For Christian theology, the eschaton represents both a mystery and a problematic. On the one hand, it expresses a mystery preached and promised by Jesus Christ as the culmination of his work, which penetrates history by confronting the Church, the individual, and history itself with a parousia from beyond. It is a constant experience (and expectation) of the ongoing revelation and action of the Trinitarian God, who, by the Spirit, makes present in time—primarily in the Eucharist—his promised kingdom. The Church is called upon to cooperate to establish this kingdom already in the now of the world.