@Hoo, I will reply in a private message, in order not to meander too much in this thread. I'm unsure whether such a thing is appreciated. However, I would very much like to continue this talk. :-)

I think so far the conclusions that have been reached in this discussion can be summed up as that body and mind are caught up in a passionate love affair, which can sometimes have crippling and at other times luminous effects. Chemicals and mental states intermingle, giving rise to each other.

Addiction being one of the seemingly crippling effects that the love affair between body and soul can have, where there is longing or desire which needs to be fulfilled repeatedly yet is never fully fulfilled.

We have also spoken though of how there is a transformative effect in addiction or even mental illness in general, where overcoming a struggle is rewarded by becoming the subject of very pleasurable mind states. Overcoming the problem is a real struggle though (#thestruggleisreal), one must first go through a period of purifying oneself which can be painful.

Any further contributions are most welcome. :-)

I think that any idea can have positive and negative influences as distorted in the minds of people. The important thing I think is to look at both view points and place them in a context. Why do people feel this is a harmful philosophy, why do they feel it is a beneficial philosophy?

Without thought and language we would truly be like any other animal living on instinct. So the cogito ergo sum saying seems to imply at least that due to our capability to think we may call ourselves "human" and set ourselves apart from other species of animals.

However, descartes philosophy is interpreted also negatively in which case it is usually referred to as cartesian dualism. Dualism is the intuitive idea that there are always two sides of a coin so to speak: body and mind, day and night, white and black, etc. And I think no one would deny that contrast gives rise to perception. However, the "I" is always inclined to choose a side. Christ for example, when proclaiming what was good, in a way created the Anti Christ: that which is "bad" or "evil".

So thinking in strict dualities may be harmful, connecting these opposites and somehow creating a unity of complementary pairs out of them seems to be the solution.

Mind and body interact in immensely complex ways, we may not understand these mechanisms, but for sure these "realms" are not separate from each other. Without a body there would be no world to sense and there would be nothing to refer to. But without the mind nothing would be able to refer, there would be no "I" and experience would probably be an incoherent primordial soup, slightly laced by instinct.

Atop that, one must always take into account the difference between the actual words and the interpretation of the words.

@Hoo, I was talking to a friend the other day about ayahuasca and how, while I never did ayahuasca, I really did understand what it was about and what these people were after to experience. It's a sort of symbolic rebirthing process. In relation to the hero myth: the hero usually succumbs to hubris and is killed, or is deemed a "false prophet" and is killed. He visits hell, he has to watch himself in all fullness, there is no escape. He comes to self-realization in the fire. The hero usually returns after a descend into the earth. He is resurrected and reborn.
This all really shows parallels to mental illness, like depression. I was depressed and addicted so I had concocted this story to make me feel better, one where I would be reborn and could try again, but also, I believed in an essence making up me that would survive death. When I withdrew the projections a painful realization dawned that I had made up everything I believed in and I was in fact mortal, would die, would perhaps not return, maybe there was no god, etc. This was devastating.
I also got sick in the process, I started hallucinating and I was living in a complex world of thought that I had made up. When the visions started I felt exalted, but that soon changed. It was at times luminous, at other times utterly and completely terrifying. Always bizarrely psychedelic. I experienced my inner world as outer world and vice versa. Everything was entangled, it was very confusing (massa confusa).
I remember things vaguely up until the clinic. I was very afraid of something I had dubbed the Chaos Demon. And I thought I was going to die. So I finally let them admit me to a mental hospital. The first two weeks there are a black hole in my mind. I really feel as if my personality, or ego, or something, was disintegrating in the chaos. But something survived, a germ, a seed, it grew into what I now call me. It resembles the old me but is different in a lot of ways.
At first there was darkness. After that, just a flat, bland, nothingness. From that grew the first fireflies which would turn to lanterns that would lead me out of the darkness. It really was a process.
To return to the hero myth: I felt like I had fought a dragon. This psychedelic experience of four months was so intense I felt like a survivor. That was the key, after that it was always meditating on the visions, writing about them, explaining them to myself, trying to understand the madness.
Carl Jung has been a mentor through the whole process. Thanks to him I found so much meaning in the madness, it's insane. ;-) also, John Weir Perry has written interesting books on this subject.
After that I was fully enlightened to the fact of how much value there is in giving meaning, to my experiences and to the world.

Thank you all for your insightful replies. I'm sorry for my late reply. I wanted to take my time. I also had to help someone move unexpectedly last weekend and it has been over 30 degrees Celcius here in the Netherlands. I think it actually fried my brain a little.

