But if you begin from unaided reason, the double-predestination doctrine can be seen to be unreasonable.
So there is a paradox. The conclusion derived from First Principles of natural reason apparently contradicts the conclusion derived from certain Scriptural passages. Where does a Christian go from here? The Catholic would defer to unaided reason, since conclusions derived from First Principles are known with certainty. Therefore, the Catholic would conclude (based on the belief that the Bible is inspired) that the Scriptural contradiction is an apparent contradiction or paradox, since Reason cannot contradict Faith (since God is the author of both).
The Catholic would then look to the Church's teaching on the matter or the Church's infallible interpretation of Scripture. With regard to the passages frequently cited by Calvinists which say that "God hated..." the explanation is that the phrase "God hated..." is a Jewish idiom with a different meaning than what we would ascribe to the phrase.
It also proceeds from unaided reason. In fact, the first thing obvious to man about God is his power; his love can be naturally put into question, as many Old Testament episodes illustrate.
Are you saying that Paul misunderstood the Jewish idiom? He did write in Greek, right? (I'm not a Calvinist, in the interests of full disclosure.)