Do people who believe in only a finite existence and that there is no type of 'after life' ; do they think this is an absolute certainty ? If one is extremely certain about this being a 'finite existence' yet there are no convincing arguments for this then it can not be an absolute certainty. ( Note: 'believing' in something implies some doubt is possible in that 'something' being true and yet the person ,however is maintaining the belief.) In other words do those who think life is 'finite' believe this is a certainty even though there are no clear arguments that can demonstrate this??
This question appears to be asking about believing in the absolute certainty of something; and in this case specifically about those who believe in a finite existence; and he's asking whether absolute certainty is somehow question-begging; or in his own words 'inconsistent' when using the word 'belief' at the same time.
After all many academics question the assumed certainty of belief that theists use; so why not question the certainty for those who believe in a finite life?