I will speak from my own experience:
When I drink a little - I want more, nothing will come in the way of that and there is now way to tell when I will stop (last times I have ended up in the hospital). In AA we refer to this as an allergy to the substance of alcohol which produces a craving for more. Like if you were allergic to strawberries and you break out in a rash when you ate them, there is no way to use will power or knowledge to stop that rash. My 'rash' is craving - I drink more. 1 drink turns into 'x' amount of drinks (I don't know when it will stop). This is strictly a physical thing -
So my option is to leave alcohol alone.
So I go to three rehabs, learn a lot about alcoholism, its affects on the body, triggers, meetings, sponsors, the book...and I stopped drinking.
That lasted 14 months - then I drank again and I have absolutely no explanation as to why. All the knowledge of what taking that drink meant, never came to mind. What a freak I feel like. I just picked up a drink and that craving started again, it was worse.
A body that cant have it and a mind that won't stay away.
That is my definition of an alcoholic. There are many that abuse alcohol, but they can stop if something important enough comes up (threat of jail, etc).
Then I go through the AA big book with a man who has recovered from alcoholism and I see that the people who wrote that book had the exact same experiece as me
phhewww - I am glad they had an answer and live that answer day to day.