At: valuation wf 1 1 3
1. Q: Formula
Prop
2. 
F:{F:Formula| Q(F) }, a:Assignment. (F under a) 
3. x1: {F:Formula| Q(F) }
4. x2: Formula
5. Q(x2)
6. a: Assignment
(x1 under a) 
(x2 under a)
By:
MemberEqCD
THEN
HypBackchain
Generated subgoals:None
About:
