Carl Jacobi

German mathematician who made foundational contributions to elliptic functions and determinant theory — and whose advice to 'invert, always invert' became a mental model cornerstone through Charlie Munger.

Invert, always invert: Jacobi's mathematical strategy — to solve a difficult problem, try to work backwards from the answer, or reformulate it as its inverse — became one of Charlie Munger's most cited mental models. 'All I want to know is where I'm going to die so I'll never go there.' The inversion mental model: to achieve X, find what prevents X and eliminate it. Jacobi's actual mathematical contributions (Jacobi elliptic functions, the Jacobian determinant, fundamentals of matrix algebra) are independently significant but reached entrepreneurship culture through Munger's appropriation.