Sapienti os in corde, stulto cor in ore esse – Johann Gottlieb Heineccius on natural duties concerning free thought and free speech

In his "Elementa Iuris Naturae et Gentium" Johann Gottlieb Heineccius presents a unique account of love as the principle of natural law, referring to the main concern of early modern protestant theories of natural law: the importance of securing subjective rights by a law. Heineccius accepts the universal character of subjective rights derived from human nature, claiming their protection as natural duties required by a law. This chapter provides an attempt to explain the specific ways in which Heineccius deals with the paradoxical situation that the protection of subjective rights by a natural law theory requires certain limitations of the use of such rights, in order to avoid the mutual collision of such rights. For this purpose it focuses on the rights to free thought and free speech, which are very good example for that. While the first part reconstructs the way in which Heineccius claims the specific concern of natural law and points out continuities and discontinuities with his predecessors, the second part focuses on the requirement of natural law for limitation of free thought and free speech in case of collision of subjective rights