Chrysippus
Chrysippus of Soli was a Greek Stoic philosopher. He was a native of Soli, Cilicia, but moved to Athens as a young man, where he became a pupil of the Stoic philosopher Cleanthes. When Cleanthes died, around 230 BC, Chrysippus became the third head of the Stoic school. A prolific writer, Chrysippus expanded the fundamental doctrines of Cleanthes' mentor Zeno of Citium, the founder and first head of the school, which earned him the title of the Second Founder of Stoicism.
Chrysippus excelled in logic, the theory of knowledge, ethics, and physics. He created an original system of propositional logic in order to better understand the workings of the universe and role of humanity within it. He adhered to a fatalistic view of fate, but nevertheless sought a role for personal agency in thought and action. Ethics, he thought, depended on understanding the nature of the universe, and he taught a therapy of extirpating the unruly passions which depress and crush the soul. He initiated the success of Stoicism as one of the most influential philosophical movements for centuries in the Greek and Roman world. The linguistic orientation of Chrysippus' work made it difficult for its students even within the Stoic school.
Of his several written works, none have survived except as fragments. Segments of some of his works were discovered among the Herculaneum papyri.
Life
Presumably of Phoenician descent, Chrysippus was the son of Apollonius of Tarsus, and he was born at Soli, Cilicia. He was slight in stature, and is reputed to have trained as a long-distance runner. While still young, he lost his substantial inherited property when it was confiscated to the king's treasury. Chrysippus moved to Athens, where he became the disciple of Cleanthes, who was then the head of the Stoic school. He is believed to have attended the courses of Arcesilaus and his successor Lacydes, in the Platonic Academy.Chrysippus threw himself eagerly into the study of the Stoic system. His reputation for learning among his contemporaries was considerable. He was noted for intellectual audacity and self-confidence and his reliance on his own ability was shown, among other things, in the request he is supposed to have made to Cleanthes: "Give me the principles, and I will find the proofs myself." He succeeded Cleanthes as head of the Stoic school when Cleanthes died, in around 230 BC.
Chrysippus was a prolific writer. He is said to rarely have gone without writing 500 lines a day and he composed more than 705 works. His desire to be comprehensive meant that he would take both sides of an argument and his opponents accused him of filling his books with the quotations of others. He was considered diffuse and obscure in his utterances and careless in his style, but his abilities were highly regarded, and he came to be seen as a preeminent authority for the school.
He died during the 143rd Olympiad at the age of 73. Diogenes Laërtius gives two different accounts of his death. In the first account, Chrysippus was seized with dizziness having drunk undiluted wine at a feast, and died soon after. In the second account, he was watching a donkey eat some figs and cried out: "Now give the donkey a drink of pure wine to wash down the figs", whereupon he died in a fit of laughter. His nephew Aristocreon erected a statue in his honour in the Kerameikos. Chrysippus was succeeded as head of the Stoic school by his pupil Zeno of Tarsus.
Of his written works, none survived except as fragments quoted in the works of later authors like Cicero, Seneca, Galen, Plutarch, and others. In 2004, segments from Logical Questions and On Providence were discovered among the Herculaneum papyri. A third work by Chrysippus may also be among them.
Study
Chrysippus had a long and successful career of resisting the attacks of the Academy and hoped not simply to defend Stoicism against the assaults of the past, but also against all possible attack in the future. He took the doctrines of Zeno and Cleanthes and crystallized them into what became the definitive system of Stoicism. He elaborated the physical doctrines of the Stoics and their theory of knowledge and he created much of their formal logic. In short, Chrysippus made the Stoic system what it was. It was said that "without Chrysippus, there would have been no Stoa".Logic
Chrysippus wrote much on the subject of logic and created a system of propositional logic. Aristotle's term logic had been concerned with the interrelations of terms such as "Socrates" or "man". Stoic logic, on the other hand, was concerned with the interrelations of propositions such as "it is day". Though the earlier Megarian dialecticians – Diodorus Cronus and Philo – had worked in this field and the pupils of Aristotle – Theophrastus and Eudemus – had investigated hypothetical syllogisms, it was Chrysippus who developed these principles into a coherent system of propositional logic.Propositions
Chrysippus defined a proposition as "that which is capable of being denied or affirmed as it is in itself" and gave examples of propositions such as "it is day" and "Dion is walking." He distinguished between simple and non-simple propositions, which in modern terminology are known as atomic and molecular propositions. A simple proposition is an elementary statement such as "it is day." Simple propositions are linked together to form non-simple propositions by the use of logical connectives. Chrysippus enumerated five kinds of molecular propositions according to the connective used:Thus several types of molecular propositions, familiar to modern logic, were listed by Chrysippus, including the conjunction, the disjunction, and the conditional, and Chrysippus studied their criteria of truth closely.
