Dr Leary proposed that Marijuana helped unlock a lvl of consciousness allowing one to see in higher dimensional space. This seemed a little outlandish, but upon recent study, I've found that a better way to put it, is it helps one see more clearly through higher dimensional space.
What this means is, that one can see and understand reality more vividly for what it really is, possibility. It's almost as if when your sober, your drunk and you may simply not notice or care about much of what is going on to it's full extent, but when high you have more of an ability to indeed see through not just space more clearly, but higher dimensional space. But What is higher dimensional space? Well our universe only exists in 4 dimensions. You will never find another dimension that anything in our universe travels through on a macroscopic level. But there is in fact other dimensions that exist in our universe. They exist within the conscious mind of life, however subjective experience of conscious lifeforms is not documented in science or physics.
Marijuana stimulates your mind. This is a basic reason why such authorities such as your government disapproves it's use, over alcohol, which depresses your mind. They don't want you getting any ideas. The best way to handle a nation of people is to keep them dumb. You dont want them getting any ideas that might make them question their superior's authority. Because of this, all Dr Leary's efforts to understand the human mind and it's relationship with psychoactive's was slandered to be accepted by the world as little more than the insane ranting of a drug addict. With the coming of the new movement into the Spiritual Age perhaps we will see an age where we are finally able to accept the truth.