I argue that it is entirely irrational.
We are creatures who are first and foremost rationally intent on survival.
Yet we ingest a substance known to endanger our survival, known to have both short and long term negative consequences - even after many and prolonged direct experiences of negative consequence.
Any other threatening of dangerous experience we have in life leads us to avoid like situations in the future - yet we go back to alcohol time and again even after near-death experiences with it.
Further - our science doesn't even know quite how or why alcohol does what it does. We know that it changes the very structures of the brain and body at a cellular level but after much research we don't even know what the hell it is and why it works.....
So an organism whose primary priority is survival willingly endangers its own survival by repeatedly consuming a substance of unknown function and impact despite repeatedly encountering its terrible, survival-threatening effects.
This is not in keeping with logic or reason.
This is irrationality, insanity illustrated.
http://m.psychologytoday.com/blog/yo...-brain-alcohol