Protagoras of Abdera, Gorgias of Leontini (437 b.C.), Hippias and Prodicus

While Protagoras was older, these three were active, when Socrates drank the hemlock in 339 B.C.

Protagoras of Abdera (500 - 435 B.C.)

Protagoras was supposed to be born around 481 B.C. in Abdera in Thracia (where possibly Leucippus and Democritus were also a native), while Taylor and Burnett considered his birth in 500 B.C. Protagoras seemed to come to Athens around 450 B.C. Pericles enjoyed his talent and association. Indeed Protagoras was the greatest sophist of all.
By Pericles' request, Protagoras was supposed to draft the constitution of Thurioi, the new colony founded around 444 B.C. As one of the important guests, Protagoras was in Athens at the outbreak of the Peloponessian War in 431 B.C. and during the famous plague of 430 B.C.
Diogenes Laërtius mentions the story that Protagoras was indicted for blasphemy because of his book on the gods, but he was escaped from Athens before the trial and drowned on the crossing to Sicily as well as his books were burned at the marketplace in Athens. This should take place at least prior to the oligarchic revolt of the Four Hundred in 411 B.C. Both Taylor and Burnett based their dating of Protagoras on Plato's Protagoras, in which Protagoras was portrayed as an elderly human-being, at least 65 years of age around 435 B.C. Since Plato mentioned that Protagoras died at the height of his activities (acmé), we tentatively set the date of Protagoras 500435 B.C.
The most celebrated word by Protagoras was,

Human-being is the measure of all things, of those that are that they are, of those that are not that they are not.

