Full Idea
The 'continuum hypothesis' says that aleph-one is the cardinality of the rational and irrational numbers.
Gist of Idea
The 'continuum hypothesis' says aleph-one is the cardinality of the reals
Source
Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.14)
Book Reference
Clegg,Brian: 'Infinity' [Robinson 2003], p.179