The class of phases, during which no changes happen.
(=> (*State ?Self) (Exists (?Y ?Z) (And (Situation ?Y) (Situation ?Z) (Context-Of ?Y ?Self) (Exists (?A) (And (Beginpoint ?Self ?A) (Co-Occur ?Y ?A))) (Context-Of ?Z ?Self) (Exists (?B) (And (Endpoint ?Self ?B) (Co-Occur ?Z ?B))) (Equal-But-Time ?Y ?Z))))