Historical notes on Scepticism
Overview
Scepticism has a long history.
Ancient and modern scepticism in a nutshell.
There was a great deal of sceptical thought in ancient Greece before scepticism became a self conscious philosophical stance. Here are one or two examples.
Socrates and Plato contributed some significant elements to the development of sceptical thought, without themselves being full-blooded sceptics.
Scepticism proper may be considered as falling into four principle stages, the practical scepticism of Pyrrho of Elis, academic scepticism, pyrrhonean scepticism, and empiric scepticism.
Academic scepticism is that of Plato's academy and occurs in several phases.
A pyrrhonean sceptic is one whose doubts are universal and who therefore makes no claims to knowledge.
During the sixteenth and seventeenth centuries, from the beginning of the reformation to the dawn of the enlightenment, pyrrhonean scepticism was a significant influence on European philosophy.
Positivist philosophy in its broadest sense is a general tendency in philosophy which embraces aspects of the thought of many philosophers including Humean scepticism, the work of Comte (who coined the term), elements of utilitarianism and pragmatism, and logical positivism.
Introduction to Sceptical Thought
Ancient and modern scepticism in a nutshell.
Scepticism in Ancient Greece
The word "sceptic" comes from a Greek word which means "seeker after knowledge". It came to be used philosophically for those who sought but failed to find, and hence for those whose doubts, even about the possibility of knowledge, were extreme and pervasive. The term however, is also used in cases of more moderate or less general scepticism.

Sceptical doubts are to be found throughout the history of western philosophy, but philosophers whose philosophy was exclusively or primarily sceptical, and who are therefore called sceptics, appear during just one period in the philosophy of ancient Greece. This period begins in Plato's Academy after the death of Plato (348 BCE) with the "Academic Sceptics" and is taken up by Pyrrho of Elis (360-270 BCE) and runs through until comprehensively documented five centuries later by Sextus Empiricus (c. 160-210 CE).

In its most extreme form Greek scepticism doubted that our experience of the world (or anything else) yielded any knowledge, all one could know was that things appear to be as they appear to be, "appearances appear". Not only do we not have any definite knowledge, according to the most extreme pyrrhoneans, but no proposition can be properly regarded as more probable than its negation. This yields the notion of "equipollence". It was an objective of some sceptics to demonstrate of any proposition allegedly known to be true, that it could not be known even to be more probable than its negation.

Such sceptics termed their opponents, those who were prepared to assert the truth of any proposition, "dogmatists".
Modern Sceptical Thought
In "modern" philosophy (i.e. since Descartes) the two most important kinds of sceptical thought are systematic doubt and positivism.
  • Systematic doubt is the method used by Descartes, who so doubted the knowledge of his contemporaries that he thought it desirable to raze the entire structure to the ground and begin again with a clear slate. This is scepticism about received opinion as a prelude to the construction of a dogmatic philosophical system.
  • positivism is another kind of limited scepticism which is married with a constructive program. In this case the most prominent element of the scepticism is scepticism about the senses, and the constructive element involves some conception of proper scientific method, often combined with the reformulation of scientific theories in phenomenalistic terms. These phenomenalistic reformulations may be seen as a modern variant of the pyrrhonean view that we can know only about appearances, not about anything we might suspect to be an external cause or subject of those appearances. The prototype of positivistic scepticism is David Hume, its first prophet Auguste Comte.
Pre-Socratic Scepticism
There was a great deal of sceptical thought in ancient Greece before scepticism became a self conscious philosophical stance. Here are one or two examples.
1. Heraclitus
Possibly the earliest philosopher thought to have had sceptical leanings was Heraclitus, the instigator of that most elementary source of scepticism mistrust of the senses. Heraclitus believed that all is change and strife and that good and evil are one. He advocated introspection as a source of truth.
3. Zeno of Elea
Zeno of Elea was a student of Parmenides who showed particular agility in finding rational arguments to support Parmenidian doctrines. Though his motivation seems to have been dogmatic rather than sceptical, his way of supporting Parmenidian doctrine seems primarily to have been by undermining the principle opposition, Pythagorean pluralism. He provides the clearest and most incisive early examples of a method which was to become the hallmark of Pyrrhonean scepticism, that of undermining a dogmatic opponents position by assuming it to be true and deductively deriving a contradiction. His most famous paradox is that of Achilles and the tortoise in which is argued that Achilles can never overtake the tortoise. As well as this (perhaps unintentional) contribution to the armoury of subsequent sceptics, Zeno's arguments contributed to the sense of disillusion with pre-Socratic metaphysics which paved the way for the more sceptical tenor of the Sophists.
2. Parmenides
Parmenides was, by contrast with Heraclitus, sceptical about the possibility of movement or change of any kind. Clearly he must have disbelieved his senses. He takes one step further than Heraclitus by sourcing his doctrine, not on mere introspection, but on reason. In this he may be the first precursor for that kind of scepticism found for example in David Hume in which demonstrative proof is taken to be the only source of certain knowledge.
4. Protagoras and the Sophists
Bertrand Russell, in his History of Western Philosophy Russell46 locates the beginning of scepticism and of a decline in the vigour of Greek philosophy, with Protagoras and the sophists. Protagoras observed that "Man is the measure of all things ...", which is usually taken as a radical relativism, denying objective truth and hence as essentially sceptical (and, Russell suggests, based on the 'deceitfulness' of the senses).

