And why does Lutheranism not claim infallibility if it claims to be more truthful than the Catholic Church? Does it claim to have the truth, but is not quite certain it has the truth?
Awesome question! Let me take my Lutheran hat off an answer this personally as an recent Agnostic turned Christian.
Christianity is one of the ‘weakest’ religions - our God was nailed to wood and died, His apostles died in horrid ways, we don’t pray for power and might but for forgiveness, and He offers is His body to eat.
So from the evidence, it may not quite seem rational depending on your upbringing.
Simply, in my estimation you can’t come to Christianity demanding proofs and absolute assurances of truth because if you base your faith on this evidence, you’ll eventually run into a case where reality seen though your intellect and upbringing doesn’t match what Christ tells you: You see bread and wine and Christ tells you it’s his Body and Blood. Or you see a favorite bible verse in Greek and understand that you understood it wrong. Or the pastor didn’t behave pastorally.
So “absolute truth” is not a bulwark for faith, in fact, my
guess is that it can cause harm to faith if you spend too much time in this world and are let down.
Now let me put my Lutheran hat back on…
Lutherans don’t need assurances from the men of the Church - we have our assurance from God. We preach Christ crucified and receive the sacraments.
Finally…and here’s the important bit… If we Lutherans are in error, we invite correction, and would give you thanks.