Accounting: our first communications technology -- Merchants and mathematics -- Luca Pacioli: from Sansepolcro to celebrity -- Pacioli's landmark bookkeeping treatise of 1494 -- Venetian double entry goes viral -- Double entry morphs: the industrial revolution and the birth of a profession -- Double entry and capitalism; chicken and egg? -- John Maynard Keynes, double entry and the wealth of nations -- The rise and scandalous rise of a profession -- Gross domestic product and how accounting could make or break the planet