2.4.3.1 Logic and the theory of knowledge The goal of Stoic...

2.4.3.1 Logic and the theory of knowledge The goal of Stoic philosophy is to find a rational basis for ethics: they start with logic, the science of thoughts and discourses. Stoic logic included grammar, and thus Stoics are founders of the traditional science of grammarthe dialectical part of logic deals with the theory of knowledge: of which there are two problems: [^1] what is the origin [source] of knowledge, and [^2]what is the criterion of knowledge.

Sources: Knowledge is gained through perception. The mind has the faculty of forming general ideas and concepts of a large number of cases which are alike and of forming universal judgments. This faculty, reason, is a faculty of thought and speech identical with the universal reason which pervades the worldthe Stoics posited objected rationality in the world and yet opposed the Platonic doctrine of ideas: only particular objects have real existence and universals are subjective abstractions.

Criterion: A sense image is true when it is an exact copy of the object. A concept is true when it agrees with the qualities pervading similar things. How shall we distinguish true from false? Man is entitled to his conviction when he has satisfied himself that his sense organ is in normal condition, that the percept is clear and distinct and that repeated observations by him and others verify his first impression.

Since true premises are deduced logically from true premises, the faculty of drawing correct inferences is accordingly another means of reaching the truth and dialectic an essential qualification of the Stoic sage. Consequently, the stoics gave considerable attention to formal logic, particularly the syllogism, which they regarded as its most important phase [they made minor additions to Aristotle's scheme of syllogism and revised his table of categories]. Previous…