The most explicitly sceptical of the sophists appears to have been Gorgias, who maintained that:
  • nothing exists
  • if anything did exist, we could not know it
  • if anything could be known, we could not communicate that knowledge
and went on from there to devote himself to rhetoric.

More generally, in the sophists rhetoric becomes more highly valued than the search for truth or wisdom.
Socrates and Plato
Socrates and Plato contributed some significant elements to the development of sceptical thought, without themselves being full-blooded sceptics.
Socrates
One of Socrates' best known statements is to the effect that he is wiser than others only by virtue of knowing his own ignorance. It is possibly this kind of generally sceptical observation which made Cicero attribute his own view that nothing could be known (except that almost nothing can be known) to Socrates.

Socrates does deploy to great effect, if Plato's Socratic dialogues are veridical, the method of refutation by reductio absurdum which is later systematised in the Pyrrhonean tropes. But the Socrates presented by Plato is by no means universally sceptical, he is devoted to demonstrating the truth of a broad ranging systematic philosophy.
Plato
Plato's scepticism is conspicuous in the most fundamental part of his philosophy, the theory of forms, which is justified and explicated in his simile of the cave and is based on scepticism about the senses. Plato's realm of forms is one of which we can obtain reliable knowledge, through reason, of intelligible objects, by contrast with the unreliable knowledge of the world of appearances which we obtain through our senses.

This is a specific area of scepticism, though fundamental in Plato's philosophy, not the kind of broad all encompassing scepticism found in the academic and pyrrhonean sceptics.
Greek Scepticism Proper
Scepticism proper may be considered as falling into four principle stages, the practical scepticism of Pyrrho of Elis, academic scepticism, pyrrhonean scepticism, and empiric scepticism.
Pyrrho and Timon

Pyrrho of Elis (c. 360-275 BCE) was reputed to have espoused and practised scepticism as a way of achieving peace of mind. It is doubtful that he was a pyrrhonean sceptic as that term has come to be used, but he was adopted as figurehead by the later pyrrhonean sceptics.

Timon of Phlius (c 315-225 BCE) "sat under" Pyrrho (among others) and adopted his sceptical attitudes if not his ascetic lifestyle. He was perhaps best known for his popular Lampoons in which he poetically derided the views of the dogmatic philosophers.

Academic Scepticism

The academy founded by Plato, during the period when Arcelisas of Pitane (c. 315-241 BCE) was its principal to that in which Carneades of Cyrene (c. 213-129 BCE) held that position adopted a sceptical position in which the central doctrine was the rejection of the Stoic epistemology (which admitted the possibility of definite "apprehension" of objects via a special kind of sense impression, sometimes called "cataleptic" impressions).

Pyrrhonean Scepticism

Pyrrhonean scepticism is a form of scepticism inspired by Pyrrho of Elis and developed primarily by Aenesedemus (c. 100-40 BCE) and Agrippa (maybe first century AD), and later written up by Sextus Empiricus (c 160-210 BCE).

The emphasis in Pyrrhonean scepticism is on the suspension of judgement, originally (in Pyrrho himself) as a way of achieving peace of mind. It is also probably in this school that the name "sceptic" (someone seeking knowledge) comes to be used, since the pyrrhoneans purport (perhaps somewhat disingenuously) to be continuing to search for knowledge but failing in their search and finding it necessary in all cases to suspend judgement.

The clearest evidence of duplicity in pyrrhonean scepticism is that the pretence to be seeking knowledge sits alongside the clear articulation (by Sextus Empiricus) of the ends and means of scepticism, which are respectively the achievement of peace of mind, and the suspension of judgement. Thus the pyrrhonean sceptic, far from seeking knowledge, is intending to achieve peace of mind by effecting an indiscriminate suspension of judgement.

Apart from noting this inconsistency in the doctrine, we may disagree with the supposed summum bonum and doubt that the proposed means will realise that end.

