“Where numbers only represent real things, you don’t need a number to express the absence of something. It is an abstract concept and only shows up when the math gets equally abstract. “The point about zero is that we do not need to use it in the operations of daily life,” wrote Alfred North Whitehead, the British mathematician, in 1911. “No one goes out to buy zero fish. It is in a way the most civilized of all the cardinal [numbers], and its use is only forced on us by the needs of cultivated modes of thought.”