Propositions have been used to explain cognitive thought, language, communication, and philosophical concepts of truth, necessity and possibility. Based on the theories of Frege and Russell, propositions are structured abstract objects, independent of mind and language, possessing essential and intrinsic truth-conditions. Recent theorizing doubts the existence of propositions and our ability to grasp, entertain, and know them, but most importantly, whether the abstract approach can explain propositions. The papers in this volume use these doubts to explore new critical and constructive directions. This book was originally published as a special issue of the Canadian Journal of Philosophy.