"Scepticism is an ability to place in antithesis, in any manner whatever, appearances and judgements, and thus -- because of the equality of force in the objects and arguments proposed -- to come first of all to a suspension of judgement and then to mental tranquillity."
-- Sextus Empiricus, Outlines of Pyrrhonism
"Scepticism is the chastity of the intellect, and it is shameful to surrender it too soon or to the first comer: there is nobility in preserving it coolly and proudly through a long youth, until at last, in the ripeness of instinct and discretion, it can be safely exchanged for fidelity and happiness."
-- George Santayana, Scepticism And Animal Faith
"The business of skepticism is to be dangerous. Skepticism challenges established institutions. If we teach everybody, including, say, high school students, habits of skeptical thought, they will probably not restrict their skepticism to UFOs, aspirin commercials, and 35,000-year-old channelees. Maybe they'll start asking awkward questions about economic, or social, or political, or religious institutions. Perhaps they'll challenge the opinions of those in power. Then where would we be?"
-- Carl Sagan, The Demon-Haunted World
"Now, the Sceptic discipline is called the 'zetetic' (searching) from its activity of searching and examining. It is also called the 'ephetic' (suspending) from the experience which the inquirer feels after the search. 'Aporetic' (doubting) is another name for it, either from the fact that their doubting and searching extends to everything (the opinion of some), or from their inability to give final assent or denial. It is also called 'Pyrrhonean,' because Pyrrho appears to us to have applied himself to Scepticism more thoroughly and with more distinction than his predecessors."
-- Sextux Empiricus, Outlines of Pyrrhonism. Quoted in Samuel E. Stump, Philosophical Problems (1983), p. 250.
"Skepticism, the philosophic position which denies the ability of man to know all, and the ability of his reason to penetrate everything. In loose speaking it is sometimes used to mean any questioning attitude. Skepticism challenges the supremacy of reason, and it is at home with supernatural religion, in so far as this maintains itself as mysterious, i.e., impenetrable to reason. The man who questions the assumptions of religion is not a skeptic, but simply an unbeliever. Thoroughgoing skepticism is logically untenable because in denying the possibility of any truth, the skeptic denies the truth of his statement. Skepticism manifests itself very early in the history of Western thought. The Sophists seem to have been the first skeptics. Some of them, like Protagoras, taught the relativity of knowledge -- that "man is the measure of all things." Others were, or attempted to be, absolute skeptics. Gorgias, for instance, held that nothing could be known, or if anything were known, it could not be communicated. Pyrrho later held a similarly extreme position, teaching that reality is inaccessible to us. Arcesilaus of the Middle Academy argued in various ways that certitude is impossible and only probable knowledge is attainable. In the Renaissance, skepticism is seen in the writings of Montaigne and Pierre Charron. Like Charron, Pascal was a skeptic because of his religious views. Pascal held that the existence of God, or at least of a loving God, could not be proved, and urged that only mystical experience can demonstrate Him. A similar position of skepticism is common in Christianity, although it is by no means universal among Christians. In the 18th century the philosophers of enlightenment (e.g., Bayle, Voltaire) were not skeptics, because they assumed the rule of reason or rationalism, of which skepticism is the especial enemy. Voltaire's deism is an extreme of rationalism in religion, just as Pascal's mysticism is an extreme of skepticism in the same. Hume is one of the most famous of modern skeptics, though skepticism is not a characteristic of his thought. In his criticism of basic concepts he sharply limited man's supposed knowledge of substance, causality, the self, and the like. The greatest of modern skeptics is Kant, whose antimonies are an actual demonstration of skepticism, because they show certain problems to be insoluble by reason. As a result, pure modern Kantian agnosticism is closely linked in basis with skepticism. The scientific method demands that all things assumed as facts be questioned and is, therefore, skeptical to a degree; but the positivism of many scientists, whether latent or open, is incompatible with skepticism, for it accepts without question an assumption, namely, that material effect is impossible without material cause. See J.B. Bury, A History of Freedom of Thought; J. Owen, Evenings with the Sceptics; J.M. Robertson, A Short History of Free Thought; M.M. Patrick, The Greek Sceptics."