Conditional propositions
The first logicians to debate conditional statements were Diodorus Cronus and his pupil Philo. Writing five-hundred years later, Sextus Empiricus refers to a debate between Diodorus and Philo. Philo regarded all conditionals as true except those which with a correct antecedent had an incorrect consequent, and this meant a proposition such as "if it is day, then I am talking," is true unless it is day and I fall silent. But Diodorus argued that a true conditional is one in which the antecedent clause could never lead to an untrue conclusionthus, because the proposition "if it is day, then I am talking" can be false, it is invalid. However, paradoxical propositions were still possible such as "if atomic elements of things do not exist, atomic elements exists." Chrysippus adopted a much stricter view regarding conditional propositions, which made such paradoxes impossible: to him, a conditional is true if denial of the consequent is logically incompatible with the antecedent. This corresponds to the modern-day strict conditional.Syllogistic
Chrysippus developed a syllogistic or system of deduction in which he made use of five types of basic arguments or argument forms called indemonstrable syllogisms, which played the role of axioms, and four inference rules, called themata by means of which complex syllogisms could be reduced to these axioms. The forms of the five indemonstrables were:Of the four inference rules, only two survived. One, the so-called first thema, was a rule of antilogism. The other, the third thema, was a cut rule by which chain syllogisms could be reduced to simple syllogisms. The purpose of Stoic syllogistic was not merely to create a formal system. It was also understood as the study of the operations of reason, the divine reason which governs the universe, of which human beings are a part. The goal was to find valid rules of inference and forms of proof to help people find their way in life.
According to Sextus Empiricus, Chrysippus held that dogs use disjunctive syllogism, such as when using scent to pick which path to run down. This was in contrast to a tradition since Aristotle, who saw reasoning as man's defining aspect.
Other logical work
Chrysippus analyzed speech and the handling of names and terms. He also devoted much effort in refuting fallacies and paradoxes. According to Diogenes Laërtius, Chrysippus wrote twelve works in 23 books on the liar paradox; seven works in 17 books on amphiboly; and another nine works in 26 books on other conundrums. In all, 28 works or 66 books were given over to puzzles or paradoxes.Chrysippus is the first Stoic for whom the third of the four Stoic categories, i.e. the category somehow disposed is attested. In the surviving evidence, Chrysippus frequently makes use of the categories of substance and quality, but makes little use of the other two Stoic categories. It is not clear whether the categories had any special significance for Chrysippus, and a clear doctrine of categories may be the work of later Stoics.
Later reception
Chrysippus came to be renowned as one of the foremost logicians of ancient Greece. When Clement of Alexandria wanted to mention one who was master among logicians, as Homer was master among poets, it was Chrysippus, not Aristotle, he chose. Diogenes Laërtius wrote: "If the gods use dialectic, they would use none other than that of Chrysippus." The logical work by Chrysippus came to be neglected and forgotten. Aristotle's logic prevailed, partly because it was seen as more practical, and partly because it was taken up by the Neoplatonists. As recently as the 19th century, Stoic logic was treated with contempt, a barren formulaic system, which was merely clothing the logic of Aristotle with new terminology. It was not until the 20th century, with the advances in logic, and the modern propositional calculus, that it became clear that Stoic logic constituted a significant achievement.Epistemology
For the Stoics, truth is distinguished from error by the sage who possesses right reason. Chrysippus's theory of knowledge was empirical. The senses transmit messages from the external world, and their reports are controlled not by referring them to innate ideas, but by comparing them to previous reports stored in the mind. Zeno had defined impressions of sense as "an impression in the soul" and this was interpreted literally by Cleanthes, who compared the impression on the soul to the impression made by a seal on wax. Chrysippus preferred to regard it as an alteration or change in the soul; that is, the soul receives a modification from every external object that acts upon it, just as the air receives countless strokes when many people are speaking at once.In the receipt of an impression, the soul is purely passive and the impression reveals not only its own existence, but that also of its causejust as light displays itself and the elements that are in it. The power to name the object resides in the understanding. First must come the impression, and the understandinghaving the power of utteranceexpresses in speech the affection it receives from the object. True presentations are distinguished from those that are false by the use of memory, classification and comparison. If the sense organ and the mind are healthyand provided that an external object can be really seen or heardthe presentation, due to its clearness and distinctness, has the power to extort the assent that always lies in our power, to give or to withhold. In a context in which people are understood to be rational beings, reason is developed out of these notions.