“His failure, Feynman admitted, was to understand what the math was saying. It provided numbers: predictions of quantities that could be tested against experiments, and which invariably survived those tests. But Feynman couldn’t figure out what these numbers and equations were really about: what they said about the ‘real world’. One view is that they don’t say anything about the ‘real world’. They’re just fantastically useful machinery, a kind of black box that we can use, very reliably, to do science and engineering.”