And that, perhaps, is the real infinity: not the equations, but the spaces between the page numbers.

More revealing are the ghosts between the lines. Try looking up . A few page references, perhaps to Ramanujan’s orthodox Brahmin upbringing. But racism ? You’ll find “prejudice” tucked under “English society,” as if the slur were ambient weather rather than a structural beam. Imperialism appears, but thinly. Food —a constant, heartbreaking drama in the book (Ramanujan cooking his own vegetarian meals in freezing Cambridge)—merits a handful of page numbers.

This is not a flaw. It is the index being honest about the book’s central tension: two men, unequal in the world’s eyes, made equal only by mathematics.

If you’re working from a digital “REPACK” (a cleaned-up, reflowed ebook or searchable PDF), the index becomes even stranger. You can now hyperlink. You can see which names cluster. Try this: follow —he appears a dozen times, always as “colleague of Hardy,” “reviewed Ramanujan’s work.” He is a satellite. Then follow Narayana Iyer, R. —Ramanujan’s mentor in India. Fewer entries, but each one freighted with “encouraged,” “recognized,” “believed in.”

So next time you pick up The Man Who Knew Infinity , skip the prologue. Turn to the index. Run your finger down the columns. What you’ll find is a second, smaller book—one of obsessive love, structural prejudice, and the silent geometry of who a biographer decides matters.

You don’t typically read a biography for its back matter. You read for the narrative sweep—the tragic prodigy, the Cambridge spires, the haunted eyes of Srinivasa Ramanujan. But when a book is as densely layered as Robert Kanigel’s The Man Who Knew Infinity (1991), the index becomes something more than an alphabetical chore. It becomes a hidden map of the book’s true soul.

Now search for . Go ahead. A reference to Ramanujan’s mother, Komalatammal. A mention of his wife, Janaki. And that’s almost it. The index doesn’t hide them; it simply has nothing more to list. In that silence, the index becomes a quiet indictment of the biography’s own blind spot.

The index, by giving it one line, mimics the biography’s own restraint. Kanigel knows we want the romantic tragedy—the dying mathematician shipping formulas home. The index refuses to overindex the miracle. It trusts you to find it.

The true genius of Kanigel’s index, however, is what it reveals about repetition . Scan the entries for , mock theta functions , modular forms . They appear, disappear, reappear. But then find notebooks (Ramanujan’s) . The subheads run: “contents of,” “Hardy and,” “lost notebook found.” That “lost notebook” sends you to a single page number. One. And yet the lost notebook (discovered in 1976 at Trinity College) is the book’s quiet emotional climax—the ghost that refuses to be buried.