Earlier in the thread someone brought up the point that things that are pleasurable are biologically "good" and things that are painful are biologically "bad". However, the use of certain hallucinogins and hard narcotics would seem to contradict this, as they can cause immense pleasure but are also extremely harmful to the body and mind.
The pleasure centers can be fooled. Thats what drugs do. They are unnatural, in the sense that they bring no nutrients into the body. The reward mechanisms are primarily to do exactly that, to reward.
The effect of psychoactive drugs is actually supposed to be a preventative device in nature, like a poison, which discourages consumption by herbivores. This allows the plant to reproduce if its inedible in quantities. By coincidence, this "poison" happens to be attractive in smaller quantities and brings pleasure stimulus. If you were to eat enough to make a meal, you would be severely incapacitated, and likely not attempt it again. Nature knows nothing of using fire on it, or rendering the shit into needle form.
So the drugs actually do work as intended by nature. It is we who have circumvented the laws of nature and found ways to introduce the substances in pleasurable, smaller quantities.
By introducing pleasure with unnatural means, and gaining no nutritional value in the process, it becomes recreational. Recreational activities are supposed to be secondary, after maintaining health and the necessary living skills. If they rise in rank and become a primary activity, other things slip, like hygiene and social stability, mental alacrity, and the means of self-sufficiency like work, or its older reflection of hunting/gathering.
People will obviously rally around the argument of pot being natural and edible. And this is true. But if you ate a whole bowl full like a regular salad, you'd be sick as a fucking dog, flat on your back. Thats the benchmark, in a nutshell, and what proves its a recreational substance. You're supposed to be able to eat as much as you want and the pleasure is supposed to be an absence of hunger, craving of nutrition satisfied. Since you have to be careful about how much you ingest, and know it will have an intoxicating effect, it is to be recognized as a potentially harmful substance.
And believe me, I like pot, and most drugs. But my pro-arguments aren't so amateurish as the common fuckhead. Recreational use of intoxicants and psychedelics open some wonderful doors of perception, bring many positive introspective and creative things into the mind of the user, and society as a whole. They provide escapism from the mundane, and enjoyment if used properly. But only if they are kept in the proper #2 position, secondary and not primary, and used responsibly.
Of course, we'd probably have better luck with that if they weren't so taboo and treated by youth as a forbidden fruit, which promotes irresponsible use/abuse that paves the way to addiction in adults.