Logical Foundations of Computer Science : International Symposium LFCS 2020 Deerfield Beach FL USA January 4 7 2020 Proceedings This book constitutes the refereed proceedings of the International Symposium on Logical Foundations of Computer Science LFCS 2020 held in Deerfield Beach FL USA in January 2020. The 17 revised full papers were carefully reviewed and selected from 30 submissions. The scope of the Symposium is broad and includes constructive mathematics and type theory; homotopy type theory; logic automata and automatic structures; computability and randomness; logical foundations of programming; logical aspects of computational complexity; parameterized complexity; logic programming and constraints; automated deduction and interactive theorem proving; logical methods in protocol and program verification; logical methods in program specification and extraction; domain theory logics; logical foundations of database theory; equational logic and term rewriting; lambda and combinatory calculi; categorical logic and topological semantics; linear logic; epistemic and temporal logics; intelligent and multiple agent system logics; logics of proof and justification; non monotonic reasoning; logic in game theory and social software; logic of hybrid systems; distributed system logics; mathematical fuzzy logic; system design logics; other logics in computer science. Computability of Algebraic and Definable Closure Observable Models Countermodel Construction via Optimal Hypersequent Calculi for Non Normal Modal Logics Completeness Theorems for First Order Logic Analysed in Constructive Type Theory On the Constructive Truth and Falsity in Peano Arithmetic Belief Expansion in Subset Models Finitism Concrete Programs and Primitive Recursion Knowledge of Uncertain Worlds: Programming with Logical Constraints A Globally Sound Analytic Calculus for Henkin Quantifiers Feedback Hyperjump Syntactic Cut Elimination for Intuitionistic Fuzzy Logic via Linear Nested Sequents On Deriving Nested Calculi for Intuitionistic Logics from Semantic Systems Parameterised Complexity of Abduction in Schaefers Framework Tracking Computability of GPAC Generable Functions Modal Type Theory Based on the Intuitionistic Modal Logic Lifting Recursive Counterexamples to Higher Order Arithmetic On the Tender Line Separating Generalizations and Boundary Case Exceptions for the Second Incompleteness Theorem under Semantic Tableaux Deduction.