Like the third precept about sensual misconduct, this is another of the precepts that generates a lot of interest, both in myself and among those in my peer group. It seems most obviously to be an admonition against substance abuse (be that substance alcohol or any variety of other intoxicating substances). Moral guidance with regard to intoxicating substances does rightfully belong with this precept, no doubt, but I see a subtler and broader view as well.
As with the other precepts, I find a rule-making view such as "don't drink alcohol or do drugs" to be too rigid and easily grasped, though that can be regarded as good advice. On one hand, I like a drink now and again and I haven't found enjoying such to be a moral quandary, neither for myself nor for many of my friends and acquaintances. I've even enjoyed a modicum of recreation and relaxation via intoxicating substances with and in the company of people whose religious practice and sense of moral awareness I deeply admire, and I still do from time to time.
On the other hand, I have also known many people whose lives (and often the lives of those around them) have been literally destroyed by the abuse of intoxicating substances. At the same time, it has not escaped my notice that I've also seen similar destruction waged by means of intoxication with work, with various avocations, with excessive religiosity and by excessively ardent political views. I've seen people do real harm because of being dangerously intoxicated with Buddhism. I suppose one could even get dangerously intoxicated with the precepts themselves.
Welcome to human life. This is the mushy and dynamic netherworld in which we find ourselves with regard to this and every other moral question. One intoxicating notion that I think it is very important to disabuse one's self of is the notion that there are moral absolutes. There are none, not even that one.
The word intoxicant contains the word "toxic." I think that's the point here. For example, in my practice as a nurse I've been ardently drilled in the awareness that every single pharamcologic agent that I administer, no matter how life-saving and comfort-inducing it may be in the proper dosage, can also kill if administered by the wrong route, in the wrong dosage, at the wrong time, for the wrong reason, or to the wrong patient.
That is, there is no absolutely safe substance, not even water itself. You can kill someone with too much water, you can arrest someone's heart and breathing with too much oxygen. One can save a life with a single administration of a single drug one single time, and one can give the same drug in the same dosage to another person at the same time and end their life. That is, there are no pharmacologic absolutes either. Every drug is potentially a poison.
Similarly, every idea, every construct to which one can grasp, is potentially intoxicating. I read Tricycle magazine, an American magazine aimed at Buddhists. Periodically, they will run some recipe for something seemingly wholesome and innocuous like chicken soup. Inevitably, in the very next issue there will be some outraged letter to the editor demanding an apology, that they cease associating themselves with Buddhism, a immediate retraction of the recipe, or at the very least reminding them that an action like publishing a chicken soup recipe is tantamount to torturing innocent animals solely for the satisfaction of one's own selfish, misguided desire for a warm, savory broth.
I suspect the editors publish these recipes and the resultant letters for their amusement (I certainly find them amusing). They usually remind these outraged readers intoxicated with vegetarianism that the Dalai Lama eats meat (which contains the intoxicating notion that this is some official Buddhist imprimatur for meat-eating, but that's neither here nor there) in their editorial reply. I imagine (but do not know) that there are people out there who have summarily canceled their Tricycle magazine subscriptions over a chicken soup recipe. As a see this precept, this action would be a violation of it.
Similarly, there are people on very limited incomes who will miss their rent payments next month because of a first-of-the-month bender when the social security check arrives. This is also a violation of this precept. I know of a pastor in a small Baptist church in Texas who dismissed his own niece from the congregation and from further association with his immediate family because she admitted to seriously considering a premarital affair. This banishment is also a violation of this precept.
In each of these cases, someone attached themselves to a notion or an experience so tightly that they caused harm. Toxins cause harm. The fundamental moral guidance for me in my life is to live for the benefit of all beings (NB: I did not say "all other beings"). This seems wholly consistent with my direct experience of Reality. Harmony is our natural state of existence.
So, what I think the use of the concept of intoxication in this precept points towards is this notion that when there is something that when present in some measure may bring some comfort one must be careful. This very same thing, be it bourbon, vegetarianism, or Buddhism, can also be indulged in to the point where it becomes poisonous and harmful. The problem isn't out there. Addiciton is not dissolved in bourbon, it is contained within the mind. Intoxication is not non-tee-totaling. As any honest student of a 12-step program will tell you, a dry drunk is still a drunk. I find a modicum of comfort in the warmth and relaxation found by sipping a limited quantity of bourbon from time to time, this is not intoxication.
However, I also know people for whom even a single sip of bourbon seemingly inevitably brings about a cascade of events in their life that is harmful. They should not drink bourbon in any amount. I have a similar relationship with jelly beans. I seem unable to consume them in moderation, I will continue eating them until they are gone, no matter what quantity I have on hand, so I don't consume them at all. That seems like a silly example, but I used to be a rather severe diabetic, jelly beans were just as serious a situation for me as bourbon was for my friends who can't consume it in moderation. There are no absolutes here, really.
I don't offer my alcoholic friends a drink. I also don't lecture people endlessly about the wisdom of zen practice, or about how much I support a particular political persuasion. I used to do each of these things, I've made mistakes just as you have, but I seek to return to a state of being I enjoyed, and still can enjoy, before I grasp hold of the notion that alcohol is always okay, or zen practice is always wise, or that arch conservatives are always greedy hatemongers. There is a place one can exist before these notions arise, and one can return to that place at any time. This is also called Reality, some call it by other names, but it is always available to us at all time. It marks the Way,
So, a follower of the Way does not intoxicate oneself or others.