Book excerpt: William Penn played a crucial role in the articulation of religious liberty as a philosophical and political value during the second half of the seventeenth century and as a core element of the classical liberal tradition in general. This volume illuminates the origins and development of Penn's thought by presenting, for the first time, complete and annotated texts of all his important political works. His thought has relevance not only for scholars of English political and religious history, but also for those who are interested in the foundations of American religious liberty, political development, and colonial history. His social status, indefatigable energy for publication, and command of biblical and historical sources give Penn's political writings a twofold significance: as a window on toleration and liberty of conscience, perhaps the most vexing issue of Restoration politics; and as part of a broader current of thought that would influence political thought and practice in the colonies as well as in the mother country.