Are you implying that 100% certainty is impossible? I think not, right? I mean when Paul finished Romans, did he release it with the disclaimer, "Not really sure all this stuff is true, but I sure hope it is!"
Next question. Is God a respecter of persons? Paul was probably 100% sure of his salvation - and I'm consigned to, say, 99% certainty? Wow. That stinks. Maybe I can rephrase the problem here. When we evangelize, we are counseling people on their eternal destiny. You see the problem, don't you? Why would God want His ambassadors - His supposedly professional evangelists - to advise an unsaved person on his eternal destiny if they themselves are uncertain about eternal destiny? Doesn't make sense. Right? I mean, let's be honest, meaning, let's be honest with the unsaved person. That is to say, since you believe the evangelist is only supposed to walk in, say, 99% certainty, then you should evangelize like this:
"Hi my unsaved friend. Here's some advice about Jesus. But take it with a grain of salt, because I'm not completely sure it will get you saved. I'm not even completely sure that I am in the correct religion."
In fact, that's how I currently speak to unbelievers, if they ask me about my religion. I'm totally honest with them - honest about the fact that I am not 100% certain.
Now here's the problem. When I read the book of Acts, I see no evidence of such honesty - no such disclaimers. Rather the apostles talked like this (to paraphrase).
"Repent, and accept Jesus as savior. Otherwise you are doomed to hell."
I see two options here:
(1) Perhaps I am more honest than they are. I am willing to hedge my words with disclaimers, whereas they were too dishonest to admit their uncertainty.
(2) OR, perhaps they preached with 100% certainty.
Now, as I've demonstrated earlier, NT evangelism is defined as prophetic utterance. Given the very gravity of prophecy, I think #2 is a safer bet.
See what I did? I argued my position. I didn't just assert it, fronting the assertion with a series of personal attacks.