Denis, the english word you are maybe looking for is 'agnostic' - an atheist has a belief, as you say, even if it is a 'denial belief', but an agnostic simply does not know, and is happy to admit it

good philosophic point about 'not believing' not being the same as 'lacking a belief' - 'lacking a belief' being the viewpoint of someone who believes, which someone who does not believe doesn't have.

but maybe lost a bit of impact and clarity due to english not being your first language .... [and difficult to get clear even when it is ]

and possibly not what Grace intended