Commenting on the Last Judgment scene in Matthew 25, St Augustine confronts head-on the false theology which says that faith alone is sufficient. When examining that scene, he points out that Our Lord charges the condemned "with having failed, not in faith, but in good works."
He does not rebuke them because they have not believed in him, but because they have not done any good works. For assuredly, lest anyone should promise himself eternal life by reason of his faith (which without works is dead), He went on to say that He would separate all nations, which before had been herded together, and were accustomed to use the same pastures... These [condemned] had believed in Him, but had not taken pains to do good works, as though they could achieve eternal life by means of that same dead faith.Notice how our holy father among the saints characterizes the understanding of faith alone, or faith without works. He says that it is "dead faith." Living faith, however, is what Our Lord desires; and it is that faith which attains eternal blessedness and grants us the beatific vision. This living faith is active in love; in fact, the two are inseparable. For to believe in God is both to love Him and to love Him in others.
St Augustine indicates that this is the point that not only St James, but also St Paul also makes when he says, "Though I have all faith, so that I could remove mountains, and have not charity, I am nothing."