62As is well-known, this method is frequently used in mathematics to prove that a proposition q is true (q must be true if the assumption that q is wrong leads to a contradiction). Unfortunately, in mathematics it is much easier than in physics to decide whether or not a proposition is true. Likewise, it is much easier to decide if a contradiction should be considered as a ”paradox” (indicating a deep unsolved problem) or as a proper contradiction and plain nonsense (indicating an error in reasoning).