St. Thomas says that the revelation of the Trinity destroys certain errors about creation, most of all the error that creation was necessary. What does this mean?
Without the revelation of processions in the divine nature, as far as we know the first procession is the procession of creatures from God. This procession would have to be either necessary or not. If necessary, creation would have a certain equality to God (for creation would be just as eternal, imperishable, subsistent, and permanent as God himself); but if free, it could not be an imitation or participation in any prior procession, and so it would be absolutely arbitrary. The first position was that of the Latin Averroists, the second seems very much like the common Islamic position about creation.