Why we need paper promises
When you get into a taxi, there’s usually a framed sheet of paper describing what you pay for your trip: the cost of every mile travelled at different times of day, and the price of waiting time. As digital screens become ever cheaper, it won’t be long before someone suggests that there is no need to have these things any more. Instead a button will appear on the taxi’s new seatback touchscreen which will reveal the tariff when pressed. All very sensible, you may think. Except for this. The nature of a promise displayed on paper is subtly different to a promise displayed on a screen. Anything writ in liquid