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Introductory Paragraph

Early Ionic Natural Philosophers

The Pythagoreans

The Eleatics


Later Natural Philosophers

General Character of the First Period in the History of Greek Philosophy

The Sophist


The Followers of Socrates

The Lesser Socratics

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The Old Academy

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Aristotle: Unity of Plato and Aristotle

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The Peripatetic School

Three Leading Post-Aristotelian Schools

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The Epicureans and Epicureanism

The Sceptics

The Common Ground of the Stoics, Epicureans, and Sceptics

Philosophy in Rome: Eclecticism

The Later Peripatetics

The Later Academics

The Later Stoics

General Character of the Second Period

Standpoint and Schools of the Third and Latest Period of Greek Philosophy

Jewish-Alexandrian School


The Eclectic Platonist

Neo-Platonism. Plotinus

Neo-Platonism. Porphyry. Jamblichus

Neo-Platonism. Proclus




B. C. BURT (1852-1915) - Table of contents                        




§ 19 - The Sceptics

Under the term Sceptics are here included the so-called Pyrrhonists, Earlier and Later (to whom alone, often, the term is applied) and the philosophers of the so-called Middle and New Academies; the attitude of these thinkers being essentially the same. The chief of the Pyrrhonists are Pyrrho, Timon of Phlius, Ænesidemus, Agrippa, and Sextus Empiricus; the leading Academicians are Arcesilaus, Carneades, and Clitomachus.

The Pyrrhonists: Lives(1)

Pyrrho, the first of the Sceptics, was an Elean who had imbibed Democritean doctrines from a certain philosopher, Anaxarchus, whom he accompanied to India in the army of Alexander the Great.


From Diogenes Laertius we learn that he was peculiar, even morbid, in temperament, being extremely indifferent and having no sympathy with general human nature. There is no reason to suppose that he especially admire any of the philosophers (Democritus excepted). He is said to have been highly honored by his country and much esteemed by certain philosophers, among them Epicurus. He died in 270 B.C., at the age of ninety.

His eccentricity among the philosophers of his times appears in the one fact (among others) that he left behind him no written works. Diogenes says that he had many disciples but very few of them are now known. Of these may be mentioned Nausiphanes, the instructor of Epicurus, and a certain Timon of Phlius (320-230 B.C), who had been a pupil of Stilpo, the Megarian, and succeeded Pyrrho as leader of the school. Timon had no successor. The Pyrrhonists did not possess the social qualities of other thinkers of their day. Considerably later than these men, i.e., in the first and second centuries A.D., others, styling themselves Pyrrhonists, took up and elaborated the doctrines of Pyrrho and Timon. Of these we mention Ænesidemus of Cnossus (first century), a certain philosopher by the name of Agrippa, and the celebrated Sextus Empiricus (200 A.D.). 


Theories of the Earlier Pyrrhonists

The position of Pyrrho and of Timon, adopted and extended by later thinkers, is that there is no criterion of truth either in sense or in intellect; that, consequently, there is no knowledge, contradictories are equally true (or false), that the true, philosophic attitude of mind is complete suspension of judgment (έποχή). These men, in other words, finding in the realm of intellect the same contradictions that they, like the Eleatics, Heraclitus, Democritus, the Sophists, Plato, and indeed nearly all the earlier thinkers had pointed out in the realm of sense, developed to its limit a principle that had before them not received complete development, even in the theories of the Sophists. But Pyrrho and Timon did not entirely despair of arriving at truth of a certain kind: truth in life, or conduct, they believed accessible. They taught here that the truth is imperturbability of mind (άταραξία), which follows suspension of judgment "like a shadow," and unquestioning obedience to custom and tradition.

The Later Pyrrhonists: The "Tropes".(2)

By the later Pyrrhonists there were advanced against the possibility of knowledge certain special modes of view termed "tropes" (τρόποι). Ten of these, which are attributed to Ænesidemus, are (in substance) as follows: The denying of knowledge on the ground

(1) of the differences in the feelings of animals as regards pleasure and pain, what is injurious or advantageous;

(2) the differences in the "nature and idiosyncrasies of men";

(3) the "difference of the organs of sense";

(4) the "disposition of the subject [the human individual], and the changes in general to which it is liable;

(5) difference in laws and established customs, belief in mythical traditions, conventions of art, and dogmatic opinions";

(6) the "promiscuousness and confusion of objects";

(7) "difference as regards the distance, position, space, and objects in space";

(8) differences as regards the "magnitudes or qualities of things —heat or coldness, speed or slowness, paleness or variety of color," etc;

(9) "frequency or rarity or strangeness of the thing under consideration";

(10) "the fact that all things are known by comparison with others".

