Faith and reason
There is a central dilemma in Aquinas's writings, because the dilemma is central in every element of his life, which we learn through his letters and commentaries—the dilemma between faith and reason. Is reason a sufficient method for examining reality or for imagining about God? For Thomas Aquinas, this question is an immensely difficult one to parse, but in his attempt to extricate the emotional faith from its mental counterpart, the ability to agree with truth through scientific inquiry—that's where his writing comes from. It's all his attempt to discern what can be known.
God and logic
Aquinas is deeply religious, as he admits boldly, and which he defends in many of his writings, but he does predicate his arguments on this fundamental axiom of his worldview—that one can know God by reasoning through the questions about his existence, trying to maintain some kind of objectivity in the meantime. Aquinas is not perfectly objective, but for his time, his point of view represents a kind of intellectual humility, because he considers himself a slave to his ability to think clearly. This is not unlike Averroes.
Debate and teamwork
The heart of scholasticism is not to endlessly debate, but rather, one wins through disputio which simply means, through discourse. Just like Western law is predicated on a debate (typically the debate of trainer lawyers) and judgment, so also, Western philosophy is predicated on combat between minds through rhetoric. Aquinas's writings are the prized possession of this point of view, and his Summa Theologica, his Summa contra Gentiles, and also, his commentaries on Aristotle have been viewed as among the most powerful thought ever demonstrated in these methods.