In two respects this statement of relativism in epistemology and ethics allows us two different interpretations respectively, namely if "human-being" strictly signifies 1) the individual, or 2) the group of people such as a given society at a given period.
One of the sources of this quotation was Plato's Theaetetus . In this context, Plato interprets "human-being" as referring to the individual, so Protagoras turned out to be advocating a subjectivistic relativism, when he talked about one individual's sensation may radically differ from others'.
On the other hand, "things" (ta krémata) could a) mean simply the objects of experience, or b) encompass such things as values.
In the historical context, however, it is of cardinal importance to comprehend what kind of role the meaning of this quatation played and what influence this clause exercised on his contemporary and on his followers.
Protagoras' thesis, "Human being is the measure of all things...," thus, provided the philosophical foundation for the sophistic interpretation of "wisdom." Supported by this thesis of Protagoras, the sophists freely advocated subjectivistic individualism concerning not only sense perception, but also truth in general. They further agured that values including morality be not objective, but purely subjective like the matter of taste.
In order that information is to be knowledge, it must be not only true to a given individual, but true universally regardless of a particular society or of a given period. Knoweldge in this sense was flatly denied by Protagoras and his followers.
They also denied that there is no universal morality or ethical duties at all. Any morality, any system of ethics is a product of the given society and thus is relative to it.
If indeed knowledge is relative to a given individual at all, the wisdom, a system of knowledge, must be non-existent at all and must become non-sense.
Thus this wisdom, to Protagoras and the rest of sophists, turned out to be no other than the skill or art by which one can persuade the majority. This art was called the eloquentia.
This phenomenon of Protagoras and his teaching in relativism did not come out of the blue, but there must be a certain social need at the time in the Athenian culture. What was demanded of Protagoras by those wealthy Athenians?
The need which Protagoras keenly sensed was to educate the youth of the wealthy Athenian aristocrats to be an influential, powerful, competent political leader, following the ideal of image of Pericles who ruled Athens for thirty years.
However, as mentioned above, what was considered to be a better or more excellent human-being, construed by Protagoras and his followers, was de facto no other than a better orator, a more eloquent arguer or persuader, for it was the most important means in democracy to sway and obtain the support of and take the control of the masses. The political power was considered in the democratic Athens to be literally consisting in the art of persuasion, hé rhétoriké, eloquentia or oratoria.
What was in demand for success in Athens at that time by the majority of the political élite who were well to do and were conscious of the strong need of education of their youth was well fulfilled by the offer of sophists, how one-sided it may appear from the eye of Socrates and Plato.
It was the skill of demagogy.
In the efficient skill for political success, many of the leading Athenians saw an ideal of being a better human-being. Against this demand to and fullfilment by sophists, it was Socrates who was ready to fight for the sake of genuine humanistic education, i.e, the education of the youth as a good human being as a whole. It was Socrates' contention that not such "wisdom" as the rhetoric, but the pursuit of wisdom (= philosophy in the sense of love of wisdom) is the essential means to educate the human-beings to be better and morally excellent, that preceeds to money, political success, reputation. That moral excellence and virtue was what ultimately makes the human being happy.
Although it was quite questionable whether those sophists genuinely were interested in re- establishing and teaching morality, sometimes the sophists' teaching, as it followed Homer's footsteps, had nevertheless an aspect of moral eduction, as Werner Jaeger suggested. An example may be found in Prodicus' teaching (arguments) on Heracles, who, as a mythological hero, underwent twelve hardships. when Heracles, the son of Zeus, was deliberating on how to lived his life, there appeared two women, the one who was beautiful and sexually attractive offered Heracles the future life of earthy happiness without any hardship, whereas the other woman told Heracles that the genuine good life can never be attained by such an easy way, but gods set out many a hardship before the true happiness and the good life. Heracles took the hard way of life. The story of the same had been told long before in the epic form that the agon (strife) was necessary to attain the good and superior life. This traditional moral teaching was presented by Prodicus in the form of arguments, which was quite new.
As Werner Jaeger suggested, the theme was the continuation of development of Homer and Hesiod's educational task, but whether it fulfilled its task is questionable.
This limitation of education to the rhetoric revealed many faults and defects. There existed no philosophical School called Sophistic, but what bounded them together was their common professional activities, that was aimed at fulfilling the demand and need of the time.
Once again, although the ideal of education conceived by Protagoras was great, in reality what he taught was supposed to be mere rhetoric, and Gorgias, too, is said to have said that rhetoric was sufficient to education human-being to be a better human-being.
For, by this means and skill, one can not only protect oneself, but also can govern and control others. It appeared probably very simple and easy for the people to learn and people was excited about acquiring such a skill. In actuality the education by the sophist lead itself to an easy going, convenient direction, namely that the rhetoric could and should be able to handle easily all the difficulties and hardships!
For example, Gorgias was to have said that his argument for Heléné should be a joke. The art of persuasion must be capable of arguing both the pro- and the con-side to the issue (dissoi logoi, cf. at the end of the section Sophists). Therefore, for the sophists, it did not matter whether or not one pursues truth.
In contrast, Socrates and his followers (Plato, Aristotle and other philosophers (=lovers of wisdom)) stood by the very truth itself and by cultivating one's moral virtues.
The same hold true among Socrates and his followers in regard to the rewards for fees. While the sophists taught only those who could afford to pay them, Socrates and his followers taught not for the monetary reward, but for the sake of the pursuit of wisdom itself, for the intrinsic value of philosophy.
While the sophists claimed that they possessed wisdom (the art of persuasion), Socrates is said to have said that he only knew that he possessed no wisdom of goodness or beauty. This Socrates called a sort of wisdom only allowed to the finite humans in Plato's Apology of Socrates.
Xenophon, the great Athenian historian, said:

The sophist resembled to a prostitute, for he taught only in return of money and without love (just as a prostitute sleeps with the customer solely for money without love), but the genuine education must be pursued with love of the educated, there must be love in the foundation of education!

Prodicus of Ceos

Prodicus came from the island of Ceos in the Aegean Sea. Prodicus was Socrates' contemporary, although he could be a little younger than Socrates.
Plato in general talked about him with an irony, but he did positively speak of Prodicus in his DialogueTheaetetus.
Socrates (= Plato) in Theaetetus told that he sent to Prodicus a man who had not been pregnant with wisdom while this young lad was in Socrates' company. Through his association with Prodicus, the young man became no longer "barren."
In the a pseudo-Platonic Dialogue Axiochus he, the following thought was advocated:

Death is desirable because it helps us to escape from the evils of life.

This thinking may be very close to Prodicus'. For, according to Prodicus:

Fear of death is irrational, since death concerns neither the living, nor the dead--the first, because they are still living, the second, because they are not living any more.

