Excellent! Thanks for the explanation - I'd sort of thought it was something like that.
From a lay standpoint, the common explanation is that atheists are sure there's no god, but agnostics aren't that sure. The point I had was that, technically, if one is of scientific mind, one can't be totally sure there is no god - tentativity must be maintained.
I'm not sure that's necessarily the case. I'd say more likely it depends on how each individual assesses the "confidence level" of their epistemology or worldview.
I'm a pretty solid atheist, all things considered. From my standpoint religions have had literally thousands of years and literally millions of adherents searching for or at least interested in uncovering factual evidence of the existence of God or gods. In spite of all that effort, to date no such evidence has been unearthed. It is therefore quite reasonable to assume no evidence exists - and therefore god(s) doesn't/don't exist. Is it an assumption? Yes, of course. Is it unwarranted? No.
This is quite different from a "belief" that abiogenesis has occurred, for instance. While there hasn't been any objective "proof" uncovered yet that it did, there are multiply-converging lines of evidence that give clues that it
could have occurred. It certainly doesn't appear to violate any known natural laws or processes and can be reasonably postulated from known phenomena. Unlike, for example, an invisible, undetectable, unknowable super-entity.
So whereas the statement "there are no gods" may be unsupported at the most fundamental logical level, it isn't unreasonable considering the vast amount of time and resources that have been unsuccessfully sunk into trying to find evidence for their existence. Could there be gods? I suppose anything is possible - just like quantum physics leaves open the possibility that my car might translate overnight from the garage to the street. However, the probability of this occurring is so vanishingly small that it is effectively zero. I'm not gonna hold my breath...
I've gotta head to a meeting. I'll try and post more later on this.