I posted this originally to the psychodelic thread... I wanted to give it its own place:

In neo platonic duelistic thought they divide knowledge into two groups,universal and particulars.

Particular knowledge is anything than can be expressed with logic or even sensed(sight,sound ,smell,etc,etc)
Universal knowledge on the other hand cannot be expressed thru logic or attained with the senses. It must come thru "revelation"

In the "beat-nic" era absract art was very popular. The reason was that some poeple believed that abstract art could communicate "universal" concepts. Thats what was meant when an art lover could "see" the picture. The viewer was somehow liberated from the limits of "particular" thought and could than grasp "universal" concepts.

Tripping on acid or mushrooms also eliminated the boundries established by "particular" thought. it placed you in a world that you could redefine using "universal" concepts.
Sythenesia is when you "hear" colours and "smell" sounds.