The Roman cult's iconic scenes: Mithras born adult from a rock, the petra genetrix; the tauroctony, the bull-slaying, around 700 surviving examples; a banquet with Sol. No Mithraic text survives; everything is interpretation of roughly 420 sites, 1,000 inscriptions, and the art. The cult ran seven initiation grades, met in windowless mithraea, admitted men only, and thrived among soldiers from the 1st to 4th centuries. Christianity's rival per the sources, suppressed by the century's end.
The claim that Mithras was born December 25 traces to Franz Cumont, the founder of Mithraic studies, guessing in 1910 that the date might have been a Mithraic feast because it was Sol's, and explicitly warning that our ignorance is absolute. No ancient source dates Mithras's birth or mentions any birth festival. The virgin birth comes from tangled late Armenian and Persian material retrofitted onto the Roman rock-birth. Acharya S assembled the hybrid; historians of Roman Mithraism reject it.
The claim: Mithras became the ideal Jesus-twin precisely because no scripture survives, an empty file accepts any comparison, and the mystery cult's secrecy, its one well-documented feature, is what made it infinitely malleable for later mythographers. Verdict: the evidentiary situation supports it, interpretation is contested because there is nothing to interpret but stone. The bull, the cave, the grades, the handshake, the syndexioi, are real. The rest is projection. The mystery kept its mystery so well that it became everyone's mirror.
If no Mithraic text survives, whose story are the parallels paralleling?