In one respect, Baptists can claim to be pioneers. They were the first to claim full religious liberty, a conception to which their fellow-Separatists had not yet attained. John Smyth held that the magistrate must confine himself to civil transgressions, and must not meddle with religion at all. Thomas Helwys printed in 1612 the first assertion of this doctrine in English, frankly telling the king of England that he had no authority over a man’s religion, which lay between a man and his God; even heretics, Jews or Turks, were not to be persecuted.
Roger Williams carried this principle of religious liberty to America, where it was carried into practice in Rhode Island, and finally was incorporated in the constitution of the United States. In this important and now accepted principle, Baptists have led the way for their fellow-Protestants, and it is not surprising that a passion for liberty was and is a chief characteristic of the Baptists. They fought for it in Cromwell’s army, in which they took a much more prominent place than has usually been recognized. They suffered severe persecution for it through the period of the Restoration. They continued to exist through the common religious lethargy of the earlier eighteenth century into the new life of its later decades, as legally ‘tolerated’ religious groups. They helped to secure, in the nineteenth century, the removal of most of the remaining disabilities.
Today, their sympathies with those who still suffer under such disabilities are quickly aroused. No one can live reflectively amongst Baptists without being conscious of this passion for liberty as a leading characteristic of their type of faith (most familiarly represented in the late John Clifford). It goes back to their Separatism and the training of the local Churches in self-government and vigorous individualism.
–Robinson, H. Wheeler. “Present Day Faiths: The Faith of the Baptists.” The Expository Times. 1927: 451-455.