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Introduction | History of Skepticism | Criticisms of Skepticism | Types of Skepticism
Introduction Back to Top

Skepticism (or Scepticism in the UK spelling), also known as Pyrrhonism or Pyrrhonic Skepticism after the early proponent Pyrrho of Elis, is the philosophical position that one should refrain from making truth claims, and avoid the postulation of final truths. This is not necessarily quite the same as claiming that truth is impossible (which would itself be a truth claim), but is often also used to cover the position that there is no such thing as certainty in human knowledge (sometimes referred to as Academic Skepticism).

The term is derived from the Greek verb "skeptomai" (which means "to look carefully, to reflect"), and the early Greek Skeptics were known as the Skeptikoi. In everyday usage, Skepticism refers to an attitude of doubt or incredulity, either in general or toward a particular object, or to any doubting or questioning attitude or state of mind. It is effectively the opposite of dogmatism, the idea that established beliefs are not to be disputed, doubted or diverged from.

In philosophy, it can refer to:

  • an inquiry
  • the limitations of knowledge
  • a method of obtaining knowledge through systematic doubt and continual testing
  • the arbitrariness, relativity, or subjectivity of moral values
  • a method of intellectual caution and suspended judgment

The early Greek Skeptics criticized the Stoics, accusing them of dogmatism, and argued that the logical mode of argument was untenable, as it relied on propositions which could not be said to be either true or false without relying on further propositions (the regress argument), so that every proposition must rely on other propositions in order to maintain its validity. In addition, the Skeptics argued that two propositions could not rely on each other, as this would create a circular argument.

Such logic, they argued, was thus an inadequate measure of truth which could create as many problems as it claimed to solve. However, they believed that truth was not necessarily unobtainable, but rather an idea which did not yet exist in a pure form. So, rather than denying the possibility of truth, the Greek Skeptics merely claimed that logicians had not yet discovered truth, and intentionally remained tentative and continued their inquiry. They also questioned accepted knowledge, and viewed dogmatism as a disease of the mind.

Global Skepticism (or Absolute Skepticism or Universal Skepticism) argues that one does not absolutely know anything to be either true or false. Academic Global Skepticism, therefore, seems to require that absolutely nothing can be known, except for the knowledge that nothing can be known. Others try to maintain some philosophical rigor by claiming to be merely reasonably certain that Skepticism is true, while never asserting that Skepticism itself can be known to be true with absolute certainty. Local Skepticism denies that people do (or can) have knowledge of a particular area or subject (e.g. religion, ethics, morality).

Skeptics oppose Foundationalism (the idea that some basic beliefs that are self-justified or beyond justification) in that they argue that the belief in something does not necessarily justify an assertion of knowledge of it. It has been said of the early Skeptics that they "asserted nothing, but only opined". They pitted one dogmatic philosophy against the next in order to undermine belief in the whole philosophic enterprise, and to encourage an aversion towards what they considered arbitrary and inconsequential babble.

History of Skepticism Back to Top

Philosophical Skepticism originated with the Skeptic school of ancient Greece. Pyrrho of Elis, who traveled and studied as far as India, propounded the adoption of what he called "practical skepticism". He became overwhelmed by his inability to determine rationally which of the various competing schools of thought of the time was correct. Upon admitting this to himself, he finally achieved the inner peace (or ataraxia) that he had been seeking (and which became the ultimate goal of the early Skeptikoi).

However, even earlier than this, Gorgias claimed that nothing exists; or, if something does exist, then it cannot be known; or if something does exist and can be known, it cannot be communicated. Gorgias, however, is known primarily as a Sophist rather than as a philosophical skeptic.

Socrates claimed that he knew one and only one thing: that he knew nothing. Thus, rather than making assertions or opinions, he set about questioning people who claimed to have knowledge, ostensibly for the purpose of learning from them. Although he never claimed that knowledge is impossible, he never claimed to have discovered any piece of knowledge whatsoever, even at his death.

Around 266 B.C., Arcesilaus (c. 316 - 241 B.C.) became head of Plato's Academy in Athens, and he strongly changed the Academy's emphasis from Platonism to Skepticism, and it remained the center of "Academic Skepticism" for the next two centuries. One of the best known of the early Greek Skeptics was Carneades (c. 214 - 129 B.C.), who became the fourth Academy scholarch in succession after Arcesilaus in 155 B.C., and who famously claimed that "Nothing can be known, not even this".

During the 1st Century B.C., Aenesidemus rejected many of the theories of the Academy and founded a separate Pyrrhonian Skepticism school, which revived the principle of epoche" (or "suspended judgment") originally proposed by Pyrrho, as a solution to what he considered to be the insoluble problems of Epistemology.

Towards the end of the 1st Century A.D., Agrippa the Skeptic established five tropes (or grounds of doubt):

  • Dissent - the uncertainty of the rules of common life, and of the opinions of philosophers.
  • Progress ad infinitum - all proof requires some further proof (and so on, to infinity).
  • Relation - all things are changed as their relations become changed, or as we look upon them from different points of view.
  • Assumption - the truth asserted is merely a hypothesis or assumption.
  • Circularity - the truth asserted involves a vicious circle.

