Athens shone forth as the source of philosophical light for the Mediterranean world even while the classical polis waned as the forum of political and social freedom. The increasing internationalization of ideas and ideals disseminated Greek models widely but also challenged Athenian philosophy. What is the relation between the universal laws of Nature and existing social structures? Should one's life be rooted in tradition or logic? To what should one be loyal, one's place of birth or present residence? Are physics, the study of Nature, and ethics, the practice of proper conduct, two aspects of one architectonic science? The Stoic movement was an initiator of and a response to the new tides of creative thought and the interaction of ideas. Zeno was born in Citium, a Graeco-Phoenician city on Cyprus, about 336 B.C., the year Alexander became king of Macedonia. When Zeno came to Athens, Xenocrates and Polemon of the Academy, Theophrastus of the Lyceum and Stilpo at Megara had all failed to sustain the intense ethical concern permeating Plato's dialogues. Disappointed by the lacklustre leadership in Athenian philosophical activity, Zeno established a school around 300 B.C. in the Stoa Poikile, the painted porch which housed the frescoes of Polygnotus. According to tradition, he was concerned about dilutions of the philosophy of Epicurus which might lead to relativistic hedonism and a flat denial of any sense of the sacred. He called for a reaffirmation of the classical virtues, appreciating the practical spirit of the Cynics, the example of Socrates and the metaphysics of Heraclitus. Though considered a severe man, he was honoured in Athens during life and after death, and left a remarkable disciple to carry on the spirit of his work – Cleanthes.
Cleanthes of Assos in the Troad was born about 331 B.C. and was originally a boxer. He arrived in Athens with only four drachmae in his possession. Working by night as a water-carrier for a professional gardener, which earned him the nickname Phraeantles, he used his days to attend the lectures of Crates the Cynic and, eventually, Zeno. Perhaps as a consequence of his early athletic interests, Cleanthes was well known for his industriousness. He learned slowly, but the lessons he mastered were deeply impressed upon his memory. He listened carefully to Zeno's powerful if unsystematic lectures, and studied Zeno's life with the greatest attention. Watching Zeno during his hours of retirement and in personal contexts, Cleanthes concluded that Zeno lived the philosophy he espoused and was truly a worthy teacher and guide. Taking one step at a time in argument and in life, his slow manner earned him the popular title of the Ass, but his enduring patience with all whom he met illustrated a fundamental feature of the Stoic standpoint. When Zeno died in 263 B.C., Cleanthes became the acknowledged head of the Stoic school.
A great generosity of spirit suffused the teachings of Cleanthes. Though under pressure to dispute the principles of other schools, he chose to respect the strong points in the perspectives of others and offered alternatives only when he was convinced that they were inadequate. Chrysippus became his disciple and successor, and the reverence he showed his master long after the latter's death indicates the quality of character and profundity of teaching of Cleanthes. Antigonus, king of Macedonia, also became his pupil and was the only individual from whom Cleanthes accepted a donation. He preferred to support himself by his own hands even after he assumed the chair of the Stoic school. Following Zeno's lifelong intuition that events in nature are indices for appropriate human conduct, Cleanthes chose his moment of death. A serious ulcer forced him to undertake a fast for a time, but when the danger had passed, he refused to resume eating on the grounds that since he was already halfway along the road to death, he saw no reason to retrace his steps. He died in 232 B.C., having lived almost a century.
