What explanation does he give us for his action?

I believe you're refrring to the way John leads his life..... his drinking, smoking, and lack of concern for other people? John attributes his actions to living life to its fullest, as his view of living life is so limited and oppresive that he doesn't see it worth living anyway. John also blames his actions on growing up in a family that is for no better term ..... dysfunctional. His parents have so many problems of their own that they can't even begin to understand his..... nor have they tried.