# Table of Contents
- [`[2017-11-30]` Continuum hypothesis](#cntnmhypthss)
- [`[2015-08-26]` depenedent sum](#dpndntsm)
- [Self-reference elimination: use indices](#slfrfrnclmntnsndcs)
# `[2017-11-30]` Continuum hypothesis
Godel: proved that ZFC + CH is consistnent
Cohen: proved that ZFC + ~CH is consistnent (actually, any intermediate number of infinities)
# `[2015-08-26]` depenedent sum
Sum (a : A) (B(A)) = {(a, b) | a ∈ A, b ∈ B(a)}
Exists (a : A) (B(A)) = || Sum a B ||
# Self-reference elimination: use indices
x1 ∈ y2
y2 ∈ x1: forbidden!
x1 ∈ x2: forbidden!
System NF?