In all these cases it is, practically, held that there is ground for suspension of judgment in the fact that, owing to the differences and contrariety of things, it is impossible to apply the law of identity, or conception of uniformity; i.e. it is impossible to think (in the strictest, narrowest sense of the term). For example,—to take the third "trope,"—since an apple is yellow to the sight, sweet to the taste, fragrant to the sense of smell, i.e., since sight, taste, and smell are different and incommensurable, it is impossible to believe that there is in reality anything such as we ordinarily believe an apple (say) to be—" what is seen is just as likely to be something else than reality". To take another example: since "the Persians do not think it unnatural for a man to marry his daughter, but among the Greeks it is unlawful" "and since the Egyptians embalm their dead, and then bury them, the Romans burn them, the Pæonians throw them into the lake," no positive conclusion regarding marriage or the disposal of the dead is possible. The five tropes of Agrippa are these: the disagreement in opinion among men; the logical necessity of proceeding in infinitum in the attempt to arrive at a fixed, first principle; the fact that no object is perceived independently, but always in its relation to something else; the necessity of starting always with hypotheses: the reciprocal nature of proofs, e.g., proving porosity by evaporation and evaporation by porosity.

The impossibility of Demonstration, of a Sign, of a Cause, etc

The possibility of demonstration was denied by the Sceptics on the ground that there are no true indemonstrable premises, and without such all reasoning aiming at ultimate certainty must be a regressus in infinitum. It was denied also that anything could be regarded as a sign or indication of anything else: the invisible obviously cannot be a sign, either of the invisible or the visible; nor can the visible be a sign of the invisible, since the two bear no relation to one another, and finally, there is no need of a sign for the visible. Again, the notion of a cause is a spurious conception. "Cause is something relative. It is relative to that of which it is the cause. But that which is relative is only conceived and has no real existence... However, let us admit that there are such things as causes. In that case, then, a body must be the cause of a body or that which is incorporeal must be the cause of that which is corporeal. Now, neither of these cases is possible; therefore there is no such thing as a cause. In fact, one body cannot be the cause of another body, since both bodies have the same nature; and if it be said that one is the cause, inasmuch as it is a body, then the other must be a cause for the same reason. And in that case one would have two reciprocal causes; two agents without any passive subject. Again, one incorporeal thing cannot be the cause of another incorporeal thing, for the same reason. Also, one incorporeal thing cannot be the cause of a body, because nothing that is incorporeal can produce a body. Nor, on the other hand, can a body be the cause of anything incorporeal, because in every production there must be some passive subject-matter; but as what is incorporeal is by its own nature protected from being a passive subject, it cannot be the object of any productive power. There is therefore no such thing as any cause at all. From all which it follows that the first principles of all things have no reality; for such a principle, if it did exist, must be both the agent and the efficient cause". Motion, the act or possibility of learning, the distinction between good and evil, were likewise found impossible by the later Pyrrhonists.

Pure Negativism of the Pyrrhonists

Pyrrhonism reached its culmination when, it being objected (it would seem, by the Stoics) that the Pyrrhonists were inconsistent in declaring that they knew nothing and yet admitting common fact of experience, or were, even in terms self-contradictory in saying that they knew nothing, because they must know that they did not know, —the Pyrrhonists answered that they admitted fact merely as such, i.e., not as known and demonstrated fact, and that in saying that they knew nothing they merely stated a fact, but did not logically define or demonstrate their position. "We confess," said they, "that we see, and we are aware that we comprehend that such a thing is the fact; but we do not know how we see, or how we comprehend"; or, "while we say that we define nothing, we do not even say that as a definition".

The Middle and New Academies(3)


Arcesilaus (third century B.C.) had been a pupil of the Peripatetic Theophrastus, and of Polemo, Crantor, and Crates of the Old Academy. He was the founder of the Middle Academy, so-called. His philosophical energies were given chiefly to combating the theories of the Stoics. He denied validity to the Stoic idea of perception, or the "cataleptic representation" (φαντασία καταληπτική), basing his denial on the very obvious ground that a false representation might be of sufficient strength to compel assent, as well as a true one; and he reached the position that it was not possible to know anything with certainty —not even that we did not know. In this he agrees with Pyrrho.


  He was, also, in agreement with Pyrrho in holding probability to be the "highest standard for practical life". From Diogenes, who describes him as a "man of very expensive habits," a "sort of second Aristippus," we ought perhaps to infer that in ethics Arcesilaus sympathized with the Cyrenaics; we have, at all events, no reason to think that he was practically or theoretically an advocate of impassivity.