@ArguingWAristotleTiff, thanks for your lovely words. I myself have no guilt attached to the addictions I have suffered from or am still caught up in. I have overcome my hard drug addiction, yet, I still smoke. I feel bad about it, sometimes I feel hopeless, but never guilty. I own up to the fact that these addictions are of my own choosing, perhaps even of my own making. So I can also "make them" go away.
I do not regret my party days, which really were about ten years of my life of doing hard drugs. It was excessive, it was crazy, and it may have led to insanity, but also to healing. I saw that there is a world apart from our everyday world, that there are states of mind except our everyday state of mind. That you can feel free and liberated when dancing and talking to strangers, how you feel no fear or sadness, there is just joy, or even ecstatic bliss.
All of this can make you see things in a different persective, like in the old mystery religions where initiates would dance and drink while being told the secrets of nature.
Then comes a time where you must face your addiction (to pleasure), and try to change. This is the hard part, I know... But when you overcome your dragon, you will feel like a victor.

@Bitter Crank, thank you for your replies, I am learning a lot. I naturally like the dog picture and I especially like what you say about the oxytocin being released at special or very lovely and meaningful moments in your life.

Why I am so interested in addiction and the nature/nurture debate (which we might as well call the nature + nurture discussion) is because it somehow is a good metaphor and starting point for thinking about mental illness in general.
Addiction can be seen as a battle we have to fight with ourselves, with our own mind. Just like any mental illness is really a battle for deliverance.
I once suffered from a psychosis that lasted for about four months. It was quite the trip. Of course no one knows exactly what a psychosis is, what causes it, what makes it go away or stay, etc.
The discovery of the release of chemicals in the brain may be a partial explanation for mental illnesses like acute schizophrenia, where one "suffers" from visions, hallucinations and "strange ideas". This idea has been around for at least a century. Though I think the search should be less focussed on serotonin and perhaps more on other psychedelic substances that exist in the body, like actual DMT.
The question remains what brings about these imbalances in the chemical make up of the body. The prevailing answer nowadays is: drugs and stress. I had done quite a lot of drugs in my day, so yea, that was held against me of course.
The other important point though is: no one really knows what the function of psychosis or mental illness is. We (as people) generally believe that madness, insanity, schizophrenia or psychosis, all of these related phenomena basically are meaningless nonsense that must be treated with pills because there is no time, money or expertise to ACTUALLY treat patients and make them better, so, the problem is subdued.
I am very inclined to think though that it actually has a function and is not meaningless sickness. It may be a portal to a genuine spiritual awakening (which of course is always a subjective experience).

@Hoo, thanks for the Hegel reference! I didn't know about that and will certainly check it out.

I am much interested in the topic of "opposites" being made into complements and I will try to explain why I think this is relevant here.
I came to the insight through reading the works of Carl Gustav Jung, some of you may know him. He was a doctor/psychologist/philosopher who died in the previous century. He talks about the "play of opposites" in his works, especially the ones related to alchemy. Alchemy is in a way the precursor of modern chemistry in the same way that astrology gave rise to astronomy. It sought a way to explain matter and to transform it.
Jung states that this "transformation" was sometimes a physical one (ie. trying to turn lead into gold) or a spiritual one (transforming the mind). He set up a hypothesis that the alchemical theory (almost fully shrouded in mystery) is basically a spiritual philosophy that has something to do with the phenomenon of projection.
Jung writes that the psyche has been "lost" or "imprisoned" in matter (we often project our internal microcosm or our ideas about the world onto the macrocosm, not seeing this is so) and the magnum opus or "work" would refer to becoming a master of one's own projections, withdrawing them (taking responsibility) and after that seeing things more clearly.
Now on to what this has to do with modern science. Albert Einstein has said that theoretical physicists (et al) are much inclined to think of their mental constructs not as such, but as actual reality. They do not discern between observer and the observed, so to speak. They think that what they have learned about reality is absolutely true, and their theory reflects reality perfectly.
They "project" their world view onto the world, and believe this is the world. Then they try to make this into an objective truth through the scientific method. However, all of this is man-made, even the scientific method and concepts like "truth" and "objectivity". We seem to be caught up in a world of projection, meaning: we realize not that there is a subject watching.
It is clear this applies to researchers who set up (design) an experiment and from this induce universal "truths". However, through this scientific method we may contemplate the concepts of subject and object thoroughly, and we may come to realize how and what we are projecting. So, through theoretical physics for example, one may come to self-realization, by almost meditatively examining theory.
I think this is the extent to which Carl Jung's theory can be extended. :-)

