The film *The Man Who Knew Infinity * goes on UK general release from 8th April.

It is a compressed, and beautifully dramatised version of the theme treated more fully in Robert Kanigel’s double biography of the same name – which treats Ramanujan alongside a partial portrait of G.H.Hardy.

Mathematicians can be remarkably unforgiving about attempts to present mathematics to a general audience. And Ramanujan’s story could so easily be cheapened – with awkward aspects being trivialised, in order to pander to current prejudices. The Good News is that, not only has this been avoided, but the film manages to incorporate much of the detail and spirit of what we know, while using its dramatic freedom to confront important issues that are often either treated too tritely, or passed over in silence. The project may have taken 10 years in the making, but the result has been worth it.

As someone who does not usually watch movies, I simply encourage everyone to see it

(perhaps several times), to encourage others to see it, and to use it to discuss the issues which it raises.

A film is not meant to be a reflection of reality. This film would seem to be a fairly faithful representation of what we know in those areas where fidelity matters. In other respects it exercises flexibility. In contrast to Ramanujan, Dev Patel is slim and beautifully formed; yet he manages to capture an essential seriousness and devotion which is entirely plausible. His wife is portrayed as older and I suspect much more beautiful than the real Janaki; yet her portrayal of profound simplicity is moving in a way that seems entirely appropriate (whether or not it is documented).

In his review for the February issue of the Notices of the AMS

George Andrews suggested that the film will help students appreciate the importance of “proofs”. In fact, the struggle between proof and intuition, between Hardy and Ramanujan, is not so cleanly resolved, and there is a danger that the film may leave many strengthened in their belief in mathematical invention as “magical intuition”. So the film should be used to actively encourage a deeper discussion of the relative importance of proof, and what is too often simply labelled “intuition” (as if it were not susceptible to, any further explanation).

Here is a chance to grapple with the often neglected interplay between

(a) technical, or formal, training in universal methods – whereby my individual “mental

universe” is disciplined to fit with yours (or with some imaginary “Platonic ideal”),

and

(b) our individual, idiosyncratic way of thinking about these shared objects and processes – whereby my thoughts avoid being mechanical replicas of everyone else’s, and so provide scope for originality.

Without the second, we are little better than machines. And without the first, we are almost bound to go astray.

Almost all students need a significant dose of (a) before their (b)-type thoughts can become fruitful. But some individuals’ (b)-type thoughts flourish – mostly unerringly – with relatively little (a)-type formalism. One thinks of Euler, or Schubert, or 19th century Italian algebraic geometers, or Feynman, or Thurston, or … . The problem is then how to check the resulting claimed insights, to embed them within mathematics as a whole, and to make the methods available to the rest of us. By neglecting such delicate matters we leave a vacuum that is too easily filled by half-truths.

Tony Gardiner