The theory that all consequences upon the path of existence were decided at a root point cannot be disproven upon its assumption. Murphy's law’s definiteness is rooted in the fact that we do not know the future. Though we feel we can change the future, we truly cannot. by choosing to do any action however consequential, you do not change the path of reality that was destined at its root. You simply knock it off course, keeping its validity as the one true reality.