Definition:Intersection of Special Subsets

Definition
Let $g$ be a progressing mapping.

Let $x$ be a set.

Let $\powerset x$ denote the power set of $x$.

Let $A$ be the class of all $x$-special subsets of $\powerset x$ $g$.

We denote by $M_x$ the intersection of $A$:
 * $M_x = \ds \bigcap A$