Some definitions of interest.
stable	Def Stable{P} == P  P
	Thm* A:Prop. Stable{A}  Prop
not	Def A == A  False
	Thm* A:Prop. (A)  Prop
sq_stable	Def SqStable(P) == P  P
	Thm* A:Prop. SqStable(A)  Prop
squash	Def T == {:True| T }
	Thm* A:Prop. A  Prop

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