Necessary versus probable cause

One finds in the systems of natural languages some explicit means of elaborating not only upon the directness of the causal relationship believed to exist between two events X and Y (i.e. some means of specifying just how inevitably event X gives or gave rise to event Y), but also some manner of indicating just who or what is understood to be the primary instigator of the caused event. The goal of the present paper is to explore these notions in detail and arrive at a formal, logic-based means of capturing them.