In this case study, we illustrate the great potential of experimental mathematics and symbolic computation, by rederiving, ab initio, Onsager's celebrated solution of the twodimensional Ising model in zero magnetic field. Onsager's derivation is extremely complicated and ad hoc, as are all the subsequent proofs. Unlike Onsager's, our derivation is not rigorous, yet it is absolutely certain (even if Onsager did not do it before), and should have been acceptable to physicists who do not share mathematicians' fanatical (and often misplaced) insistence on rigor.