Lemma
(Cohen Lemma)
.
Assuming that:
T
⊆
ZFC
Then
there is finite
T
∗
⊆
ZFC
such that if
M
is a
countable transitive model
of
T
∗
, then there is
N
⊇
M
such that
N
is a
countable transitive model
of
T
+
¬
CH
.