As much as I respect Dr. Venkman and his work, I mean no disrespect to Ghostbusters by saying that Peter Venkman is an idiot! I want to know how a man like that can get a doctorate, and what could his dissertation have been about?

I think I heard somewhere that the guys had to help Peter out, big time! To get his PHD.

A number of friends of mine who have gotten doctorates have summed up university education thus;

Bachelor degree teaches you the basics.
Masters degree teaches you to teach others the basics.
Doctorate work teaches you the beauracracy of the places where you teach others the basics.

I can see Pete cheating off of Ray and Egon through their bachelor degrees.
He was probably the most popular teachers assistant while working on his masters (again, with help from Ray and Egon on his thesis).
And if anybody knows how to work a system, it's Pete. It didn't last forever (what with them getting kicked out of the university), but it was fun while it lasted.