I must admit, I have been struggling with this one, bamboo. But when I think about the differences between my family and my own drinking and my ABFs, I am starting to accept there is a definite element of disease.
My family barely drink, and I was not raised around drinkers (I am very grateful for this now!), nor have I ever gravitated towards big drinkers. When I met ABF, this changed as his family are big drinkers (his brother and estranged father are both alcoholics) and so are the majority of his friends. There is a definite cultural component as well. This was a big shock for me, but I thought maybe these were once off drinking sessions, and that I had just been sheltered and was over-sensitive (at least, that's how he made me feel). This is the nurture part, and being around him even made me drink more (again, nurture) for a while until I realised his drinking was a problem.
The nature part is that he shares genes with his father. I know this must be genetic as I very much feel my limit when I drink. I have a few (lightweight) and I fall fast asleep. I don't get aggressive or depressed or anything like that, I just fall asleep. I could probably try to force a few more drinks into me if I really tried, but it would be extremely difficult and unpleasant. ABF, on the other hand, doesn't have that switch. He was drinking continuously for days at a time without sleep, going through fits of aggression, depression, hysteria... It was frightening to wake up and find him still drinking. And confusing. In contrast to me, trying to force himself to STOP drinking was what was extremely difficult. Obviously he's a lot bigger than me, and has grown up drinking heavily so has a tolerance, but I still really struggle to understand how such drinking is physically possible.
And I think this is what makes it a disease. My (slow) realisation of this is what is helping keep my great build up of anger from past hurt in (reasonable) check, and makes me understand why one sip could spell the end of his sobriety. It also makes me feel really sad for him.
I hope this made a bit of sense.