The fact that Paul condemns (in quite strong language) a system of teaching that contained something in common with full preterism, does not condemn full preterism. It is more likely that Paul is condemning gnostism which was, in the middle of the first century just beginning in Christian circles but blossomed into maturity early in the second century and resulted in the Nag Hammadi library of documents.
Paul was apparently quite sensitive about the topic of the resurrection because he spends most of 1 Cor 15 (with quite strong language) developing the doctrine in great detail It is unsurprising that he condemns people who opposed it because it impinges on the centrality of Christ and His resurrection: Christ's resurrection is the firstfruit (1 Cor 15:20, 23) of the great resurrection; and, Christ's resurrection enables the great eschatological resurrection.
Now we should immediately recognize that perfect understanding of theology is NOT a prerequisite for salvation - nobody, no human, has a complete or perfect understanding of such. Therefore, a complete and perfect understanding of the Bible and Christ is not essential for salvation. The matter in this question is how a misunderstanding of the resurrection affects the doctrine of soteriology to such an extent that it makes people lose their faith.
Ellicott writes this:
These early Christian followers of men like Hymenæus and Philetus had
much in common with the ascetic Jewish sects of Essenes and
Therapeutæ, and especially with the famous Sadducean school, which
attracted then so many cultured and wealthy Jews. They opposed, to use
Van Oosterzee’s words, “their own sickly idealism to St. Paul’s strong
and healthy realism.” Death and resurrection, with these early
opponents of St. Paul, were terms which had only a spiritual meaning
and application. As Waterland puts it, “They allegorised away the
doctrine, and turned all into figures and metaphors.”
We do not have any extant record of exactly what these early heretics, Hymenaeus and Philetus, were teaching. As stated above, there are other theologies that deny the resurrection. In any case, the problem is not the teaching itself as the effect on the adherent - denying the resurrection and making the person lose faith in Christ. Anything that has this effect should be condemned.
I am a little glad that we have no records of what Hymenaeus and Philetus were teaching - it does not matter. The important thing for us today is concentrate on what the Bible does say and not what it does not say. In the words of Isa 8:20 -
To the law and to the testimony! If they do not speak according to
this word, they have no light of dawn.
The doctrine of the resurrection is amply attested in Scripture and that is enough for me. Paul's teaching in 1 Cor 15 is clear and is consistent - see appendix below for a summary.
APPENDIX - Resurrection
The Bible teaching on this can be summarized as follows:
- The source of our eternal life at the resurrection is Jesus and His resurrection. 1 John 5:11, 12, 11:25, Rom 1:4, 6:5, 1 Cor 15:12-21, Phil 3:10, 11, 1 Peter 1:3, 3:21, etc. See also Jesus’ Resurrection.
- The resurrection of the dead will occur at the end of time when Jesus returns. Matt 22:30, 31, Mark 12:23, Luke 14:14, 20:33-36, John 11:24, 25, 1 Thess 4:16, 17, 1 Cor 15:21, 22, 46-55.
- There are two resurrections – one of the righteous and the wicked. Rev 20:5, 6, John 5:28, 29, Dan 12:2, Acts 24:15, Heb 11:35. See also Rev 1:7.
- People receive their rewards at the resurrection, Luke 14:14, Rev 22:12, 13.
- The righteous receive real, imperishable bodies at the resurrection, albeit different from what we have now; 1 Cor 15:35-54.
- People are “sleeping” in the grave until awakened by the resurrection, Acts 2:29-31, 34, Matt 9:24, Mark 5:39, Luke 8:52, John 11:11, 12, Acts 7:60, 13:36, 1 Cor 11:30, 15:6, 18, 20, 51, 1 Thess 4:13-15, 5:10, 2 Peter 3:4, Ps 17:15, etc.
- The teaching about bodily resurrection is also found in the OT; Job 19:25, 26, Isa 26:19, Dan 12:2, 13. See also 1 Sam 2:6, Job 14:14, Ps 17:15, 49:15, Hos 13:14 (which is quoted by Paul in 1 Cor 15:55).
