# 1.11 Infinite Sets

## Russell's Paradox [and ZFC optional]

Exercise 1

In Russell's Paradox, $$W$$ is mathematically well-defined as a set. The question resides with "which well-defined collections are sets?" Russell's Paradox is not relevant when $$W$$ is not a set; even Russell himself knew that it was unjustified to assume that $$W$$ was a set! ZFC avoided Russell's Paradox by not allowing $$W$$ to be a set.
2. Zermelo-Frankel with Choice axioms (ZFC)

Exercise 2