ACL2 Version 2.7 - A programming language in which you can model computer systems and a tool to help prove properties of those models. Available under GPL and runs on various platforms. Includes related download links. LWB - Logics Workbench. MUltseq - A generic sequent prover for propositional finitely-valued logics. MUltlog - Takes as input the specification of a finitely-valued first-order logic and produces a sequent calculus, a natural deduction system, and clause formation rules for this logic. Isabelle - A generic theorem proving environment developed at Cambridge University (Larry Paulson) and TU Munich (Tobias Nipkow). Includes logic, documentation and free download. ProofPower - A suite of tools supporting specification and proof in Higher Order Logic (HOL) and in Z notation. LOOM - A language and environment for constructing intelligent applications. It is a research project in the Artificial Intelligence research group at the University of Southern California's Information Sciences Institute. The goal of the project is to develop and field advanced tools for knowledge representation and reasoning in Artificial Intelligence. PVS - The PVS Specification and Verification System. Available for Sparc machines with Solaris 2 and Intel x86 Machines with Linux compatible with Redhat 5 or later. Required is Emacs (version 19 or later), recommended LaTeX and Tcl/Tk. Download by FTP. Tree Proof Generator - An implementation of the semantic tableaux method for classical propositional and predicate logic, written in JavaScript/DOM. Gateway to Logic - A collection of web-based logic programs offering a number of logical functions: interactively or automatically build proofs, check theorems, and operate on propositional logic formulae. llprover - A linear logic prover that searches a cut-free proof for the given two-sided sequent of first-order linear logic. DC Proof Online - New proof-writing software to teach the fundamentals of logic and proof. Enables users/students to write error-free proofs by selecting rules of inference, axioms, etc. from convenient drop-down menus. Includes tutorial and exercises. Proof General - Comprehensive Gnu-Emacs and XEmacs interface for several theorem provers including Coq, Isabelle, Lego, and Phox. Church - Program understands the different types of lambda expressions, can extract lists of variables (both free and bound) and subterms, and can simplify complicated expressions. Uses Python. WinKE - An interactive proof assistant based on analytic tableaux, and designed for the teaching of deductive reasoning. Ordering information is available at this site, as are academic papers on the design of the software. Bertrand - Bertrand solves sets of first-order predicate logic statements for satisfiability (consistency), validity, and equivalence. It also checks single statements for "logical truth" (tautology) and "logical falsity" (self-contradiction). Subject-identity is supported. User can "step through" the solution algorithm as Bertrand solves a problem, and/or check the graphic tree produced. j'Imp Theorem Prover - An automatic theorem prover based on set of support and ordered resolution for first-order logic. j'Imp is part of the Orbital library. This library is a Java class providing object-oriented representations and algorithms for logic, mathematics, and artificial intelligence.