"Skepticism (from the Greek, skeptesthai, "to examine" or "to consider") is a general name for the philosophic or scientific attitude that rejects claims to certainty. It is thus opposed to dogmatism, an attitude of authoritative certainty. Its basic philosophical contention is that the possibility of knowledge is limited by the limitations of the mind itself or by the inaccessibility of the object. Democritus is generally regarded as the first skeptic; he called the senses into question as a guide to objective reality. During the Hellenic period the Greek Sophists were skeptical of any claims to found ethics on natural rights or objective values. During the classical period Plato's Academy developed skepticism as its official school position; hence the concept of Academic philosophy meant (to Cicero, for example) "skeptical philosophy." This transformation of Plato's thought seems to have come about through an agreement with the need to grasp the Platonic Forms for any kind of certainty, combined with a disagreement as to whether human intelligence can ever attain such a grasp. This Academic view became well known in the West through the writings of Cicero.
Other skeptics during the classical period include Pyrrho of Elis, his follower Timon of Athens (c. 320-230 BC), and, later in Rome, Sextus Empiricus (AD c. 200). Gorgias, the Sophist, in his speech "On the Nature of Things," had first defended skepticism by collecting disagreements among the experts in science and philosophy. Sextus Empiricus developed a similar technique: he showed that the "criterion," the test of certainty advocated by one school, contradicted the certainty of the doctrines of the other schools, each of which had an alternative "criterion."
During the modern period skepticism returned to philosophy again. The humanistic essays of Michel de Montaigne expressed doubt about transcultural absolute norms much as the urbane Greek Sophists had. Rene Descartes used "systematic doubt" as a main tool of his method. David Hume, in his Dialogues on Natural Religion (1779), offered a tentative dialogue in the manner and spirit of Cicero; in his Treatise of Human Nature (1739-1740) and other works he set the tone for contemporary discussion.
One difficulty faced by the skeptic, and one his opponents have never hesitated to point out, is that his claim to absolute uncertainty and doubt sounds just as dogmatic and just as certain as the doctrines of the so-called dogmatists he is criticizing. This consideration led Pyrrho to describe his own position as merely probable and led the Academy just after Cicero's time to give up its positive view in favor of a tepid eclecticism. Twentieth-century philosophers believe that much of the debate has resulted from mistaken and overly simple confusions of the meaning, criteria, and ambiguity of the concept of certainty. -- Robert S. Brumbaugh "
Below is an excerpt of an article on skepticism found in The Encyclopedia of Philosophy.
"Skepticism has been continually attacked and 'refuted' in the history of philosophy and has only occasionally been set forth as a serious view. Opponents have argued from Greek times to the present that skepticism is untenable and that it flies in the face of common sense and ordinary beliefs. As Hume admitted, one of the characteristics of skeptical argumentation is that 'it admits of no answer, and produces no conviction.'
"The skeptics from Sextus Empiricus to Montaigne, Bayle, Hume, and Santayana have pointed out that the strength of skepticism lies not in whether it is tenable as a position but in the force of its arguments against the claims of dogmatic philosophers...
"...skepticism has not functioned in philosophy as merely one more position alongside idealism, materialism, and realism. Instead, it has been like an anonymous letter received by a dogmatic philosopher who does hold a position. The letter raises fundamental problems for the recipient by questioning whether he had adequate grounds for his assertions and assumptions or whether his system is free from contradictions or absurdities. The recipient may try to fend off the attack by challenging whether any philosopher could write the letter without opening himself to similar attacks. By imputing an author, the dogmatist may show the problem involved in consistently stating skepticism, but he does not thereby reply to the arguments in the letter. Skeptical arguments are usually parasitical, in that they assume the premises of the dogmatist and show problems that ensue, on the standards of reasoning of the dogmatist...
"The historical skeptics did not say that they personally regarded everything as doubtful. They distinguished believing various matters from having sufficient reasons for believing them. Regardless of the legends about Pyrrho, the skeptical authors seem to have followed Huet's view that it is one thing to philosophize and another to live, and that many propositions may be philosophically dubious but acceptable or even indubitable as living options. The problem posed by skeptical probing was not what do, or what must, people believe but, rather, what evidence is there for beliefs, and is this evidence adequate?
