St. Augustine explicitly says here that those who are outside the Church can still have Charity. Thus they are justified, and are united to the Church spiritually by that Charity. Because he says “may come after all, as it were in the evening, and be brought into the one communion by the mouth of the dove in the kiss of peace,” it is evident that he is not referring to people who at the moment are desiring to enter the Church. Thus someone can be spiritually united with the Church, even if he does not actually desire at the moment to be united.
This passage leaves open the possibility that those who do not even know Christ and/or hold many heresies may have charity, since St. Augustine does not exclude the possibility of an infant being baptized outside the Church, and then being raised without knowledge of the Church.
Here is another passage which again says the same thing:
“There are some also who as yet live wickedly, or even lie in heresies or the superstitions of the Gentiles, and yet even then "the Lord knoweth them that are His." For, in that unspeakable foreknowledge of God, many who seem to be without are in reality within, and many who seem to be within yet really are without. Of all those, therefore, who, if I may so say, are inwardly and secretly within, is that "enclosed garden" composed, "the fountain sealed, a well of living water, the orchard of pomegranates, with pleasant fruits." The divinely imparted gifts of these are partly peculiar to themselves, as in this world the charity that never faileth, and in the world to come eternal life; partly they are common with evil and perverse men, as all the other things in which consist the holy mysteries.”
Notice that he says here that those who lie in heresies or the superstitions of the Gentiles can seem to be without, yet in reality are really within, because they possess “the charity that never faileth.” Again, he implies that even those without an explicit faith in Christ may yet have charity, since presumably one kind of “superstition” of the gentiles, or heresy would be to not have faith in Christ as God.
Here is another passage of St. Augustine which is related to these, and to the doctrine of “extra ecclesiam nulla salus.”
“The Apostle Paul has said: 'A man that is an heretic after the first and second admonition reject, knowing that he that is such is subverted and sins, being condemned of himself.' But though the doctrine which men hold be false and perverse, if they do not maintain it with passionate obstinacy, especially when they have not devised it by the rashness of their own presumption, but have accepted it from parents who had been misguided and had fallen into error, and if they are with anxiety seeking the truth, and are prepared to be set right when they have found it, such men are not to be counted heretics.”
St. Augustine says here that someone who holds false doctrines because he has accepted it from misguided parents, but who nevertheless are open to the truth should not be counted as heretics. In other words, such a person is implicitly a Catholic and is within the Catholic Church, even before they have given up their heresies. This has significant implications for those who hold to the strict view of EENS.
We read in the council of Florence that “It firmly believes, professes and preaches that all those who are outside the catholic church, not only pagans but also Jews or heretics and schismatics, cannot share in eternal life and will go into the everlasting fire which was prepared for the devil and his angels, unless they are joined to the catholic church before the end of their lives.” This passage is often quoted for those who hold to a rigorist interpretation of EENS. However, notice this: The council of Florence includes heretics as those who will go into the everlasting fire. As St. Augustine points out, though, not everyone who holds false doctrine is accounted a heretic. If someone is not obstinate, and is open to the truth, even though he has received false teaching from his parents, he is not a heretic. Thus, just as we make a qualification in regard to heretics, more generally we also have to qualify who is outside the catholic church.
Incidentally, those who think that there is a contradiction between the council of Florence and what St. Augustine says here, and say that St. Augustine erred in his opinion, are implicitly saying that St. Augustine was damned, since if he erred, he was to be counted a heretic, even if he was open to the truth; and thus, according to such people's reading of the council of Florence, St. Augustine departed “into the everlasting fire.”