Prodicus was known in holding a theory of the origin of religion. According to Prodicus, in the beginning human beings worshipped as gods the sun, moon, rivers, lakes, fruits, etc., the things which were considered to be the sources of their foods and life. As an example of it, Prodicus referred to the cult of Nile in Egypt. The second stage would be that in which the inventors of various arts, agriculture, viticulture, metal work, etc. were worshipped as the gods: Demeter, Dionysus, Hephaestus, etc.
According to this view, the prayer (the worshipping ritual) should be superfluous, so Prodicus got in trouble with the authorities in Athens.
Like Protagoras, Prodicus was also noted for his linguistic studies and wrote a treatise on synonyms.

Hippias of Elis

Hippias of Elis was a younger contemporary of Protagoras and was well known for his versatility in knowledge. Hippias was excelled in mathematics, astronomy, grammar and rhetoric, rhythmics and harmony, history and literature and mythology.
At one of Olympic Games, he was recorded that he declared that all of his clothes were made by himself.
His list of the Olympic victors laid the foundation for Panathéneia - the later Greek system of dating by means of the OLympic Games which had been first introduced by the historian Timaeus.
In Plato's dialogue Protagoras, Hippias maintained:

Law being the tyrant of men, forces them to do many things contrary to nature.

This may be often construed as saying that the law of the city-state is often too narrow and very arbitrary as well as tyrannical, so the human made law is essentially different from the natural laws (agraphoi nomoi).

Gorgias of Leontini ( 483 - 375 B.C.)

Gorgias was born in Leontini of Sicily around 483 and died in 375 B.C., as we mentioned in connection with Empedocles.
Gorgias was supposed to be Empedocles' best student in rhetoric.
When he already established himself as a polished, eloquent speaker, he was chosen by his native city state, Leontini, to seek the military support for his native state against the threat of Syracuse. Athens' imperialistic influences extended not only to East Greece, but also to West Greece as well. In 427 B.C.Gorgias, therefore, came to Athens as a diplomat with the mission to change Athens' diplomatic policies of non-interference and to send her navy to Leontini to fight against Syracuse. Although nobody expected his success, Gorgias was able to change the Athenians' policies and secure their support for Leontini.
Later a revolution (coup d'etat) took placed in Leontini and Gorgias was forced to take refuge to Eastern Greece as a teacher of eloquence or rhetoric and visited Athens several times as well.He was supposed to have written a book on Optics.
It was also known that, under Zeno's influences (?), Gorgias became a skeptic and wrote a book on Non-being or Nature (Peri tou mé ontos hé peri physeos). Although the original was lost, his main thought may be found from Sextus Empiricus and from the pseudo-Aristotelian writing On Melissus, Xenophanes and Gorgias.
According to these writings, Gorgias apparently reacted to the Eleatic philosophies in a sense differently from Protagoras. On the one hand, Gorgias may be considered as the philosopher who radicalized Protagoras' thoughts one more step. Protagoras' thesis appears to be more epistemological and ethical in its nature, while Gorgias seemed to assert his thesis on the basis of his own ontology, namely, that nothing exists. On the other, Gorgias may be viewed perhaps as maintaining the opposite to Protagoras' thinking which held that everything is true (to everybody).

1) "Nothing exists":
For if there were anything then it would have either to be eternal or to have come into Being. But it cannot have come into Being, for neither out of Being nor out of Non-being can anything come to be.
Nor can it be eternal, or if it were eternal, then it would have to be infinite.
But the infinite is impossible for the following reason. It could not be in another, nor could it be in itself, therefore it would be nowhere. But what is nowhere, is nothing.
2) "If there were anything, then it could not be known."
For if there is knowledge of Being, then what is thought must b e, and Non-being could not be thought al all. In which case there could be no error, which is absurd.
3) "Even if there were knowledge of bering, this knowledge could not be communicated (i.e., imparted)."
Even sign is different from the thing signified; e.g.
how could we impart knowledge of colors by word, since the ear hears tones and not colors?
And how could the same representation of being be in the two persons at once, since they are different from one another?"

