The Salto Vitale Method in Philosophy

Did G. E. Moore prove the existence of things outside us? Philosophers have objected to his proof, but not for good reasons. Since when, for instance, has absolute certainty been the mark of philosophy? But Moore's proof was superfluous, as its conclusion had already been proved previously. (If immanent critique were the only acceptable way to refute a philosophy rationally, “Nothing exists” would be immune from refutation—which is preposterous.)