The 'impression' (species) can come only from the thing being present : but the expression (intentio rationis, logos, verbum mentale) of the thing endures in the understanding when the thing is away. So too does the corresponding phantasia, or sense-picture in the imagination, endure in the absence of the object. See Father Maher's Psychology, Stonyhurst Series, Longmans, ed. 4, pp. 51-53, 310.
Of God and His Creatures: 1.53