"While every history of ancient Judaism and Christianity gives a detailed picture of the Pharisees, none systematically and critically analyzes the traits and tendencies of the discrete sources combined to form such an account. Consequently, we have many theories but few facts, sophisticated theologies but uncritical, naive histories of Pharisaism which yield heated arguments unillumined by disciplined, reasoned understanding. Progress in the study of the growth of Pharisaic Judaism before 70 A.D. will depend upon the accumulation of detailed knowledge and a determined effort to cease theorizing about the age. We must honestly attempt to understand not only what was going on in the first century, but also - and most crucially - how and whether we know anything at all about what was going on.
"Here you are invited to share the painful task of assessing difficult sources and criticizing the nature of extant information about the Pharisees before 70 A.D.. At the outset, you may learn more than you wanted to know about the Pharisees, but the real reward of your labor ought to be mature skepticism about the nature of historical knowledge."
from the Preface