95. Alone amongst the hearers of Zeno Dionysius of Heraclea abandoned his principles, and went over from the camp of virtue to that of pleasure. A painful disease of the eyes had made him abandon the doctrine that ‘pain is no evil[46].’ His secession was used by Antiochus as an argument against the doctrine of comprehension or certain knowledge[47]. That his life after he became a Cyrenaic was openly scandalous[48] we need not too readily believe: such accusations may easily be mere deductions from his supposed philosophic principles. Dionysius appears to have been a particular friend and admirer of the poet Aratus[49].
Of the less important hearers of Zeno we have the names of, amongst others, Athenodorus of Soli[50], Callippus of Corinth[50], Posidonius of Alexandria[50], and Zeno of Sidon[50]. The last, if he existed, must be kept distinct from other Zenos, such as Zeno of Tarsus the pupil of Chrysippus, and Zeno of Sidon the Epicurean philosopher.
Cleanthes.
96. We come last amongst Zeno’s hearers to Cleanthes of Assos in Asia Minor (331-232 B.C.), who succeeded Zeno as head of the school when already advanced in years, and presided over it for a whole generation. In personal character he was a worthy successor of Socrates, Diogenes, and Zeno. He was trained in hardship and willing endurance[51]; and if he did not quickly understand, yet all he learnt was deeply impressed upon him[52]. He studied Zeno’s life even more attentively than his doctrines; lived with him, watched his hours of retirement, inquired whether his actions corresponded to his teaching[53]. Himself a man of the people, he ardently desired to spread his convictions amongst the many, and chose verse as the best means to express clearly his meaning and win access to men’s ears[54]. He remained constant to Zeno’s teaching[55], but he inspired it with a fresh enthusiasm and developed it in more consistent detail. He is before all things the theologian of Stoicism. The belief in the deity, which in the fragments of Zeno’s teaching appears merely formal and argumentative, becomes in the verse of Cleanthes ardent and dominating. God is the creator and the director of the world; his Logos gives it order and harmony. In God’s designs it is the privilege and duty of man to cooperate; but since he is possessed of free will, it is also within his power to make a futile opposition. In this way the good and the bad stand in definite contrast. Finally, right knowledge and right action are only possible by association with the deity through praise and prayer.
His poetry.
97. It is our good fortune to possess several complete poems of Cleanthes, which are of more value to us towards appreciating his standpoint than a hundred detached sentences would be. The hymn to Zeus[56] is the most important, and its likeness to the opening of Aratus’ Phaenomena[57] will not escape notice.
Hymn to Zeus.
Supreme of gods, by titles manifold
Invoked, o thou who over all dost hold
Eternal dominance, Nature’s author, Zeus,