A study of the Protestant utopian movement that began in Germany, inspired in large measure by the writings of Johann Valentin Adreae, and came to England through the efforts of the émigré Samuel Hartlib.The first chapters examine Andreaes utopian writings, including the Rosicrucian manifestos, as part of his lifelong commitment to found a Societas Christiana, a spiritual élite that would improve religious and intellectual life. His writings sparked a transnational movement in early modern Europe. The most significant of the German learned societies are discussed: The Societas Ereunetica, Unio Christiana, and Antilia. The latter chapters consider Hartlibs English circles and various utopian and learned societies in the 1650s.This study contributes to our understanding of the role that secret" societies and epistolary networks had in the republic of letters."