Carneades, the founder of the New Academy (second century B.C.), industriously studied and combated the Stoic doctrines, gave little attention to physics, and was fond of disputing on ethical topics. He was a forcible speaker, and drew many persons, even from other schools, to hear him. He repeats with added illustration the arguments of Arcesilaus and the Pyrrhonists on the worthlessness of the senses and the intellect as criteria of knowledge. The Stoic theology was especially attacked by him. Neither the alleged consensus gentium, nor the alleged design manifested in nature is to him a demonstration of the existence of God; mere agreement of opinion among the majority of the human race proves nothing, and the existence of danger and destruction, folly, misfortune, misery, and crime in the world is sufficient refutation of the supposed fact of a providence. But even admitting the appearance of order in the world, what necessity is there for affirming the existence of a world-soul? The very idea of a God, an infinite personal being, an infinite being possessing the intellectual and moral attributes of man, is untenable. How can God be subject to the changes of sensation, feelings of pleasure and pain? With what reason can he be called brave, magnanimous, prudent? We cannot conceive God as limited or unlimited, corporeal or incorporeal. In short, we cannot think of God under the forms of sense or of intellect without encountering contradiction; we have no right, therefore, to assert positively, as the Stoics do, the being of a God. And there are no gods; nor is divination conceivable, since to "know accidental events beforehand is impossible, and it is useless to know those that are necessary and unavoidable, nay, more, it would even be harmful". Any supposed cases of fulfilment of prophecy are merely cases of accidental coincidence. Further, the human will is free, for there is no proof of the existence of uniform causality in nature, and we know, as a matter of fact, that our decisions are free. Justice is mere expediency. We have no positive knowledge; our only guide is probability. Now, probability is of three grades: mere probability, unimpeached probability, un-impeached and confirmed probability. "The lowest degree of probability is when a notion produces by itself an impression of truth without being taken in connection with other notions. The next higher is when that impression is confirmed by the agreement of all notions which are related to it. The third and highest is when an investigation of all these notions results in producing the same corroboration for all". Assent will be given to no notion in the sense of its being absolutely true, but to many notions in the sense that we consider them highly probable". On ethical questions Carneades was so fully non-committal that not even his nearest disciple got from him any positive view. In this he went beyond all Greek sceptical thinkers, for they, as we have seen, admitted that a norm of conduct was to be found in tradition and custom. Carneades is a representative, therefore, of the most completely developed philosophical scepticism in Greece.


The position of the Sceptics may be described, in a word, as similar to that expressed by the modern phrase "the relativity of knowledge" and is, more than any other in the history of ancient philosophy, allied to the well-known modern philosophical attitude denoted by the phrase. But it would, most probably, be wrong to suppose that the ancient agnostics held to the idea of a real thing-in-itself behind the (supposed) relative and irreconcilable phenomena. They gave up the idea of causation (as we have just seen) with all others, the very idea which, when applied to explain the origin of knowledge, gives rise to the thing-in-itself. By way of general comment, interpretative and critical, we have to notice, in the first place, that there is a certain evasion on the part of the philosophers we have just been considering of the obligation to think everywhere and always as best we can, and a dogmatic assumption that thought has for its only presupposition and principle the notion of identity. In other words, if the Sceptic admits a thing as a fact, must he not accept the consequences of inference from the fact, must he not ask what the fact means? "Facts" are, indeed, not ultimate for philosophical thought but they must be given a meaning, and there is properly speaking, therefore, no such thing as a universal suspension of the judgment. Thought can have no other object than truth or reality; and is there not a certain demand upon thought in facts recognized as facts, i.e., something immediately before the mind, whatever be their content, whether sensible or supersensible? Again, how is suspension of judgment, pure negativity in thought possible? This state of mind, if reflected upon, contains its own negation. It is double-sided; but the Sceptics saw only that side which could present itself in the act of withdrawing, or abstracting, from contradictory phenomena. If the Sceptic's principle is Thought, he must think and let phenomena fall into his scheme as best they may. This the Sceptics did not do; nor did they, on the other hand, take "facts" for what they were worth and by a fair induction, supplemented by reflection, draw a meaning out of them. The nearest approach made to this is contained in Carneades's doctrine of probability, which seems not to have been thought of as a way to the truth for mind, but only as a way to a comfortable mental attitude or a theory adapted to "practical purposes"; which, in other words, contained no other necessity than that which implied the impotency of mind and not the irrational and non-existent character of the thing regarded as the object of knowledge. The Sceptical doctrine, though valid as against uncritical dogmatism (e.g., Stoicism), is not valid as against the position that in human experience, subject and Object, thought and phenomenon, are, by the very nature of the conditions of experience, correlative: not mere identity but identity in difference is the law of real thought. We are not at liberty to ignore fact; we are at liberty, and, in fact, obliged, to follow conceptions, and, among them, the conception of pure thought, to their consequences. Making allowance for a natural difference between sense and thought as forms of mental activity, the meanings of fact should tally with the positings of thought. It might perhaps be said of the theory of the ancient Sceptics, as it was said by a modern Sceptic of his own theory, that it was unanswerable but convinced nobody. But even this need not be said. The Sceptic is not at liberty to suspend the judgment: for on the one hand, he must make the most of facts, and on the other, he must deduce the consequences of a suspension of the judgment, namely, he must accept and understand the fact of mere subjectivity. And this is the service of Scepticism—that it brings this fact to light.


(1) See Diog. Laert, pp. 402-423; Zeller; Ueberweg.

(2) Diog. Laert., Life of Pyrrho, pp. 409-413.

(3) See Zeller; Ueberweg; Diog. Laert., pp 163-170, 177-180.

(4) See Zeller's Stoics, Epicureans, and Sceptics.



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