Can we reach enlightentment with recreational drugs?

Being respectfull on everyones answers and to the question, i think that this question in particular doesn't need any references from buddhism knowledge. The answer would be no simply, because enlightment is not an experience you could replicate or that, the brain it self experiences, as, lets say lucid dreams or abnormal perceptions. Enlightment is the fully transformation of the mind and the brain you could say too. Enlightment is a path, it means a life of dedication. Psychoactive drugs, are just a pleasure ride in comparison. Good question nevertheless.

Disclaimer: This is not a Buddhist perspective this is just what I think about the matter.

I've had my fair share of experiences with various mind-altering substances. When I first had those experiences they challenged many assumptions that I had about pretty much everything. Those experiences allowed me to see how fallible this mind is. They also allowed me to see just how dependent my experience was on the neurochemical activity of the body. That was a long time ago. I was not practicing Buddhism back then. These days I derive no benefit whatsoever from drugs and I see them as a hindrance to the path. It's just another thing that belongs to the world and is bound up with suffering. If you're really curious about something and decide to take something please do as much research as possible and take all the necessary precautions before you do. But no drug is going to make you enlightened, I guarantee you that much.

Can we learn to ride a snowboard with recreational drugs?

Enlightenment is not something you "see". It is more like a skill. Like riding a snowboard, you can't quite put it into words, but you once you have acquired it, you know how it works. Like with snowboarding, there is a bunch of little elements that go into it: you know how gravity works with different types of terrain, you have a good feel for different snow conditions, you have intimate familiarity with the edges of your board etc. A drug may make you temporarily more sensitive to some of these, and less sensitive to others, but it won't make you a good rider, only practice will.

Enlightenment is a skill in the area of experiencing reality, shaping reality, and interacting with reality. A drug may show you some interesting sides of reality. But it won't make you a good shaper and surfer of reality. Only practice will. And the practice involves learning to control your perception, starting with basic reactions, like getting frustrated or obsessed, all the way to your perception of your own identity. By working with your emotions and thoughts, both in day to day life and in meditation, you become intimately familiar with "the edge of your board". You get my metaphor.

Drugs may be useful for someone stuck in a bad loop - to help them realize that reality is an interpretation we make. But that's about all they can do. If you are not too stupid you can achieve the same result by crossing your eyes. The rest of the path requires effort, lots and lots of it.

The Maha-satipatthana Sutta says that this is the on and only way for enlightenment hence recreational drugs will not help in this aspect.

Also another Sutta which give guarantee of Enlightenment, if practiced in the right way, is the Anapanasati Sutta.

The above meditation are generally called Vipassana. When practiced you will get the Knowledge of What is the Path and Not the Path with other Insight Knowledge. Then it is when you will know for sure. But until then you could take the description in the scriptures at face value, that chemicals may really give you enlightenment, and path to enlightenment is the Noble 8 Fold Path and the practice Vipassana until you find out for yourself by verification through your pratice.

My answer is based on the teachings I got from Vajrayana teachers.

It is useful to use a metaphor of a mirror or a screen. Our mind is a perfect mirror and all our experiences are the reflections on that mirror. In our everyday life we habitually focus on and identify with those reflections - when something nice is appearing, we are happy, when something disturbing pops up - we are sad. With the help of Buddhism we want to understand the mirror itself - our perfect mind that is aware and able to experience everything. Enlightened Buddha is not disturbed by negativity around him because he has a full understanding of the nature of things around him - everything is empty in its essence and has nothing to do with good or bad. He is also not disturbed when something beautiful disappears - impermanence is all-pervading, whatever has a beginning will eventually has an end as well. The only lasting thing is the perfect, indestructible mind.

So now let's look at drugs. They indeed can change our perception and allow us to experience extraordinary states of mind. But do they help us to recognize the mirror? Not really, they only change the reflections on the mirror. We don't like our grey everyday life so we take some drugs to add some colours to the movies reflected on our mirror. As soon as the drugs stop working, the colours bleach out and we suffer because we get attached to those more vibrant images and handling grey everyday reality becomes harder. So in a way drugs can make us attached to fascinating experiences which, sadly, are not permanent.

Think of a movie theatre - there is a modern screen and advanced sound system. Spectators can enjoy watching various movies and if they pay extra (drugs taking), the advanced technology is turned on so they can have breathtaking experiences while watching the latest 3D HD sci-fi movies. But the screen is also capable of screening dramas, thrillers and really violent and disturbing images. Spectators have their likes and dislikes so they will be demanding only nice and fascinating movies, but sometimes they would buy a ticket and will be disappointed that the movie they've just seen wasn't as great as they expected. Buddhism invites you to become the owner of the cinema - to learn how the screen works and understand that the pictures are just reflections on your awesome screen and the technologies you have in your theatre are fantastic. You won't be bothered by the type of the movie or the ugly/annoying actors. Rather, you would say - wow, this theatre is capable of this, how fascinating!

