The Leibniz System is a software package for the development and implementation of logic-based intelligent systems. The package covers various aspect of the construction of such systems with modules for: - logic computation - learning logic formulas from data - discretization of data - subgroup discovery from data - data estimation by a lazy learner - dimension reduction of models - decomposition of graphs and matrices - solution of constrained optimization problems involving single or multiple objective functions. All programs are written in C using the ANSI standard. Installation is intended under Linux/Unix. Installation using other operating systems should not be difficult but is not covered in the manual.