  Reinach mentions many social acts in his treatise on “The A Priori Foundations of the Civil Law” (1913)—commanding, requesting, warning, questioning and answering, informing, enacting, revoking, transferring, granting, and waiving of claims—but he devotes the most attention to the act of promising. Drawing on the theory of essences or intrinsically intelligible structures referred to above, Reinach offers the following examples of a priori truths about what he sees as the intrinsically intelligible structure instantiated through the performance of a promising act: