The question for Christian theologians, and really all the faithful in some ways, is "What does human nature on its own desire?"
For the theologians, the questions are more specific. On its own does it desire supernatural union with God and thus the beatific vision? Or do we need grace to have this desire?
The first is the most self-evident (as an aside, it was decided by some friends and I that it's most self-evident to women, and the nature of males and their spiritual life makes it so that a man had to write it down and then it's deep and profound for everyone to ponder.). St. Augustine famously wrote, "You have made us for yourself, O Lord, and our hearts are restless until they rest in You," in his Confessions. Later Fathers hold this view, which is neatly summed up as at a minimum this world cannot fill our desires. St. Thomas Aquinas also leans towards this view (in one interpretation, which is the correct one. This isn't a story without the weird digressions!)
After St. Thomas, theologians said pure human nature would not seek God sans grace. Some said that pure human nature was a hypothesis that did not actually exist, and for others it was prior to the fall (what about original justice and fallen nature and all that? Hold your donkeys!).
The theologian Cajetan, writing in the 15th century, argued that Thomas argued, correctly, that pure human nature would not desire union with God. This was at odds with the interpretations in the century following the life of the Angelic Doctor. For about five centuries, culminating with the work of the spiritual master Reginald Garrgiou-Lagrange, other theologians tended towards this view. No one disputed that the Common Doctor was right though. And that's where it gets interesting.
To be continued...