 Choice was, for a long time, a controversial axiom. On the one hand, it is of wide use in mathematics and, indeed, it’s key to many important theorems of analysis (this became gradually clear with works such as Sierpiński [1918]). On the other hand, it has rather unintuitive consequences, such as the Banach-Tarski Paradox, which says that the unit ball can be partitioned into finitely-many ‘pieces’ (subsets), which can then be rearranged to form two unit balls (see Tomkowicz &amp; Wagon [2019]). The objections to the axiom arise from the fact that it asserts the existence of sets that cannot be explicitly defined. During the 1920s and 1930s, there existed the ritual practice of mentioning it explicitly, whenever a theorem would depend on the axiom. This stopped only after Gödel’s proof of relative consistency, discussed below. 