Once u'll learn QFT,u'll know that before diagrams (not one,there are in infinite number for each field theory),u have to knwo the rules.Feynman rules that is.Fortunately,they are in finite number.Once u'll know the rules,u can build virtually an infinite number of diagrams.
My guess is:pathintegrals+diagramatics=pure Richard P.Feynman genius.
Daniel.
