The Ancient and Middle Stoics share with the Presocratics the ill fortune of having their work lost. There is, however, an enourmous amount of fragments and reports that have come down to us from contemporary or later philosophers and writers with an interest in philosophy (such as Alexander of Aphrodisias, Cicero, Galen, Plotinus, Plutarch, Proclus and Sextus Empiricus), theologians (for example, Clement and Philo of Alexandria, Eusebius and Origen), and doxographers (Diogenes Laertius and Stobaeus). Some of these sources are hostile and, therefore, they tend to distort the original doctrine. But they all provide us a great amount of evidence for the knowledge of Stoicism. This book offers a large selection of this evidence (Greek and Latin texts with critical apparatus and philological notes accompanying a Spanish translation and philosophical commentary). Some significant passages from Seneca, Musonius Rufus, Epictetus and Marcus Aurelius are also included.