Mutualism or correlativism are virtual synonyms. Cornelius Van Til, a prominent twentieth-century Reformed theologian, apologist, Orthodox Presbyterian, and founding member of Westminster Theological Seminary, taught that God and the creature at no point share in a common mode of development or becoming. He said that there is no point of correlativity—of mutual sharing and being or knowledge between the Creator and the creature. Even in the relation God remains unchanged and self-contained, and the creature remains the creature, dependent and derived. There is no correlativism or “mutualism,” is a more contemporary synonym.
To affirm mutualism is to say that in the Creator-creature relation, God and man are submerged in a common process of mutual development through time. “Correlativism” is Van Til’s older way of putting it while “mutualism” is a newer way of putting it. You could even add a third category of “personalism” in which some unorthodox theologians locate change in the Trinitarian persons. In other words, the persons would have un-actualized potential and change in their relation to creation.
Those views—whether relativism, mutualism, personalism, or any other view similar—erode and deny the integrity of the Creator-creature distinction by making God and man participants in a common thing. It’s a third thing that is neither fully God or fully man but something contingent like time, change, process, or history. Orthodox, biblical, creedal, and confessional theology is anti-correlativist, anti-mutualist, and anti-personalist, because it maintains the immutability of God in his freely determined relation to the mutable creature.