According to Leibniz, natural language, despite its powerful resources for communication, often makes reasoning obscure since it is an imperfect mirror of intelligible thoughts. As a result, it is often difficult to reason with the apparatus of natural language, “since it is full of innumerable equivocations” (On the Universal Science: Characteristic (undated); G VII, 205/S 18). Perhaps this is because of his view that the terms of natural language stand for complex, or derivative, concepts—conc