For we do not receive these things as common bread or common drink; but just as our Savior Jesus Christ, being incarnate through the work of God, took flesh and blood for our salvation, so too we have been taught that the food over which thanks have been given by a prayer of the Word that is from Him, from which our flesh and blood are fed by transformation, is both the flesh and blood of that incarnate Jesus. (First Apology 66:2)
I ran across this statement from Justin Martyr in the 3rd Century, and it occured to me that in all of my reading of primary sources throughout church history, I can’t find a single person who regards the elements of the Lord’s Supper to be merely a memorial or a symbol prior to the 16th century who isn’t also a heretic for other reasons. If it is in fact true that the memorial view wasn’t held by any otherwise-orthodox believer prior to the sixteenth century, what does this say about the validity of this view if no one in the church holds to it for fifteen hundred years of the church’s history? Was the whole church wrong until Zwingli? I suppose many Evangelicals will bite the bullet and say yes, but that’s an awfully big bullet. Let me head off at the pass the argument that the Roman Catholic church is to blame for this doctrine. Sorry to take away from you that old saw, but the doctrine of the real (and unique) presence was in the Eastern church as much as it was in the Western church. Long before the Magisterium in the West, the church throughout the world held to this doctrine. Ultimately, to hold a memorial/symbolic view is to disconnect yourself from the church throughout time.
Note: this question should be asked about other doctrines too, but lots of doctrines pass this test. There were a variety of views on baptism throughout history for example, and justification by faith alone (even if in nascent form) can be found much earlier than Luther.