Empiric Scepticism

There appear to have been three schools of medicine which were respectively dogmatic, sceptical (empiric) and pyrrhonean (methodic), i.e. drawing conclusions about ultimate causes of illness, denying that such causes are "apprehensible" (empiric) and suspending judgement on the apprehensibility of ultimate causes (methodic). Sextus Empiricus seems to have been (or have begun as) a methodic.

Possibly empiric scepticism may be thought of as a precursor of modern empiricism and positivism.

Academic Scepticism
Academic scepticism is that of Plato's academy and occurs in several phases.
The term "academic" here refers to the academy of Plato which gradually adopted academic scepticism after the death of Plato.

It is common, even today, casually to dismiss the sceptic on the grounds that he is inconsistent in claiming to know that no knowledge is possible. This argument is so simple that there can have been few sceptics who were not aware of it. It was certainly known (if not known certainly) early in the history of Greek scepticism.
A simple, if perhaps somewhat ad hoc escape from this charge is to admit one exception, claiming to know that nothing can be known except that nothing but this one proposition can be known. Apparently Cicero took this position and attributed it to Socrates, though this attribution is conspicuously contradicted by Plato (if his Socratic dialogues are to be taken as historically accurate).

Academic sceptics who made no exception are said to include Arcesilas and Carneades. I don't know how they deal with the allegation of inconsistency. One possibility is to express belief without claiming knowledge. "I believe, but do not know, that no knowledge is possible.". Better, perhaps, to avoid even a statement of belief and be content with an expression of doubt "I doubt that knowledge is possible".
Arcelisaus

Arcelisaus was the first head of the "Middle" Academy, and devoted much energy to disputing with the Stoics against their epistemological doctine that knowledge is based on so-called "cataleptic" impressions, which according to the Stoics could be known to be veridical in virtue of their vividness and distinctness.

A point of controversy in relation to Arcelisaus is whether his scepticism was consistent with the exigencies of everyday life, with the beliefs supposed to be essential to personal survival. This criticism is offered against Arcelisaus by Colotes. Plutarch defends Arcelisaus against Colotes in the following way. Firstly, Plutarch attributes to Arcelisaus the view that the soul has three "movements", sensation, impulse and assent. Arcelisaus allows both sensation and impulse, deprecating assent and opinion. Distinguishing impulse from assent allows Arcelisaus to allow that a philosopher act judiciously merely be impulse, without the need for assent to dogmas or opinions which might justify the action.

In support of this we may also consider the way of Dao, in which the principle "wu wie" prefers spontaneity, acting from the center (without acting). (Dao also involves the idea of unity of opposites ("Yin Yang") which connects with the sceptical propensity (after Socratic method) of arguing both sides of each question).

Carneades

Carneades, while rejecting the possibility of demonstrative knowledge allowed that one might nevertheless have opinions of various degrees of strength and that our actions should be based on such opinions. He adopted plausibility as a practical criterion and distinguished between impressions which are:

  1. implausible
  2. plausible (i.e. appear true "to an intense degree")
  3. irreversible (i.e. plausible and confirmed by other impressions)
  4. tested (i.e. irreversible and tested by the scrutiny of surrounding circumstances)
Scepticism at this stage is not specifically a doctrine about "knowledge", other kinds of propositional attitude being relevant, the dispute with the Stoics centring on the possibility of "apprehension", which looks more like a relation between a person and an object (yielding perhaps what Russell would have called "knowledge by acquaintance").

Pyrrhonean Scepticism
A pyrrhonean sceptic is one whose doubts are universal and who therefore makes no claims to knowledge.
Intro
The most extreme and systematic scepticism in the philosophy of the ancient Greeks was that of Pyrrho of Ellis and the sceptical tradition which followed him. Pyrrho added moral and logical scepticism to the scepticism with regard to the senses which had preceded him, and is said to have held that there could never be any rational ground for preferring one course of action over any other.

The most thorough and consistent sceptic reserves judgement on all matters, save perhaps that "appearances appear", and this attitude is echoed in those positivist philosophers who advocate that science should do no more than record the results of experiments. Because positivists often have this element of sympathy even for extreme scepticism I propose here to discuss such scepticism in ways which are perhaps better informed by positivist than pyrrhonean philosophy.

