  To understand Skolem's Paradox, we need to start by recalling two theorems from classical  logic.[1]  The first comes from the late 19th century. In 1873, Georg Cantor formulated a new technique for measuring the size—or cardinality—of a set of objects. Cantor's idea was that two sets should have the same cardinality just in case their members can be put into one-to-one correspondence with each other. So, for instance, the set {1, 2, … , 26} can be put into one-to-one correspondence with the set {A, B, … , Z } via the natural map which relates 1 to A, 2 to B, 3 to C, etc., etc.; similarly, the set of natural numbers can be put into one-to-one correspondence with the set of even numbers via the map: x   2x.