The guiding idea behind Grosseteste’s approach to a notion of non-temporal contingency is that even if a proposition such as “Antichrist will exist” (to use his standard example of a true, future contingent proposition) is true now and cannot become false until Antichrist comes into existence, the world might nevertheless have been such that “Antichrist will exist” was never true.  A present-day thinker might spell this idea out in terms of alternative possible worlds, but Grosseteste spells it out in terms of the notion of a proposition’s eternal power or capacity for truth or falsity without beginning, and grounds such powers ultimately in God’s eternal power to know or will propositions.