happened next — Ramanujan's extraordinary correspondence with Cambridge mathematician G.H. Hardy, his five years in England from 1914 to 1919, and his death at 32.

The biography works as two interwoven stories. One is Ramanujan's: his early mathematical obsessions, the poverty that repeatedly interrupted his education, his deep religious conviction (he attributed many results to his family goddess Namagiri), and the social and physical dislocation he experienced in cold, wartime Cambridge. The other is the context: what British India looked like in the early 20th century, how Cambridge mathematics worked, how Hardy — himself a celebrated mathematician and an atheist who regarded Ramanujan's religious explanations with polite bafflement — navigated the mentorship of someone whose working methods he couldn't fully understand.

Kanigel explains enough mathematics to make Ramanujan's achievements legible without turning the book into a textbook. The central mystery of Ramanujan — how he produced so many correct results, often without proof, often using methods that weren't standard — remains genuinely open. Hardy believed Ramanujan's intuition was unequaled; that he somehow saw results directly in a way that bypassed formal argument. Hardy famously rated Ramanujan a 100 on a scale where Hardy himself scored 25 and the best contemporaries scored 35.

The book is long — over 400 pages — and the first chapters, covering Ramanujan's childhood and South Indian culture in detail, move slowly. Readers willing to stay with it are rewarded. The friendship between Hardy and Ramanujan, two men with almost nothing in common beyond an obsession with the same subject, becomes one of the more moving intellectual partnerships in scientific biography. And Ramanujan's illness and death — he died of tuberculosis in 1920, a year after returning to India — gives the whole narrative an elegiac weight.