# Chance

### Bayes’s Theorem: the mathematical formula that ‘explains the world’

Here’s a profound question about beards: is the number of acrobats with beards the same as the number of bearded people who are acrobats? Go with your gut instinct. It’s not a trick question. If you answer ‘yes’, then you’ve understood the central idea behind Bayes’s theorem. If you’re one of those people who likes to titter about how bad you are at mathematics, stop it. Retake your GCSE, learn how to pin this obviousness down in symbols, and you can produce artificial intelligence, forecast stock market collapses and understand this: P(A|B) = (P(B|A)∙P(A))/(P(B)) This is Bayes’s equation, the formula which, as Tom Chivers insists in this remarkable, bold book,

### A deadly game of chance: The Story of a Forest, by Linda Grant, reviewed

‘Like a child in a fairy tale’, 14-year old Mina Mendel walks into a Latvian forest one day in 1913. With her basket and shawl, she looks like Little Red Riding Hood, but the wolves she meets – Bolsheviks, ‘agents of the coming revolution’ – are anything but mythical. Linda Grant begins her sweeping, ambitious ninth novel The Story of the Forest with this accidental encounter. From Latvia to Liverpool – and Soho to World’s End – she tells the story of one Jewish family in the 20th century as they live through plots to overthrow the tsar, the trenches of of the Great War, the racism of Liverpudlian suburbs