They claim that an doctrine can only be infallibly defined if it's been believed in all places in all times.
The Vincentian canon, the teaching of St Vincent of L+Ãƒâ€šÃ‚Â¬rins, the watchword for 'sound' orthodox catholic types - semper et ubique et ab omnibus
. Always and everywhere and by all.
But who believed in the Immaculate Conception before the visions that started that movement?
The Byzantine Rite calls her immaculate, but the origins of the IC go way back to the Middle Ages, long before the 'visions'. Theologians Paschasis Radbertus and John Duns Scotus came up with it, inferring it from the tradition about Mary's purity and also from particularly Western Catholic theology about original sin from St Augustine.
But as for the Trinity, the Liturgy, the Eucharist, the Nature of Christ, while their expression developed and became more precise over time, I firmly believe that these doctrines were taught by Christ in the 40 day period between the Ressurection and the Ascention when He taught the faith to the Apostles before thier ministery started at Pentecost. We still pray the Liturgy of St. Mark, and there doesn't seem to be any deficite of theology compared to the Liturgies that came after the councils. The precise statement of doctrines progressed, but never were new doctrines developed as the Catholics claim.
Well, I don't think they knew it in exactly
the form enunciated by the Church at the councils much later, but of course that doesn't mean those things aren't true - the fact that all the 'Catholic' (ancient, apostolic) churches believe in these things says something.