“Or perhaps he doesn’t think at all.” (Page 24, Big Book)
The impulse to drink is normally accompanied by an insane rationalisation.
But sometimes one knows exactly what one is doing it and does it anyway: there is no mental insanity at play.
And sometimes there is no thinking at all: there is no mental insanity at play.
The behaviour is indeed insane, as it were a behavioural insanity, but is not prompted or even enabled by insane thinking, either because such thinking as there is is not insane or because there is no thinking at all.
Most of the time, a resumption of drinking is due to the duo of compulsion plus mental insanity.
But when the mental insanity is not present, one realises that the compulsion never needed its sidekick, the mental insanity. It was always perfectly capable of doing the job on its own.