Hey TTWSYF
I'm just asking for a basic standard of evidence. I'd accept that the writer of Matthew was claiming a church existed in Jesus' lifetime if he weren't using the future tense when describing it. One would think that establishing a church would be a major part of Jesus ministry no other gospel writer would have missed. Kind of like angels turning up to his birth, or when he was born, or when he died, or what happened when he died, and what happened when he came back... Actually...
Anyhow, Mark surely would have mentioned it (earliest canon gospel). You'd think the writer of John would. The writer of Luke claims he's a historian, surely it would have been of interest? The whole point he says he's writing a gospel is to cover bits other gospel writers (of which we know of a few dozen) haven't mentioned or have got wrong (Luke 1). It's a huge thing in Acts 2 (v.42 on) when he starts describing the 'fellowship'. In fact, that seems the closest thing to an origin story for christian churches...
Multiple sources better than single source. Multiple sources agreeing on basic facts better than mutiple sources disagreeing over them.
If Matthew uses future tense, then the claim that Jesus established a church in his lifetime can't be proven by that statement. That's basic reading comprehension. If we can't agree on something as simple as that, then we're obviously going to struggle to do more than talk past each other. We're both entitled to our opinions, but we do have to share the facts. :) I have absolutely no idea on Jesus' intentions, sorry. It would seem that even those who say they followed him round for years didn't either, as they seem to have been expecting him to return and smite the wicked and died without that happening.
So by saying to Peter he's a rock and something will happen in the future, a church is established by Jesus in his lifetime? Doesn't really work for me. I can see where you're coming from, but saying for the future isn't making it so in his lifetime.