But how are we to reconcile with this view the Stoic teaching of a plurality of virtues and their mutual relations? As the common root from which they spring, Zeno, following Aristotle, regarded understanding, Cleanthes, strength of mind, Aristo, at one time health, at another the knowledge of good and evil. [631] Later teachers, after the time of Chrysippus, thought that it consisted in knowledge or wisdom, understanding by wisdom absolute knowledge, the knowing all things, human and divine. [632] From this common root, a multiplicity of virtues was supposed to proceed, which, after Plato’s example, are grouped round four principal virtues [633]—intelligence, bravery, justice, self-control. [634] Intelligence consists in knowing what is good and bad, and what is neither the one nor the other, the indifferent; [635] bravery, in knowing what to choose, what to avoid, and what neither to choose nor to avoid; or, substituting the corresponding personal attitude for knowledge, bravery is fearless obedience to the law of reason, both in boldness and endurance. [636] Self-control consists in knowing what to choose, and what to eschew, and what neither to choose nor eschew; [637] justice, in knowing how to give to everyone what is his due. [638] In a corresponding manner, the principal faults are traced back to the conception of ignorance. [639] Probably all these definitions belong to Chrysippus. [640] Other definitions are attributed to his predecessors, [641] some more nearly, others more remotely, agreeing with him in their conception of virtue. Within these limits, a great number of individual virtues were distinguished, their differences and precise shades of meaning being worked out with all the pedantry which characterised Chrysippus. [642] The definitions of a portion of them have been preserved by Diogenes and Stobæus. [643] In a similar way, too, the Stoics carried their classification of errors into the minutest details. [644] [(c) Mutual relation of the several virtues.]