“Whatever the precise definition of the word may be, we call this plain insanity. How can such a lack of proportion, of the ability to think straight, be called anything else?” (Page 37, Big Book)
Imagine a forest where wayfarers encounter lions. The lions are very powerful and eat wayfarers. Now imagine that wayfarers typically go mad when they see a lion and stick their head in the mouth of the lion, which eats them. You might conclude that they are getting eaten because they are mad. However, some wayfarers are immune to this madness. When such a wayfarer encounters a lion, he runs, but the lion always catches him and eats him. The bottom line, it turns out, is that the wayfarer will get eaten come what may. The madness is usually there, but is merely an accompanying phenomenon, something that is merely making the job easier for the lion. But the lion will get its way.
So with alcohol.