When St. Augustine and Aquinas made it clear that it was okay to reason and believe in the theories of ancient Greek philosophers, while still being a Christian, it changed the lives of many individuals living during the Middle Ages. People’s knowledge that they could believe in what Plato and Aristotle had theorized, while still maintaining their belief in God, basically answered the main medieval philosophical question.
St. Augustine thought he was a totally Christian man, yet he wanted to practice using reason. I believe it is for this reason that he merged Platonic philosophy with Christian views, in order to maintain his faith, but learn about the world in whatever way he pleased. Had the Christian or Platonic views on how the world was created been different, it is still likely that St. Augustine would have found a way to allow them both to be true, in my opinion. I also believe that St. Thomas Aquinas christianized Aristotle for the same reason, simply to still be a devout Christian without giving up his philosophical views.
These revelations were highly significant for all Christians that were interested in philosophy, or were purposefully ignoring philosophy in order to maintain their faith. Had Aquinas and St. Augustine believed that you could only believe in either the theories of the ancient Greek philosophers or God, all of history could have been changed. The philosophical theories of Plato and Aristotle could have simply been forgotten in history because all of the Christian population could not have agreed with or tried to understand their views on philosophy.
Fortunately, since Augustine and Aquinas felt the way they did about the two beliefs coming together, the theories of Aristotle and Plato have been carried with Christianity into the present. People can ponder and discuss the theories to this day, and decide what side to agree with on certain issues, if St. Aquinas or St. Augustine never found a suitable answer as to how both sides could be possible.
Conclusively, since St. Augustine and St. Thomas Aquinas were able to tie together the belief in Christianity and the theories of Plato and Aristotle, everything about the two ancient Greek philosophers can still be studied today. Who knows, had all of the Christian population not been able to learn about their philosophical theories, anything else the two of them thought might not have still been around to study today either. Regardless, I believe that St. Augustine and Thomas Aquinas had a positive effect on the philosophical and Christian worlds.