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cf., Sent.I.D36.Q1.A1; Sent.II.D3.Q3.A3; SCG1.C50, 63, 65; QDeAn.Q20; QDeVer.Q2.A5; CT.BookI.C132-133; Peri.Bk1.L14
He provides a scientific proof by showing, in the beginning of the article, that our knowledge of singular things is a perfection. Thus, we ought to attribute it to God in an eminent manner.
He then answers the further question of "how?"
The first solution he gives is that God knows singulars because singulars are contained in universals. But, this is not a satisfying solution. For, singulars are individuated by their signate matter which, by definition, goes up and beyond what is universal.