This episode traces how a small, controversial Protestant movement from early modern Poland — the Socinians or Polish Brethren — helped shape arguments about reason, Scripture, and religious toleration that circulated in seventeenth‑century England and beyond. We follow the movement’s writings and networks, the ideas they promoted about God, Christ, and human conscience, and the routes by which those ideas entered a conversation that would include John Locke. Expect close attention to key Socinian texts (the Racovian Catechism, Fausto Sozzini’s writings) and to the political, confessional, and intellectual pressures that made their voice both dangerous and influential.