These theses of Gorgias were taken by some as a seriously philosophical nihilism, while the other took these as jokes, as Gorgias could skillfully argue both pro and con. Nevertheless, the latter view (i.e., taking Gorgias' thought as a joke) seems not compatible with the fact of Isocrates' historical treatment of Gorgias that Isocrates put Gorgias' thought besides Zeno and Melissus, nor with the writing Peri ta Gorgiou (On Gorgias' Thoughts), which treats Gorgias' ideas seriously.
Together with Protagoras relativism, Gorgias' contentions no doubt provided the philosophical foundation for the interpretation of sophistic "wisdom" and the justification for the sophistic activities.
According to Gorgias, the rhetoric was the mastery of the art of persuasion, that should further lead him to a study of psychology. Gorgias deliberately practiced the art of suggestion (hé psychagogia), which could be used for the practical usefulness and for artistic purposes. On the basis of this, Gorgias further developed the art of justifiable deception (hé dikaia apaté), calling a tragedy "a deception which is better to cause than not to cause; to succumb to it shows greater powers of artistic appreciation than not to." This can be well compared to Aristotle's theory of tragedy by means of hé katharsis.
The fact that Plato ascribes the doctrine of might-is-right to Gorgias student Callicles, while another disciple, Lycophron, asserted that nobility is a sham and the all men are equal, and the law is a contract by which right is mutually guaranteed, while yet another student demanded the liberation of slaves in the name of natural law, some scholars believe that Gorgias renounced philosophy and declined to discuss the questions of truth and morality.

Thrasymachus of Chalcedon

Thrasymachus was vividly described by Plato in his Republic Book I, where he appeared as a forerunner of Machiavelli's social and political philosophy, namely Thrasymachus was a realist. According to Thrasymachus, people and philosophers talk about right and jsutice as if they were high ideals, but in actual stiutations and in the real circustances of politics, what actually happens was that the power indeed counts and nothing else. What is considered justice is no other than that which profits the politically powerful and the ruler. That are what in reality they call "right" and "justice."
Thus, Thrasymachus argued against Socrates:

The might makes right.
and
Justice is the advantage of the stronger.

Antiphon of Athens

Antiphon was a native Athenian, that was an exception to the rule, as most sophists were foreigners to Athnes.
Antiphon was known by his thesis of the equality of human beings.

All human-beings are equal.

So he denounced the distinction between the nobles and the commons, Greeks and barbarians, as he contended such a distinctions were due to the philosophical barbarism.
Antiphon made education of the youth be the most important thing in life and the society. He even created the literary genre of hé techné arupias logoi paramythétikoi, and boasted that he could free anyone from any sorrow by oral means.
Antiphon also contended that the human made laws are conventions and said:

In the face of others, one should follow the right and the wrong of the nomos,
while being alone and private, one can follow one's own right and wrong (= one may disregard social norms and moral rules which are nomoi).


Nomos and Physis

The great problem which had in fact prepared for the sophists, Socrates, Plato and Aristotle to pay more attention to Human-being Himself and His questions was the not only the relativism of truth and the destruction of knowledge being universal and necessary, but the collapse of and the loss of the confidence of the people in the absolute and universal validity of the moral standard and authority among human-being affairs.
Through the wars and the contacts with other city states and even other cultures, people became forced to be aware the distinction between what is in nomos (en nomo)and what is in physis (en physei).
What is this distinction and what is physis and what is nomos?
What is in physis means the thing of nature which occurs by necessity and is universally the same wherever it occurs and whenever it occurs. The natural phenomenon.
On the contrary, the "nomos" primarily meant "law." While the laws of the city state was considered earlier (than the 5th Century B.C.) to be god-given, absolutely and necessarily valid as well as universal. Through cultural metamorphoses such as wars and coups d'etat, etc., the laws first of all were discovered to be human-being-made thus not universal and necessary. Bedsides the positive laws of a state, morality,m etiquette, the religion and religious rituals were more and more found to be not god-given, not by nature, but human-being-made and nominal (onoma = names only).
Prior to this application to values and cultural social phenomena, this distinction between physis and nomos had been introduced primarily by the natural philosophers concerning their understanding of nature.
Parmenides, for example, said that change and motion existed only in "opinion" (hé doxa = hé onoma).
Empedocles said that generation and corruption took place in nomos (en nomo).
Leucippus and Democritus advocated that what really (in physis = en physei) existed were atoms (to atomon = the no longer divisible material units) and void (to kenon), while shape, taste, color, smell, etc. all sensations are existed only in human-being nomos.
Now this opposition between nomos and physis was introduced into the human-being sphere of social, cultural affairs and created relativism in values, culture and society: There is nothing absolute, but everything is relative, relative to a given society, relative to a family and relative to an individual.
According to Archelaos, beauty and ugliness, moral good and evil, shame and honor, right and wrong exist not in themselves, but exist only in human-being nomoi.
Hippias said that in physis (en physei), human-being is equal, while in laws (en nomoi), human-being is not equal. Here we see the origin of thought in the French Enlightenment Movement, represented by Jean Jacques Rousseau.
According to Callicles, morality exists in physis (en physei), but in laws (en nomoi) the strong win and take more, while the weak lose and get less. In this case, "en physei" is understood as the true ideal of morality, while "en nomoi" is understood as the real state of affairs in morality and politics.

