Within my lifetime there has been a significant shift in the cultural perspective on marijuana usage. Just today, as I sat in Starbucks sipping my decaf coffee (I didn't want to abuse the drug caffeine), I was simultaneously reading a forum discussion between Pastor's on the subject of whether or not Christians should smoke weed and eavesdropping on a conversation between people next to me who were discussing their perspectives. Both parties at the table next to me discussed the rampant drug use in the high school that they were familiar with; one of them said, "Marijuana has replaced alcohol as the drug of choice. It's so much safer! It's all natural, too." The other (apparently after the other person had left, because I wasn't watching them and there was no response), gave the traditional perspective: "It's so dangerous...it's a gateway drug."
The shift in cultural perspective means that in some parts of the country, recreational marijuana use is legal, and in all likelihood the rest of the nation will follow this trend. Many Christians have refrained from using marijuana simply because it has been illegal; as that will no longer be the case, they are actually forced to have a perspective on it and think through why a Christian should abstain or not abstain. If you live in one of those areas where it is already legal, there's a good chance the discussion has already come up: should a Christian smoke marijuana?
Let me say up front that I am not talking about medical usage of marijuana. Marijuana is proven to relieve the symptoms of some ailments, and the research has increasingly demonstrated potential value in cases such as epilepsy. A friend-of-a-friend uses it for just this purpose, and claims that it's the only thing that works to keep him from the seizures that he's had since he was born. My assumption is that he's telling the truth, and that if it works, more power to him. But that's a post for a different day. In this case, I'm talking about recreational use specifically.
The first place the Christian looks to see if there is any instruction or guidance on the subject is the Bible. So long as marijuana was illegal, the discussion on whether or not a Christian should partake was really just a question of whether or not a Christian was obligated to follow the laws of the land. Since the Bible makes clear that they should, the Christian response to marijunana was similarly black and white. If it is legalized, then that argument becomes moot. And since marijuana usage is not specifically addressed in the Scripture, we have to turn to related issues to determine whether or not it's use is acceptable. Those two related issues are the Bible's teaching on alcohol usage, and the teaching on sobriety generally.
Alcohol & Sobriety
Although there are differing perspectives within the Christian community on whether or not a Christian should ever drink alcohol, it is an issue that should fit solidly into the "conviction" category of beliefs. A conviction is a belief that a Christian has that is addressed by Scripture, but not in a way that makes the conclusion obvious. As a result, our convictions–although informed by Scripture–are often heavily influenced by our personal experience, and thus we can come to different conclusions and still remain friends without attempting to dismantling the other person's faith.
The Bible does address alcohol usage, but does so in a way that leaves open the option for Christians to drink. Those in favor of having the occasional drink point out that Jesus first miracle was turning water into wine; those opposed to drinking alcohol point out that the main point of the miracle had to do with purification, not wine drinking, and in any case because Jesus allows something doesn't mean he condones it. In his letters, Paul would encourage the early Christians to "remain sober-minded"; this is the teaching that seems to be behind Paul's exhortation not to get "drunk like the pagans, which leads to debauchery". If there is a clearly-expressed biblical principle related to alcohol, this is it. The Christian should maintain his wits about him; he or she shouldn't voluntarily submit their mental focus to anything that would negatively impact their sobriety.
The reason for this, I think, has less to do with the results of being under the influence, and more to do with the opportunity cost of the loss of sobriety. The results are certainly important, as Paul points out: getting wasted often leads us to make very unwise choices, sometimes to the point that we don't remember we made them. Those effects are temporal, however. They are for this life only. The greater tragedy is the opportunity cost of the loss of sobriety; that is, when we are not sober-minded, we will be ill-equipped to share the Gospel if an opportunity arises. This gets to the heart of Peter's exhortation to the believers in his first letter: always be prepared to give an answer for the hope that you have. There is much that this could mean, but it certainly includes the understanding that the Christian person should be always ready to share the Gospel, and anything that would inhibit our ability to do that should be put aside. Thus, the desirable state of mind for the believer is the one in which he or she is sober and ready to make a defense of the Christian faith.
So then, we are left with these two principles: first, that the usage of alcohol itself is never condemned, and second, that what is condemned is anything that would cause us to lose our wits. If we take the first principle to mean that alcohol usage is allowed, then certainly the guiding principle should be the second: there are limits to God's good creation! The Psalmist remarks that wine gladdens our hearts (Psalm 104), but the wise teacher of the proverbs reminds us that it can also lead us astray; to follow it would be unwise. (Proverbs 20)
These are the two principles that I would apply to the recreational usage of marijuana. Will it cause you to lose your wits? Can you occasionally smoke marijuana and still be in a state of mind to share the Gospel? If so, then I cannot see a biblical reason that it would be disallowed. This is not to say that it would be wise to smoke marijuana. That is a different question and one that I have very little interest in answering at this juncture. Everyone makes unwise choices, and often with regularity. What I'm interested in is what God thinks about it. And as far as I can tell based on what he has chosen to reveal, the best we can do is develop a personal conviction on the issue. We can decide for ourselves based on the Scripture and encourage others to see things how we see them, but we're not allowed to chastise someone for choosing differently than us, if they at least understand what the Bible teaches. If God wanted to be clear, he certainly could have been. But he wasn't. And that means that as we apply what he has told us, we might not all agree. That's what makes it a conviction, rather than an essential.
And at the end of the day, we can still all get along.