De Pudicitia makes the case that the prohibition on (a) idolatry (b) blood (c) what has been strangled and (d) fornication is everlasting and inviolable. Apparently there were 'others' who argued that Paul forgave even these sins:After they finished speaking, James replied, “Brothers, listen to me. 14 Simeon has related how God first visited the Gentiles, to take from them a people for his name. 15 And with this the words of the prophets agree, just as it is written,
16 “‘After this I will return,
and I will rebuild the tent of David that has fallen;
I will rebuild its ruins,
and I will restore it,
17 that the remnant of mankind may seek the Lord,
and all the Gentiles who are called by my name,
says the Lord, who makes these things 18 known from of old.’
19 Therefore my judgment is that we should not trouble those of the Gentiles who turn to God, 20 but should write to them to abstain from the things polluted by idols, and from sexual immorality, and from what has been strangled, and from blood. 21 For from ancient generations Moses has had in every city those who proclaim him, for he is read every Sabbath in the synagogues.”
22 Then it seemed good to the apostles and the elders, with the whole church, to choose men from among them and send them to Antioch with Paul and Barnabas. They sent Judas called Barsabbas, and Silas, leading men among the brothers, 23 with the following letter: “The brothers, both the apostles and the elders, to the brothers who are of the Gentiles in Antioch and Syria and Cilicia, greetings. 24 Since we have heard that some persons have gone out from us and troubled youwith words, unsettling your minds, although we gave them no instructions, 25 it has seemed good to us, having come to one accord, to choose men and send them to you with our beloved Barnabas and Paul, 26 men who have risked their lives for the name of our Lord Jesus Christ. 27 We have therefore sent Judas and Silas, who themselves will tell you the same things by word of mouth. 28 For it has seemed good to the Holy Spirit and to us to lay on you no greater burden than these requirements: 29 that you abstain from what has been sacrificed to idols, and from blood, and from what has been strangled, and from sexual immorality. If you keep yourselves from these, you will do well. Farewell.”
I think this material has been understood. Yes Tertullian invokes the idea that there are those who say that the Paraclete who was 'in the apostles' (i.e. the community of James) said different things from those - 'the prophets' - who came after them. But the underlying argument which follows in De Pudicitia seems to be a referendum on Paul - i.e. did Paul, the Paraclete (a term from Marcionism cf. Origen Homilies on Luke, Hegemonius etc).But about those, who think there is a difference between that paraclete, which was in the apostles and that, which was working by them, and which, recognised nowadays in their special prophets, they can no longer see in the apostles, now they may show anyhow by means of the scriptures of the apostles, that the commaculation of the flesh and especially stained after baptism can be cleansed by penitence, not, that the form of the old law has been dissolved even in the apostles; and they may not think according to the conception of the criminality of adultery, that this form is thought to be less severe in our new discipline than in the old. When the Gospel was first heard and had shaken the old conception to such a degree, that one began to discuss, whether the old form of the law was to be retained as matters stood, at this moment the Holy apostles, by the authority of the Holy Ghost emitted this commandment,"For it seemed good," they are saying to those, who among the Gentiles had begun with the first things in the law (i.e. circumcision) "to the Holy Ghost and to us, to lay upon you no greater burden than these necessary things, that ye abstain from meats, offered to idols, and from fornication and from blood: from which if ye keep yourself ye shall do well according to the will of the Holy Ghost."
It may be enough to state, that even at this point adultery and fornication have their place of honour between idolatry and homicide. (For as to blood I would prefer to think of human blood.) For how severe must such crimes be regarded by the apostles, which they before all are excepting from that old law as to observation, which they before all decide are to be avoided of necessity? Of course, they do not permit others, but they before all put these crimes as impossible to forgive, these apostles, who have for the Gentiles made the other burdens of the law excusable. Why do you think they are lifting away such a yoke from our neck, if not for ever to impose on us this more simple discipline? Why do they relax so many bonds, if not to tie us for ever to more necessary things? They have absolved us from so many burdens, thus taking us obliged to avoid that which is more pernicious. There has been an exchange made. We have gained much end must offer a little. But it is not possible to cancel this exchange, if of course it is not cancelled by the renewal of this very adultery or homicide or idolatry. For the law is to be accepted in its full extent, if the condition for forgiveness is solved. But the Holy Ghost has not made this bond with us inadvisedly but has made it of his own accord and so it is to be held more sacred. Nobody will annihilate his covenant, if not the ungrateful. And now he will not take back that which he has given away, and he has not given away that which he has reserved for himself. The statements of a last testament are ever prevailing and of course the statement of this decree and this commandment will remain to the end of the world. He has sufficiently refused the forgiveness of such things, which he has elected to be observed, and he has provided for that, which he has not sanctioned in the same way. That is why no forgiveness is given by the church either for idolatry or for homicide. It is not allowed to presume - as I think - that the apostles have made any exception of this statement of theirs; or if someone can presume that, he will have to give proof of it.
We know well their suspicions even about these matters. For in fact they are suspecting that St. Paul, the apostle, has given his forgiveness in the second epistle of the Corinthians to the same fornicator, whom he in the first epistle had said was to deliver unto Satan for the destruction of the flesh, the impious heir of his father's wife, as if he had later on changed his mind, writing: "But if any have caused grief, he hath not grieved me, but in part, that I may not overcharge you all. Sufficient... is the punishment which was inflicted of many. So that contrariwise ye ought rather to forgive him and comfort him, lest perhaps such a one should be swallowed up with overmuch sorrow. Wherefore I beseech you, that ye would conform your love toward him. For to this end also did I write that I might know the proof of you, whether ye be obedient to me in all things. To whom ye forgive anything, I forgive also. For if I too forgave anything, I forgave it in Christ. Lest Satan should get an advantage of us, for we are not ignorant of his devices." [De Pudicitia 13]
Yes the author is using Catholic texts (i.e. Acts, references to Peter in Matthew etc) but the underlying argument that Paul was the Paraclete who contradicted things said by James in Acts is Marcionite.