Later followers of Pyrrho and Carneades developed more theoretical perspectives, and Sextus Empiricus (c. 200 A.D.) in particular incorporated aspects of Empiricism (the idea that the origin of all knowledge is sense experience) into the basis for asserting knowledge. Sextus and his followers considered both the claims to know and not to know to be equally dogmatic, and claimed neither. Instead, despite the apparent conflict with the goal of ataraxia, they claimed to continue searching for something that might be knowable.

Sextus Empiricus listed at least ten modes of skepticism, which can be broken down into three main categories: that of the subjective perceiver (e.g. the powers of the senses and of reasoning may vary across persons); that of the objective world (e.g. the positions, distances and places of objects would seem to affect how they are perceived by a person); and that of the relation between the perceiver and the world (e.g. any given perception will always be perceived within some context or other).

Much of the history of early Christian philosophy is an attempt to superimpose the new religion over Greek and Roman philosophical methods which were based on Skepticism and probable knowledge. So early Christian thinkers such as St. Augustine and Boethius adapted the epistemological traditions of Greece and Rome to demonstrate that one could in fact arrive at certain knowledge at least in matters of Christian religion.

After centuries of religious dogmatism throughout the Middle Ages, Skepticism again resurfaced during the late Renaissance, and particularly during the Age of Reason and the Enlightenment of the 17th and 18th Century. Michel de Montaigne (1533 - 1592) in France and Francis Bacon in England both took as their starting point the skeptical viewpoint that they knew nothing for certain, as did Blaise Pascal and René Descartes, although these early pioneers were careful not to jettison their Christian beliefs. Montaigne in particular was willing to question the conventional wisdom of the time, calling into question the whole edifice of the educational system, and the implicit assumption that university-educated philosophers were necessarily wiser than uneducated farm workers.

Descartes established a methodological skepticism (also known as Cartesian Skepticism) in which he rejected any idea that can be doubted, and then attempted to re-establish it in order to acquire a firm foundation for genuine knowledge. His famous formulation "Cogito, ergo sum" is sometimes stated as "Dubito, ergo cogito, ergo sum" ("I doubt, therefore I think, therefore I am").

Descartes also posited the "dream argument" (one of the most popular skeptical hypotheses), that the fact that it is so difficult to tell whether one is dreaming or not provides preliminary evidence that the senses that we use to distinguish reality from illusion should not be fully trusted. In addition, he hypothesized the possible existence of an evil daemon (or demon), which presents a complete illusion of an external world (including other people) to the senses, where in fact no such external world exists. This idea morphed much later into the brain in a vat thought experiment, in which a brain's perceived experiences, while held in a mad scientist's vat wired up to a super-computer, cannot be distinguished from the real thing.

David Hume, one of the British Empiricists, claimed that "A wise man, therefore, proportions his belief to the evidence", which provided the basis for the maxim of Marcello Truzzi (1935 - 2003) that "Extraordinary claims require extraordinary proof", much later in the 20th Century. Hume argued that even the most basic beliefs about the natural world, or even in the existence of the self, cannot be conclusively established by reason, but we accept them anyway because of their basis in instinct and custom.

Criticisms of Skepticism Back to Top

Some critics have suggested that just because something cannot be proven (e.g. that we are not dreaming, or that sense perception or memory is not reliable), does not necessarily mean that it is not known or that there is no justification in believing it. Descartes wanted absolutely certain knowledge, but that is not the only possibility, and some would argue that well-justified knowledge is sufficient.

Others have argued that Skepticism turns its own claims on their heads because a skeptic cannot be certain that Skepticism is true. Thomas Reid (1710 - 1796), founder of the Scottish School of Common Sense, argued that, if perception and the other cognitive processes are not reliable, then the faculty of reasoning which the skeptic uses is also bound to be unreliable too. So, either the skeptic is right, in which case we cannot trust our ability to reason and therefore cannot trust the skeptic's conclusion; or the skeptic is wrong, in which case again we cannot trust the skeptic's conclusion.

Types of Skepticism Back to Top
  • Moral Skepticism is the belief that moral knowledge is either nonexistent or unattainable.
  • Religious Skepticism (or Theological Skepticism) is Skepticism regarding faith-based claims. It does not necessarily imply either Atheism or Agnosticism. Religious skeptics question religious authority, and are not necessarily anti-religious but are those skeptical of a specific (or all) religious beliefs or practices. Socrates was one of the first religious skeptics, questioning the legitimacy of the beliefs of his time in the existence of the various gods, which in part led to his trial and execution.
  • Metaphysical Skepticism is a type of local skepticism which denies any metaphysical knowledge.
  • Scientific Skepticism (or Empirical Skepticism) is the questioning of the reliability of certain kinds of claims by subjecting them to a systematic investigation using the scientific method (the formulation and testing of hypotheses through observation and experimentation). A scientific skeptic merely seeks likely proof before accepting any knowledge, especially in controversial areas such as health claims, environmental claims, parapsychology, the existence of unproven creatures, etc. So-called Activist Skeptics are a sub-set of scientific skeptics who aim to debunk or expose in public what they see as the truth behind specific extraordinary claims.

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