"From Greek times onward, skepticism has functioned as a gadfly to dogmatic philosophy and as a challenge to keep it honest. The skeptical critique has thrived on the desire to find a coherent and consistent account of our knowledge and beliefs about the world. Had there never been disillusionment about what was accepted as true, skepticism would probably not have arisen. Nevertheless, skepticism has led to continual re-examination of philosophical claims and to new dogmatic systems trying to avoid difficulties in others. This in turn has led to new skeptical attacks and ingenious new criticisms or new versions of criticism. Thus skepticism has been a major dynamic force in intellectual history. And even if many philosophers are now willing to accept Hume's friend Thomas Blacklock's observation that 'the wise in every age conclude, what Pyrrho taught and Hume renewed, that dogmatists are fools,' human folly keeps the quest for knowledge of the ultimate nature of reality going and skeptics keep challenging the latest claims to such knowledge. Without skepticism, we probably could not distinguish enthusiasm, prejudice, or superstition from serious or meaningful beliefs. As Shaftesbury said, after living with Bayle for a while, any views he had that could survive the continuous skeptical onslaught, he regarded as being as valuable as the purest gold. Each age is able to assess the views which are valuable to it only if they are subjected to the same challenge."
-- By Richard H. Popkin
It was six men of Indostan
To learning much inclined,
Who went to see the Elephant
(Though all of them were blind),
That each by observation
Might satisfy his mind.
The First approached the Elephant,
And happening to fall
Against his broad and sturdy side,
At once began to bawl:
"God bless me! but the Elephant
Is very like a wall!"
The Second, feeling of the tusk,
Cried, "Ho! what have we here
So very round and smooth and sharp?
To me 'tis mighty clear
This wonder of an Elephant
Is very like a spear!"
The Third approached the animal,
And happening to take
The squirming trunk within his hands,
Thus boldly up and spake:
"I see," quoth he, "the Elephant
Is very like a snake!"
The Fourth reached out an eager hand,
And felt about the knee.
"What most this wondrous beast is like
Is mighty plain," quoth he;
"'Tis clear enough the Elephant
Is very like a tree!"
The Fifth, who chanced to touch the ear,
Said: "E'en the blindest man
Can tell what this resembles most;
Deny the fact who can
This marvel of an Elephant
Is very like a fan!"
The Sixth no sooner had begun
About the beast to grope,
Than, seizing on the swinging tail
That fell within his scope,
"I see," quoth he, "the Elephant
Is very like a rope!"
And so these men of Indostan
Disputed loud and long,
Each in his own opinion
Exceeding stiff and strong,
Though each was partly in the right,
And all were in the wrong!
So oft in theologic wars,
The disputants, I ween,
Rail on in utter ignorance
Of what each other mean,
And prate about an Elephant
Not one of them has seen!
-- "The Blind Men And The Elephant, "By John Godfrey Saxe (1816-1887)
Here is a short list of history's prominent skeptics.
Pyrrho (c. 360-270 BC). Considered the first great skeptic. None of his writings (if indeed he ever penned anything) is extant. What's known of his life and philosophy has come from the observations and notes of students, most notably Timon of Phlius.
Sextus Empiricus (c. 150-225 AD). Outlines of Pyrrhonism (Hypotyposes); Against the Dogmatists (Adversus Mathematicos).
St. Augustine (354-430 AD). Contra Academicos.
Michel Eyquem De Montaigne (1533-1592). Apology for Raimond Sebond, Montaigne's chief philosophical work and noted study in skepticism.
Rene Descartes (1596-1650). Discourse On Method, and Meditations On First Philosophy.
Pierre Bayle (1647-1706). Two-volume Historical & Critical Dictionary.
David Hume (1711-1776). A Treatise of Human Nature, and Enquiry Concerning Human Understanding.
Hans Vaihinger (1852-1933). The Philosophy of "As If".
George Santayana (1863-1952). Scepticism And Animal Faith.
Albert Camus (1913-1960). The Myth of Sisyphus.
Norman Maccoll, The Greek Sceptics From Pyrrho to Sextus (1869).
Richard H. Popkin, The History of Scepticism From Erasmus To Descartes (1960).
Eduard Zeller, The Stoics, Epicureans, and Sceptics (1880).