Baptists, like other Christians, are defined by doctrine—some of it common to all orthodox and evangelical groups and a portion of it distinctive to Baptists. Through the years, different Baptist groups have issued confessions of faith—without considering them to be creeds—to express their particular doctrinal distinctions in comparison to other Christians as well as in comparison to other Baptists. Most Baptists are evangelical in doctrine, but Baptist beliefs can vary due to the congregational governance system that gives autonomy to individual local Baptist churches. Historically, Baptists have played a key role in encouraging religious freedom and separation of church and state.