All theist arguments boiled down to four lines

When "discussing" reality with theists, I have noticed a terrible redundancy in their arguments.  Once you get them to at least a marginally honest position, it ends up devolving into this argument:

• I don't know
• You don't know
• No one knows
• Therefore I know

It's that last one that always bugs me to no end...  How can that even be taken seriously?  And what makes their particular flavour more real than any other flavour?  Why not just accept that "I don't know" is a perfectly good and acceptable answer?  And they accuse atheists of arrogance?  *sigh*