@Bitter Crank, thanks for your reply. I appreciate it! What I deduce from what you say is that genes affect the way in which we respond to our environment? Have I understood you well? You also say they "shape" our emotions, right? I may be nitpicking here, but I wonder how we (as humankind) have come to these conclusions. I am not at all saying I know better or something like that, I really don't know and I'm just always very curious how people have come to conclusions like that. I just want to learn. :-)

For example, I have to wonder: what are feelings and emotions? Are they the same or somehow different? I always thought of feeling as a personal inner experience and emotion as a sort of externalization of this feeling, a way by which we may communicate our feelings to others. If we take the two basic feelings, happiness and sadness... Are these phenomena "simply" chemicals having a mental effect? Does every psychological phenomenon have a biological counterpart or neural correlate or something like that? I somehow believe this must be true in a way, yet, is it possible for humans to know all of these mechanisms? And, does that mean that consciousness can in essence be reduced to chemistry? 

Like I said, I really don't know. All I know is that this either/or thinking, either biological or psychological, may be harmful or at least not productive. When it comes to the nature/nurture debate I think it is clear that it's not really a matter of the one or the other. We can't deny that we as humans have a body that is made up of all sorts of interacting materials (chemicals), we also can't deny that we have inner experiences of conscious awareness that we perceive as being somehow different from the "outer world" in a sense that they are personal.

Humans seem to think in dualities - biological/psychological, nature/nurture, inside world/outside world' etc. - while these dualities are always somehow connected or even intermingled; at least related. I myself am convinced that all dualities can also be viewed as pairs (of opposites) that somehow complement each other and form a unity. Though that is just a little alchemical theory, which may be totally irrelevant here.

Thanks everyone for your replies! As of yet I don't really know how to "mention" someone or even how to quote someone, but I'm sure I'll get the hang of it soon. (Edit: I found out how to mention people, so I edited my post.)

Opinions seem to differ. As was to be expected. :-)

@Unenlightened, thanks for the tip! It seems really interesting and I'll watch his Ted talk sometime.

@ArguingWAristotleTiff, is it perhaps that you somehow feel that if there is a biological component to addiction, one can feel less "guilty" of having been addicted? I think there is no shame in addiction either way, whether it be psychological or genes. I know how a little partying can, before you know it, turn into a full blown hard drug addiction. I know how something so "taboo" can become "normal" very soon. I know how there can be a paradoxical freedom in using: i felt temporarily free, though while actually I was imprisoned in an addiction.

@Barry Etheridge, I basically could have written what you write though I was merely trying to state my question a little more open ended. I fully agree with your statement that the research is basically mostly designed to prove the point. When not designed entirely to prove the point, one can still prove the point by interpreting the data to mean whatever one wants (to a certain extent). "Pure" science is not very easy to come by since experiments cost time and time = money. So yes, when a company wants some research done and they pay good money of course the scales will be in favor to them.

This is actually I think one of the bigger problems in modern day science, where a lot of theory poses as objective while that status of objectivity may perhaps be questioned. Also, I think the objectivity/subjectivity pair should be explored not just by philosophers but by all scientists who claim to produce truth.

I think this is very interesting! And such great answers, though some of them seem to prove Dennett's point. Philosophy tends to wander off into fantastic speculation or purely technical and theoretical abracadabra. I think what Dennett is saying is that when philosophy starts making claims about ultimate truth it gets a little pretentious. There seems to be only mystery. It is from a standpoint of not-knowing that in my opinion the best philosophies are written. It is from a standpoint of wanting to be right that philosophers become like children in a sandbox.

I really wonder why anyone would care to prove if either the universe is finite or infinite. It is beyond our capabilities to prove such a statement either way. I firmly do not believe in the big bang theory, yet, it is clearly questionable to want to prove the universe is infinite. We simply can't know for sure unless we observe its infinity. Which would take an infinity. Claims about what exists outside of this universe (which is all there ever was, is and will be) I think are also meaningless, just like determining the age of this universe, or claiming any absolute truth concerning the universe expanding or contracting or being stationary. The real question I think is why do people ask these sort of questions? What is the purpose of saying either this or that when all that is possible is mere speculation about human observations? Why do we insist on trying to "prove" matters that are completely beyond our capabilities to prove or refute (only perhaps theoretically)?