Economic model

Oh dear. In the book review "Out of nowhere into the limelight" (12 November), Natalie Gold claims that: "In Economics Is a Serious Subject (1932), (Joan Robinson) argued that economists should use tractable assumptions, at the expense of treating simplified problems rather than tackling the real world."

It is not clear what this means, but economists (including Robinson), for good or ill, use mathematically tractable simplifications as a way of tackling reality. Perhaps an economics reviewer would have been more appropriate?

Michael Williams, Economist and philosopher (retired).