Using the varieties of positions of what god is...
However, I must note pantheism due to this not actually fitting in with the rest.
What does pantheism do?
It utilizes our incessant need to label things due to the way we structure thoughts.
Pantheism is intellectually dishonest and still fuels support to the god delusion, so it needs to be trashed with he rest.
So, saying 100% positive there is no god in respect to pantheism or Buddhism doesn't make sense. They are conceptualization tools, with the former lacking proper documentation.
In regards to the whole "even water can only be purified to 99.999999999 %" spiel...
This is not the same thing as 100% positive/certainty.
If one is 100% certain they can hold a dozen grenades as they explode and live,
that is still 100% positive regardless if they die or not.
Research into the neuroscience of belief will assist with understanding.
How could anyone doubt the existence of the ONE TRUE MONOGOD, all THREE (Trinity) of HIM?
(Sarcasm mode off now)