Complex sentence: The existence of Sierpinski sets is independent of the axioms of ZFC: they exist if the continuum hypothesis is true, and do not exist if Martin's axiom for ℵ 1 is true.
Split into simpler sentences: The existence of Sierpinski sets is independent of the axioms of ZFC. On the other hand, they do not exist if Martin's axiom for ℵ 1 is true.