Extract from a letter from C. G. Jung to Victor White, on the subject of psychedelics. June 1954.

Is the LSD drug you’re referring to mescaline? It has indeed very curious effects, of which I know far too little. I don’t know either what it’s psychotherapeutic value with neurotic or psychotic patients is. I only know there is no point in wishing to know more of the collective unconscious than one gets through dreams and intuition. The more you know of it, the greater and heavier becomes your moral burden, because the unconscious contents transform themselves into your individual tasks and duties as soon as they become conscious. Do you want to increase loneliness and misunderstanding? Do you want to find more and more complications and increasing responsibilities? You get enough of it.

If I once could say that I had done everything I know I had to do, then perhaps I should realise a legitimate need to take mescaline. If I should take it now I would not be at all sure that I had not taken it out of idle curiosity. I should hate the thought that I had touched on the sphere where the paint is made that colours the world, where the light is created that makes shine the splendour of the dawn, the lines and shapes of all form, the sound that fills the orbit, the thought that illuminates the darkness of the void.

There are some impoverished creatures perhaps, for whom mescaline would be a heaven sent gift without a counter poison, but I am profoundly mistrustful of the pure “gifts of the gods”, you pay very dearly for them.

This is not the point at all, to know of or about the unconscious, nor does the story end here. On the contrary, it is how and where you begin the real quest. If you are too unconscious, it is a great relief to know a bit of the collective unconscious. But it soon becomes dangerous to know more, because one does not learn at the same time how to balance it through a conscious equivalent. That is the mistake Aldous Huxley makes, he does not know that he is in the role of Zauberlehrling, sorcerer’s apprentice, who learned from his master how to call the ghosts, but did not know how to get rid of them again.