Axiom of choice

The axiom of choice is a mathematical postulate about sets: for each family of non-empty sets, there exists a function selecting one member from each set in the family. If those sets have no member in common, it postulates that there is a set having exactly one element in common with each set in the family. First formulated in 1904, the axiom of choice was highly controversial among mathematicians and philosophers, because it epitomized ‘non-constructive’ mathematics. Nevertheless, as time passed, it had an increasingly broad range of consequences in many branches of mathematics.