It would be an understatement to say that McKenna was one of the most unique visionary minds of the late 20th century. He passed away in 2000, but thanks to the Internet, his brilliant madness lives on.
Some of his ideas are still waaaaay out there, but he was loquacious and witty in a way that was completely genius & novel.
Whether or not his various individual theories were correct, he introduced a concept that I think should be further examined- the fractal modeling of time.
I think fractal models can greatly increase our understanding of both space and time, in the same way the development of calculus has advanced science greatly since Newton's day.
Despite McKenna's tendency to externalize his wacked-out experiences onto the Universe-at-large, both physical and temporal experience are ultimately only in our heads.
Here are a couple select nuggets of Terence's crazy wisdom that I've seen posted recently:
Terence McKenna: Art
Terence McKenna: Life is a Joke