In the parlance of sceptics a dogmatist is anyone who has a definite belief. There is of course a risk for sceptics of slipping into dogmatic scepticism by asserting that nothing can be known (except perhaps the content of our sensory experience), and this tendency is also evident in some positivist philosophers.
Lack of Absolute Certainty
It may be argued that we lack knowledge of the external world because our conclusions about it are derived from the evidence of our senses, which is unreliable, but more important, which, reliable or not, does not logically entail any conclusion about the external world. It is logically possible that our senses should yield information which is entirely disconnected with the condition of the world, that they do not, however reliably, is contingent. In this argument is implicit the presumption that to have knowledge of a proposition we must be possessed of evidence which logically entails the proposition under consideration.
Skepticism with regard to the senses
This is an important kind of scepticism for positivism, and is prominent in the philosophy of David Hume. It can be described in foundationalist terms by observing that our knowledge of the external world is derived entirely from the data provided to us by our sense, but even the most simple judgements of perception go beyond what is given to us by our senses. Some kind of process
Some Terminology
These are Greek words except where otherwise noted.
dogma
an opinion, belief, notion, decision, judgment, or public decree
Nescio
(Latin) I do not know. Used by Peter Suber as a name for a particular kind of sceptic (what he takes as the true model of pyrrhonism).
Nesciam
(Latin) I will not know. Used by Peter Suber as a name for another kind of sceptic (a disingenuous pyrrhonean).
epoche
suspension of judgement
ajudice
non-judgement ("English" coined by Peter Suber)
arrepsia
equipoise of a balanced scale
aoristia
to be undecided, indeterminate, uncertain, without definite ideas
aphasia
a speechlessness arising from epoche
ataraxia
a peace of mind supposedly consequent on epoche
isosthenia
of equal strength
equipollence
english word often used to translate isosthenia
Scepticism before the Enlightenment
During the sixteenth and seventeenth centuries, from the beginning of the reformation to the dawn of the enlightenment, pyrrhonean scepticism was a significant influence on European philosophy.
Savonarola
Savonarola is sometimes cited as the first figure in the revival of scepticism. His contribution (apart from denying the authority of the Pope and being executed for his perspicacity) was to have commissioned translations from Greek into Latin of the writings of Sextus Empiricus (which were probably never completed), with which he was acquainted only indirectly (not being proficient in the Greek language).
Michel de Montaigne

Montaigne was the most influential figure in the revival of scepticism.

The pyrrhonean centrepiece of his writing was an extended essay, "Apologie de Raimond Sebond". Sebond argued that the truths of faith can be rationally demonstrated. Somewhat disingenuously Montaigne pretended in his "apologie" to defend Sebond, which he did, despite deploying pyrrhonean scepticism to destroy Sebond's arguments, by arguing that pure faith was the primary basis for religious belief with rational considerations coming a poor second.

Metaphysical Poets

It seems odd to count metaphysicians as sceptics, but this is what Margaret Wiley does in [Wiley52],

The point of interest to her is the combination of scepticism in these poets with religious faith. The scepticism was probably both with respect to the dogmatic religious controversies of the time and also in respect of any tendency for growing scientific knowledge to impinge on the domain of personal faith.

Bayle

Bayle's scepticism seems to have been fairly general though he did have a particular concern with dogmatic religious controversy. He believed human reason better adapted for discovering errors than for establishing positive truth. He thought reason incapable of establishing the existence of god, rather that his existence was repugnant to reason, thereby establishing faith as a greater accomplishment than it might otherwise have been. He considered morality to be independent of religious belief, as powerfully motivated by non-religious belief as it might be by religious beliefs, and more generally doubted the connection between belief and practice.

Notes on the History of Positivist Philosophy
Positivist philosophy in its broadest sense is a general tendency in philosophy which embraces aspects of the thought of many philosophers including Humean scepticism, the work of Comte (who coined the term), elements of utilitarianism and pragmatism, and logical positivism.
Key Elements of Positivism
Kolakowski decribes positivism as "a collection of rules and evaluative criteria referring to human knowledge" which tells us what kinds of proposition might count as knowledge of the world and gives norms for what questions are meaningful.

Four features enumerated by Kolakowski as characteristic of positivism: phenomenalism, nominalism, status of value judgements, unity of science. However, Carnap's logical positivism is neither phenomenalistic nor nominalistic.
Other Aspects of Positivism
Other features which may be present, such as empiricism, scepticism, semantic doctrines (verification, utility, pragmatics), methodology for science and philosophy, foundationalisms.
Scepticism has a long history.
Medieval Precursors
The views of some late medieval philosophers may be said to have elements of positivism in them, and contributed towards the separation of scientific knowledge from metaphysics and a separation of secular from ecclesiastical matters.
Precursors in the Enlightenment
According to Kolakowski, "the Enlightenment had a positivism all of its own".
David Hume
Hume scores well on all of Kolakowski's key features and is therefore considered the first full blooded positivist.
Auguste Comte
Comte is the founding father of positivism, the first to deliberately formulate a positivist philosophy and the person who gave the position its name.
My notes on the book by Leszek Kolakowski.


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