Well I feel that it is extremely naive to think that taking recreational drugs can help the mind build empathy. It is almost the same as saying that watching p**nography helps build empathy towards women. I know what I say may sound controversial, but I will explain this from a medical perspective. In reality, consuming recreational drugs such as marijuana, cocaine etc. has almost the same medical effects as engaging in sexual activities, over consuming food, watching p**nography, consuming large quantities of alcohol or engaging in any other activity deemed by Buddhism as "Activities that disrupts focus, attention and concentration; while garnering unwholesome feelings such as distraction, lack of focus, attention deficit, impatience and anger, while over-accumulating uncontrolled negative energy within our mind and body (sexual/filled with greed)".

This is explained by taking into account the medical effects of the afforementioned "addictive activities". All these activites succeed in doing almost the same thing within the brain matter: that is, elevating/creating imbalance in the chemicals in our bain. When we see a meal/person/situation that generates greed in our mind, it is actually something that causes release of DOPAMINE in our brains. Different activites have different levels of Dopamine releasing effects; with MORPHINE administration (as a painkiller in certain patients) , viewing p**nography, consuming drugs that creates addiction having the highest degrees of dopamine release. Dopamine imbalance is caused by repeatedly engaging in such aforementioned activites, that leads the person into an Addictive Cycle, that is both viscous and extremelt difficult to overcome. This is quote on quote "viciously addictive" purely by the fact that all these activites done in immoderation causes what is reffered to as "tolerance" in our brains. That is, we need to consume/engage in ever increasing amounts of afforementioned activites, to create the same level of dopamine release in our brains, that ultimately results in our brain to experience the same level of satiety as before.

We are in reality, hijacking our brain's natural rewarding pathway. The pathway that normally cause us to "feel rewarded by engaging in a wholesome activity" is replaced by the "perception of feeling rewarded" purely by consuming a substance- that does not require hardwork, commitment and focus. Hence as an animal filled with greed, the mind would crave the easy route.

Hence in conclusion, such activities are unwholesome and creates lack of focus, which is the ultimate enemy for any meditator. Our level of focus is primarily our weapon in progressing our practice of meditation further than it was before. While engaging in such activities, the brain only percieves the feelings of empathy, happiness, fulfilment; and they aren't necessarily "true feelings". I say this because, for a feeling to be "true", it should not be codependant on consuming an unnatural substance. For example, empathy that arises from consuming drugs is not true empathy that we can garner say by practicing Metta meditation or by helping another human being, since the latter actually creates the feelings of happiness and compassion without co-dependance on consuming any other substance. Hence, it is extremely dangerous to be the victim of such dangerous habits that eventually breaks down our mind's eye of what might necessarily be "right" and "wrong".

From the perspective of the 5th precept then the answer would be no. The fifth precepts states

I undertake the training rule to abstain from fermented drink that causes heedlessness

But I've often seen this rendered as

I undertake the training rule to abstain from intoxicating substances

While the fact that it breaks the precept might leave you unconvinced these precepts are viewed as training principles i.e. it is the best way to achieve liberation or enlightenment. So in many traditions intoxicants are not seen as an aide to liberation.

Also the point of the Buddhist path is to see things as they really are. It's difficult to see how one might see things as they really are when one's mental processes are been influenced by recreational drugs of any sort. Reality is difficult enough as it is without dulling, altering or confusing the six senses (I'm including mind here as one of the senses).

The founder of the the sangha that I practice with, Sangharakshita, has taken psychedelic drugs on a couple of occasions to see if there are commonalities with the Buddhist path. From his perspective there wasn't though I believe he found the experience interesting. I have to say this was a controversial action by an often controversial figure. I have never heard any recommendations from him to try this approach so this would be another reason that I would personally discount recreational drug use as an insight practice.

As an aside, the beatnik guru Alan Watts (another contraversial figure) had a more sympathetic attitude to this approach. The most famous quote (which I will include with a little context) is

Psychedelic experience is only a glimpse of genuine mystical insight, but a glimpse which can be matured and deepened by the various ways of meditation in which drugs are no longer necessary or useful. If you get the message, hang up the phone. For psychedelic drugs are simply instruments, like microscopes, telescopes, and telephones. The biologist does not sit with eye permanently glued to the microscope, he goes away and works on what he has seen

So even Alan Watts wasn't a whole-hearted proponent of this approach. He saw them as a tool at best and in no way replacing meditation or other traditional insight methods. Just to be clear though - Alan Watts wasn't a traditional Buddhist if he was one at all so this comment though interesting has probably limited relevance to this site. Please see it as a footnote to this answer.