It's called "evidence". Most evidence for something falls short of a "smoking gun". The idea that one always needs a "smoking gun" to prove something, is at best misleading, at worst a total red herring.
If I see you walking down the street in the opposite direction from the grocery store with a grocery bag from that grocery store in your hands, it's an entirely reasonable inference to say "you just went shopping". However, there's still no "smoking gun" (maybe it's just a coincidence? you brought the bag from home to the gym, it has your swimsuit and towel in it, and the gym just happens to be on the same street as the store? etc). But I don't care that there's no "smoking gun", I'm going to draw the most reasonable conclusion, that's how humans work, you see.
In this case, what we have is (1) Czech intelligence saying that Atta met with Iraqi intelligence in Prague, with corroboration, and (2) absolutely NO contradictory information whatsoever. Seriously, the FBI has issued a lot of pseudeo-denials ("we can't confirm it") but NOTHING which actually contradicts Prague's claim. The most reasonable inference to draw therefore is that Atta indeed met with Iraqi intelligence, unless/until we get information to the contrary. The most reasonable inference to draw from that, given that Atta was the 9/11 ringleader and was a nobody outside of his 9/11 plans, is that the meeting had something to do with 9/11 (what were they discussing? soccer? recipes?). Again, this is the most reasonable thing to conclude from this fact-set, unless/until some contradictory inference surfaces.
It's not a "smoking gun", but there rarely is such a thing, particularly in intelligence about secret things. If we waited for "smoking guns" before drawing conclusions about anything, we'd be paralyzed.
There's no "smoking gun" that Michael Jackson is a pedophile, does that mean you'd allow him to babysit your children?
Now read the "confirmation": 'A Hamburg Student'
Gentlemen, that is weak. That may be another bit of evidence, but it is not confirmation. BTW, I am not denying that there is a link, Peach states an excellent case, one which I agree with.
Had the headline said: 'Evidence of 9/11 link to Iraq continues to mount'
I would have had no problem. But the headline is misleading, which was my point.