Thomas Aquinas, Compendium of Theology

To know contingent futures in this way, as being actually in existence, that is, to have certitude about them, is evidently restricted to God alone, of whom eternity is truly and properly predicated. For this reason, certain prediction of future events is accounted a proof of divinity. This accords with Isaias 41: 2 3: "Show the things that are to come hereafter, and we shall know that ye are gods." Knowledge of future events in their causes is, indeed, possible for others. Such knowledge, however, is not certain, but is rather conjectural, except as regards effects that necessarily flow from their causes. In this way a physician foretells future illnesses, and a sailor predicts storms.