If any one saith, that the grace of Justification is only attained to by those who are predestined unto life; but that all others who are called, are called indeed, but receive not grace, as being, by the divine power, predestined unto evil; let him be anathema.
The Council here condemns three errors: first, that only those who are predestined to life receive justification; second, that the rest of humanity receives no such grace; and third, that these latter are predestined for damnation.
The first of these errors contradicts the fact that we do not know (because God has not revealed) who are among the predestined; we do know (generally) who has been justified, inasmuch as justification is received through the Sacrament of Baptism, but the warnings against apostasy in Scripture make it clear that not all who are baptized will be saved. Consequently it is impossible for the two groups (the predestined and the justified) to be the same.
The second error goes hand in hand with the first; the presumption behind it is that those who receive the grace of justification must inevitably be saved, but this is false.
The third error hardly needs comment. The Catholic Church teaches no double predestination.
As we see, justification by grace alone is not condemned here.