Carl Jacobi was a nineteenth-century German mathematician who often used to say, “Invert, always invert” (actually he said, “Man muss immer umkehren,” because English wasn’t his first language). He meant that thinking about a problem from an inverse perspective can unlock new solutions and strategies. For example, most people approach investing their money from the perspective of making more money; the inverse approach would be investing money from the perspective of not losing money.