According to this objection, then, some propositions change their truth values over time, and a being who knows all true propositions accordingly changes beliefs. So, if God is omniscient, he is not immutable (Kretzmann’s formulation) or eternal (Wolterstorff 1975) or timeless (Davis 1983). Variations on this objection have also been given by Kenny (1979), Prior (1962), and Grim (1985). Philosophers who have objected to the argument include Castañeda (1967), Kretzmann himself subsequently in Stump and Kretzmann (1981), Kvanvig (1986), Pike (1970), Swinburne (1993, but not 2016), and Wierenga (1989, 2002).