Reality And Hallucinogens

To be honest I came of age in the late 60s and early 70s and I have smoked a lot of cannabis taken LSD more than once and mescaline even more.  I never had a bad trip and always found it to be an enjoyable experience.  What it did do was make me question "reality" - that is, what is it?
Via Andrew Sullivan we have this interesting post by Miles Klee, Blowing Your Mind.

Aldous Huxley in 1954 wrote as eloquently as one can about taking mescaline, which accomplishes more or less what Psilocybe semilanceata does. He had a more pleasant day than young Edward’s family, however, and in The Doors of Perception quoted Cambridge philosopher Dr. C. D. Broad in describing the mental processes modified:

Each person is at each moment capable of remembering all that has ever happened to him and of perceiving everything that is happening everywhere in the universe. The function of the brain and nervous system is to protect us from being overwhelmed and confused by this mass of largely useless and irrelevant knowledge, by shutting out most of what we should otherwise perceive or remember at any moment, and leaving only that very small and special selection which is likely to be practically useful. 

“According to such a theory,” Huxley continues, “each one of us is potentially a Mind at Large. But in so far as we are animals, our business is at all costs to survive. To make biological survival possible, Mind at Large has to be funneled through the reducing valve of the brain and nervous system.

In other word Hallucinogens don't alter reality they simply give us an overdose of reality.  The drugs disable the filter that determines what we perceive.  This pretty well matches my experiences.  It's been 40 years since I have performed any chemical experiments on my mind but I'm am convinced that it has impacted the way my mind works - the way I see things and in a positive way.  I question what I perceive which I think is a healthy thing.  Are drugs dangerous?  Of course they are but I have not personally known anyone who had a "bad trip."   I have known many who's lives were ruined by alcohol however.