These are the proceedings of the Workshop on Quantum Logic held in Erice (Sicily), December 2 - 9, 1979, at the Ettore Hajorana Centre for Scientific Culture. Quantum logic, which has now a history of some forty or more years, has seen remarkable growth during the sixties and seventies.

1: Classification of Different Areas of Quantum Logic, and Open Problems.- Classification of different areas of work afferent to quantum logic.- Assumptions and interpretations of quantum logic.- 2: Comparison and Unification of Different Approaches to Quantum Theories; Problems of Interpretation.- What are quantum logics and what ought they to be?.- Charting the labyrinth of quantum logics: a progress report.- Realism and quantum logic.- What does quantum logic explain?.- A new approach to equivalence in quantum logic.- How to rewrite a stochastic dynamical theory so as to generate a measurement paradox.- The quantum logical and the operational description for physical systems.- 3: Formal Quantum Logic; Axiomatics.- Partial referential matrices for quantum logics.- Some metalogical pathologies of quantum logic.- Quantum logic as an extension of classical logic.- Sequential quantum logic.- Entailment and Quantum Logic.- Some problems and methods in formal quantum logic.- 4: Modal Interpretations of Quantum Logic.- A modal interpretation of quantum mechanics.- The dialogic approach to modalities in the language of quantum physics.- The inner language of operational quantum mechanics.- 5: Quantum Set Theory.- Quantum set theory.- Quantum sets, assemblies and plexi.- Omologic as a Hilbert type calculus.- Measure and integration in quantum set theory.- 6: Advances Concerning Mathematical Structure; Other Problems.- Commutativity and generalized transition probability in quantum logic.- Representations of Baer *-semigroups and quantum logics in Hilbert space.- A non-standard quantum logic with a strong set of states.- Description of compound physical systems and logical interaction of physical systems.- Products of logics.- Space time structure from quantum logic.- Causal logic of Minkowski space-time.- Propositional systems in field theories and lattice-valued quantum logics.- Non-linear integration and signed measures on von Neumann algebras.- On the inter-relations of the three quantal principles.- On the non-unique decomposability of quantum mixtures.- Motion and form.- Participants.- Author Index.