What does this opposition of which the Greek more and more became conscious actually mean?
This opposition was resulted from the fact that the Greek widened their knowledge, experience a revolution or a coup d'etat, and wars. As a consequence, one set of laws and morality was enforced, the other were rejected. They became aware of the relative nature of actual morality and social practice.

Dissoi logoi:
It is possible to argue the pros and the cons regarding every issue and matter. Whether this is the result or the cause of the distinction of nomos and physis is not known, but it was inseparably associated with this sophists' activities.
For example, an Athenian mother attempts to persuade her son not to enter politics:

If you say what is just, men will hat you; and if you say what is unjust, the gods will hate you; but you must either say the one or the other; thereore you will be hated!

Her son rebutted Mother's argument as follows:

If I say what is just, the gods will love me; and if I say what is unjust, men will love me. I must say either the one or the other. Therefore I shall be loved!

Euathlus wanted to learn how to argue successfully, but he had no money to pay the high fees demanded by many sophists. Protagoras, recognizing his talent, accepted Euathlus as his student with a certain condition which purports that Protagoras would teach Eutahlus but he would not receive the tuition fees until Euathlus wins the first court case. Upon completion of his study with Protagoras, Euathlus did not start practicing his law. So tired of waiting, Protagoras took him to the court, where Euathlus defended himself. Protagoras argued:

If Euathlus loses this case, then he must pay me (by the judgment of the court); if he wins this case, then he must pay me (by the terms of the contract). He must either lose or win this case. Therefore, Euathlus must pay me!

Euathlus argues against Protagoras as follows:

If I win this case, I shall not have to pay Protagoras (by the judgment fo the court); if LI lose this case, I shall not have to pay Protqagoras (by the terms of the contract, as I have not yet won my first case). I must either win or lose this caswe. Therefore, I do not have to pay Protagoras!

These dissoi logi are today called "dilemma" and often used as exercises for rhetoric.

Cultural Anthropological Findings
An example may be found in the relativistic cultural anthropological finds: in Sparta, girls do physical exercises including contact sports, arms uncovered and with underwear, while in Ionia it is considered against etiquette and manner. In Sicily the girls were forbidden to love someone before the marriage, while in Athens it, was forbidden both before and after the marriage. In Trachea, the girls were tattooed, while in the Greece only the criminals were tattooed, etc.
As mentioned before, Antiphon also contended that you should follow the right and wrong of the nomos in the face of others, while being alone and private, you follow your own right and wrong.

Relativism
Critias, the leader of the dictatorship in Athens at 404 B.c., is said to have said that human-beings invented gods in order to have men act right even in privacy and alone, but gods were imaginary products of human-beings!
Thus, the state religion, the laws of the state, morality, etiquette, and manners, social orders and political organizations had to experience a deep crisis in the face of this opposition of nomos and physis as to their authority previously considered as absolute, unquestionable and universal.
Different city states have different nomoi, the same polis experiences revolution and different hierarchy of values.
After the collapse of the sate religion, the state laws, the sate morality in their absolute authority, the universality and absoluteness of the laws, the religion, the morality etc. became the question of the philosopher.
It was precisely Socrates that took upon himself this mission, this search for reestablishing these universal values, laws and morality and religions.