This paper suggests a Platonic source for Augustine's methodology in the later books of De Trin., where Augustine argues that we can begin to adumbrate the nature of God by examining the soul. Citing Genesis 1:26-7, Augustine finds validity in this procedure because the triune soul bears the likeness of the triune God. This is similar — indeed, formally identical — to Plato's method in Republic II, where Socrates seeks to examine the nature of justice in the soul by examining the nature of justice in the city, which he does because the (triune) city bears the likeness of the (triune) soul. The logic behind both analogies takes the form of an epistemic magnifying glass: If (A) is made in the image of (B), and (A) is easier to understand than (B), then one can begin to understand (B) by examining (A) in (B)'s stead. By plugging “the soul” (A) and “God” (B) into the equation, Augustine's method seems quite similar to Plato's.