Putnam holds the view that mathematics, like physics and other empirical sciences, uses both strict logical proofs and "quasi-empirical" methods. For example, Fermat's last theorem states that for no integer formula_1 are there positive integer values of "x", "y", and "z" such that formula_2. Before Andrew Wiles proved this for all formula_1 in 1995, it had been proved for many values of "n". These proofs inspired further research in the area, and formed a quasi-empirical consensus for the theorem. Even though such knowledge is more conjectural than a strictly proved theorem, it was still used in developing other mathematical ideas.