Though revered by his disciple and successor, Chrysippus, ancient opinion tended to slight Cleanthes as unoriginal and phlegmatic. Like Speucippus, Plato's successor in the Academy, Cleanthes exemplified loyalty to the teachings of his master, preferring to elaborate their meaning and implications rather than lay claim to new doctrines of his own making. His gentleness of manner and willingness to appreciate the perspectives of his opponents contrasted sharply with Zeno's fiery and occasionally harsh nature, perhaps to the disappointment of some who longed for heated debates. Cleanthes carefully expounded the Stoic view in areas untouched by Zeno in an effort to exhibit its completeness and consistency. Concepts originally employed exclusively in physics or ethics were shown to apply in both. He wrote some fifty books outlining his ideas and applying them to the way one should live one's life so that the harmonies which maintain order in the cosmos could be seen to be relevant to human conduct. While Chrysippus turned his attention to the logic and criteria of argumentation, Cleanthes chose to express himself in the rich language of the Greek epics. He invoked the gods and the divine science in poetry, believing that the largest number of people would hear and be moved by discourses in this medium. Unfortunately, only a few of his poems survive virtually intact, though his teachings are partially preserved by later authors.
Zeno had argued that Deity is the creative fire in the universe, the source of its evolution and coherence. The Stoics identified God with the primordial fire of Heraclitus, the highest aether, Anima Mundi and providence. Cleanthes brought to this formal requirement of Stoic thought an ardent devotion which exalts the creative fire as the focus, foundation and director of the cosmos, and the Logos as the source of order and harmony within it. For Cleanthes, there is a distinct contrast between Deity and matter, between the Logos and the cosmos, but this duality is understood within an embracing unity. He called the Heraclitean fire phlox, 'flame', to suggest a broader meaning, and identified it with the all-pervading aether, the plenum of space. Sometimes he likened it to the sun and to the principle of heat. Eventually he adopted the term pneuma, 'spirit', as best combining the ideas of creative fire and the Logos. Pneuma was conceived as a substance analogous to air but associated with the powers of warmth and elasticity. It is immanent in the universe as God and in the human body as the soul. The metaphysical isomorphism of the human being and the cosmos implies a correlative dynamics in which ethics mirrors metaphysics. As with Plotinus and Porphyry, this application of a sense of the sacred to the structure of the cosmos sanctifies any science of the stars, requiring a rejection of mechanical astrology and mechanistic astronomy. Curiously, while the identification of pneuma with the sun gives the radiant orb a central place in Stoic metaphysics, Cleanthes was suspicious of the Pythagorean teaching that the sun is the physical centre of the solar system, held by Hicetas of Syracuse and Ecphantus as well as Aristarchus of Samos and others. Cleanthes wondered if Aristarchus should be tried for impiety, perhaps because a physical heliocentric system ignores the fact that the earth is the centre and focus of solar and planetary influences that affect the nature of rational activity. Theories which attempt to account for phenomenal observations of the heavens alone fail to explain the relation between macrocosm and microcosm, and thus ignore that aspect of Deity called Providence. For Cleanthes the stars were foci of the creative force of the aether, condensations of the universal medium of space.
Given the unity of soul and cosmos, human faculties can be derived from cosmic processes. For the soul to understand any idea or perception it must be essentially like the object. In this sense there is no unbridgeable dualism between mind and matter. The mind is impressed by objects through sensation and organizes its thoughts through a combination of sensation and reasoning. While life makes "entries on the mind" from birth onwards, as if the mind were a tabula rasa waiting to be inscribed, the soul is not passive, for it actively cooperates in efforts to gain impressions upon which reason can work. Method is therefore important in daily living and in education. A careful study of syllogisms and fallacies will provide some basis for correct understanding, but even though it is an aid in the formulation of teachings, it cannot guarantee true premises. Precise definition wedded to acute observation will help. Amidst ridicule for the practice, by redefining common terms and coining new ones, Cleanthes brought a clarity to Stoic doctrines that set the example for his successors and won admiration even from critics.
Cleanthes insisted that there is a logic to fate, heimarmene, which does not allow possibilities to be rendered impossible. Fate guides and conditions the range of events and actions, and so all that happens providentially is also decreed by fate, but not all that is the result of fate occurs providentially. Evil exists in the world because it follows from lines of possible action, but evil may not be blamed on Deity, any more than the fact that the human being can err is to be blamed on the essential nature of soul. Without the creative fire, the universe itself could not unfold, but since whatever comes into existence must perish, a universal conflagration must eventually dissolve all that exists, after which will remain Deity alone. All souls exist until that time, but must perish in their individuality when every conceivable contrast is merged into the eternal unity; but since souls are essentially deific, their destiny thereafter must remain a mystery beyond temporal experience and conceptualization.
