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Although St. Thomas Aquinas is said to have "reconciled" Aristotle with Christian theology, he rejects much of Aristotle (e.g., he rejects that Aristotle thought the world is eternal).
(Interestingly, St. Thomas refers to Aristotle as "Aristotle" when he disagrees with him and as "The Philosopher" when he agrees with him.)
St. Thomas can be understood without reading any Aristotle; however, it is necessary to understand the Scholastic terminology he uses. To aid with this, see:
Philosophically, hylemorphism (the doctrine of actuality and potentiality) forms the basis of Thomism. See:
If you want to read Aristotle (it certainly doesn't hurt in helping one understand St. Thomas), read the following works by Aristotle alongside St. Thomas's commentaries on them: