[Man of the Old Hope]

So it was predestined that good (Eru's will) would prevail. And it was the exercise of free will (assisted by Eru's guiding hand) that brought this about.

The Saucepan Man's summary is pretty much in line with the Roman Catholic understanding of predestination (consult the Cathechism of the Catholic Church for particulars), which, for all his knowledge and use of (especially) northern European mythologies, would be the greatest influence on Tolkien's conception of Eru Iluvatar's providence.

And while Osse is correct in the statement about "angelic powers" (the Valar are very much like the pantheons seen in various religions - though for my money, far more interesting - perhaps this is how a Christian would construct a pre-Christian "paganism"?), Iarwain's understanding of Tolkien's Catholic (Christian) particularism contra the theological pluralism suggested by Osse is also correct, as seen for example in any number of Tolkien's letters now in published form.