Since fate cannot render the possible impossible, it remains open for human beings to alter circumstances. The creative power of Spirit acts from within without through centres of tension and intent, tonos, which is, ultimately, the Logos. Each human soul, the Logos of the cosmos which is the body and its powers, is a tonos. By altering the ratios of tension, the dynamics of intention, one alters one's destiny. By applying the concept of tonos found in Heraclitean physics to the realm of ethics, Cleanthes could show that good and evil are not in the action or its consequences, but rather in the will. Cleanthes warned, "He who abstains from some disgraceful action, yet all the while has desire for it, will some day do it when he gets the opportunity." The cultivation of the virtues realigns the ratios of the tonos in human beings. Cleanthes assumed that every human being has some intuitive awareness of the moral good:
While one might readily assent to this broad proposition, one may miss its deep implications. Engendering the good from within will be advantageous, but if the other qualities are to be considered seriously, virtue cannot be utilitarian. Only the whole can be taken into account from the standpoint of the Logos, for any lesser perspective will fail to fit the principles of conduct to the laws of Nature. One should aim to lead one's life calmly and sensibly, but not in terms of conventional wisdom.
Any attempt to plunge headlong into some radically altered form of life will only distort tonos in a different direction. Virtue is one, and so a human being's life is inherently consistent, can be made consciously consistent with chosen principles that reflect the cosmic order, and can be improved by everyone. In a world which honoured many distinctions, Cleanthes wrote a book to show that women were the equal of men in the capacity and ability to become wise, for "Virtue is the same in men and women."
The two great obstacles to developing ethical wisdom are pleasure and inexperience. The desire for pleasure can disfigure the reasoning process and discolour perception. Though pleasure may be as natural as pain or any other sensation, Cleanthes could not recommend it, for he thought that pleasure is of no value, whereas pain awakened one to the need for adjustment to cosmic harmony. Pain is difficult to endure only because of inexperience and expectations of pleasure. He did not suggest that one should seek pain; rather one should see work as a discipline which nurtures virtues. Once the individual had set himself the task of gaining wisdom, he would discover that there are no distinctions of soul. All humanity belongs to one vast cosmopolis which is both an ideal and a fact in nature where there can be no distinction of class or race, Greek or barbarian, no Aristotelian doctrine of nations fit to rule and nations fit only to be enslaved, no gradations of human beings. The cosmopolis is the country of one's true citizenship. It is maintained neither by coercion nor statecraft. Good will is the cohesive power, for "Love is God" and the essential root of security.
Cleanthes, and Zeno before him, refused the honour of Athenian citizenship so as not to appear disrespectful of their places of birth and to emphasize that they were citizens of the universe. The constitution of the cosmopolis is based upon the laws of Nature, the Logoic harmony radiating from the creative fire which is Deity. The cosmopolis is realizable in daily consciousness because there have been, are and always will be wise men who already dwell in the cosmopolis even while roaming the earth. No Stoic teacher claimed to be such a being, and some flatly denied it, but all pointed to them as the exemplars of the possibility and end of the whole human community – a cosmopolis of wise men, the closest reflection on earth of the absorption of souls into Deity. The divine nature of soul enables an individual to go against the course of nature, but the innermost essence of soul will require unwilling cooperation even of evil-doers. Rather than fight the inevitable movement of the Logos, one can gain the freedom of joyous participation in the invocation of the good which is ethical action sanctified by a purified understanding of nature.
Cleanthes crystallized his teachings in one poetic summary which reflects his own fervent devotion to the ideal he had come to recognize as real and patiently worked to share with the whole of humanity.