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cf., Sent.I.D23.Q1.A1; QDePot.Q9.A1
Here, St. Thomas, after defining what "person" means in accordance with the descending method, uses both the development of Trinitarian grammar AND the differences between the Latin and Greek languages in order to confirm the definition via the ascending method.
He does this by comparing the term "person" with the terms "hypostasis," "subsistence," and "ousia/essence," "suppositum," and "res naturae."
Here, we see three stages.