How did Gottfried Wilhelm Leibniz contribute to symbolic logic?

Gottfried Wilhelm Leibniz made pioneering contributions to symbolic logic in the 1680s, creating a system remarkably similar to the later work of George Boole. His primary logical goals included:12

• Lingua Characteristica Universalis: A "universally characteristic language" designed to represent concepts notationally and iconically, making them easily understood regardless of native language.12
• Calculus Ratiocinator: A "calculus of reason" that used symbols and established rules to perform logical deductions mechanically or algorithmically, similar to arithmetic.12

Leibniz developed an "intensional" logic where symbols represented properties or concepts rather than individual things. He defined the truth of a judgment as the predicate concept being "included in" the subject concept, utilizing algebraic notation to represent syllogisms as sequences of equations.12

Despite his brilliance, Leibniz published little on these specific systems during his lifetime, leaving his work largely without influence on the subsequent development of logic until the 20th century. His vision of using machines to verify inferences, however, anticipated modern computer science.12