Lol…yes we are back to the beginning. Actually that the church “always believed in Mary ever virgin” is a much more definitive claim than mine, and if I recall “debate/discussion” protocol, the burden of proof is on you. As to my stand, it basically challenges yours, or as I subsequently posted, if one assumes it was taught, one can assume the contrary was taught…both are assumptions out of “silence”…no direct evidence, only hearsay. I agree with those that say this dogma obviously developed which does not deny that at some point it began to be taught, probably first by some, to later by all, or finally embraced as dogma for all.
Where I make a less definitive claim it is saying that it is possible someone taught it from the beginning, but that it was not eveyone, or an apostle, and certainly not the church as whole. That is, it was not taught universally like all the other doctrines we agree on.
So we have Jerome in latter 4th century, being explicit, and you say you found an earlier writer, maybe latter 3rd century(still have to look back to your post on that), and you have Jerome saying earlier writers would also attest to doctrine but have no writings to back that claim, making that hearsay (save for the one you claim you found), and understand Mitaka post that perhaps these writings were lost that Jerome referenced, to which I add we may have also lost any writers claiming a contrary doctrine, such as Helvidius writings.
From the other direction we have nothing explicit from scripture, and no hearsay that apostles taught it.