Many years ago I enquired of Ouspensky whether it would be a good thing for me to follow his example and to experiment with hashish, with a view to observing the alteration it brought about in my consciousness. His reply was brief and to the point:
"Only if you have any doubts about the existence of higher levels of consciousness. A drug permits of our looking, as it were, over the garden wall and discovering what lies out there in the psychological landscape beyond it. If you are already convinced of the existence of higher levels of consciousness then there is no point in making experiments with drugs to prove it."
I was convinced, even then, of their existence and have found it quite unnecessary to take pills for the purpose of proving it.
Dr. Kenneth Walker - The Mystic Mind p.137