Sometimes, there is so much material on Step One in the Big Book that you can't see the wood for the trees. It is also difficult to sum up Step One by posing negative questions, e.g. 'are you certain you can never drink safely again' or 'are you certain you could not stay sober without AA'.
It is more helpful to pose the questions positively.
'Are you certain that you could drink moderately for the rest of your life?'
If you are not certain, you had better stay sober.
'Are you certain you can stay sober for the rest of your life without any help?'
If you are not certain, you had better seek help.
One cannot prove that one could not stay sober without AA; after all, there are cases of people who go to AA for a while and then do indeed stay sober in perpetuity.
The question is rather: are you confident enough in your ability to moderate or stop on your resources that you're willing to take the risk?
I am not.