(Felsefe) A vanishing mediator is a concept that exists to mediate between two opposing ideas, as a transition occurs between them. At the point where one idea has been replaced by the other, and the concept is no longer required, the mediator vanishes. In terms of Hegelian dialectics, the conflict between thesis and antithesis is resolved by a synthesis of the two ideas, although the synthesis represents the final solution, whereupon the mediator vanishes