Forms of Skepticism
by Rebecca Copenhaver

Table of Contents:
1. Global and restricted.

2. Academic and Pyrrhonian

3. Methodological


1. Global and restricted.

While skepticism always questions our ability to gain justified or reliable knowledge, some skeptical positions question our ability to gain justified or reliable knowledge about anything, while others question whether this is possible in particular realms of study, e.g. science, and whether this is possible with regard to particular items of knowledge, e.g. whether we may know that there is an external world, whether we may know that other people possess minds. A skepticism that questions whether we ever have justified or reliable knowledge is global, while one that questions only whether we have justified or reliable knowledge concerning some subset of possible knowledge is restricted. Often, when speaking of a restricted skepticism, philosophers will state just what it is one is skeptical of, for example, they will refer to "skepticism about the external world", or "skepticism about personal identity".

2. Academic and Pyrrhonian.

Often this distinction is drawn by claiming that the Academics held that they knew only one thing, and that was that there is no knowledge, while the Phyrrhonians held that even this statement was too dogmatic and that one could not even know that one could not know.

Academic skepticism is so called because it was a movement in the Academy begun by Plato. Academic skepticism arose in the third century B.C. in response to the Stoics who claimed some knowledge of the real nature of things. Such claims of certain knowledge marked the Stoics out as dogmatists. The Academic skeptics argued against the Stoics by showing that sense perception and reasoning are unreliable and, in addition, that we possess no criterion by which to judge which of our beliefs are reliable or justified. Since these were arguments that were intended to show that we in fact do not possess knowledge, if they are successful, they themselves would count as a kind of knowledge - thus the characterization of Academic skepticism as the position that all we may know is that we cannot know. Academic skepticism is primarily concerned with certainty which they regarded as necessary for knowledge. They thus produced a series of arguments that were intended to show that those things we take to be most certain - that there is a hand before me - were fallible. Since certainty is impossible, so is knowledge.

Pyrrhonian skepticism is named after Pyrrho of Elis. Although he did not write anything, we know of him through the writings of his student, Timon. Pyrrhonian skepticism is marked by a commitment to the suspension of knowledge. They regarded both the Academic and Stoic philosophers as dogmatic, since both made knowledge claims. Rather than argue for the uncertainty of basic sources of information such as sense perception and reasoning, the Pyrrhonian skeptics proceeded through a series of exercises, called tropes, whose purpose was to create the suspension of judgment. Unlike the Academic skeptics, the Pyrrhonians viewed skepticism not as a philosophical position but as a philosophical exercise with a purpose, that of attaining ataraxia. Ataraxia is a difficult word to translate, but it is a state brought about by the contemplation of the tropes in which one ceases to worry about anything that goes beyond appearances and merely accepts the apparent. The notion of 'appearance' used here is best brought out by considering an illusion or hallucination - if one, like Macbeth, hallucinated a dagger, one could question whether there is in fact a real dagger there, but one could not, or at least would not question whether it appeared to you as if there were a daggerthere. Pyrrhonian skepticism was preserved in the writing of Sextus Empiricus and his writings influenced Montaigne and Descartes when skepticism rearose in the late Renaissance/early Modern period as a philosophical problem, after having been disregarded during the middle ages and early renaissance.

3. Methodological

Many people have heard of 'Cartesian skepticism' and assume that Descartes himself must have been a skeptic. He was not. Rather, in the modern period a group of philosophers including Descartes, Mersenne and Gassendi employed methodological skepticism, or what Popkin calls 'mitigated' or 'constructive' skepticism. Global pyrrhonian skepticism arose in the late renaissance and early modern period in a religious context - it was used, by Montaigne for example - to show how humans are incapable of knowledge without the grace of God. These 'new pyrrhonians' embraced extreme skepticism. In part to defend against the corrosive nature of skepticism, and in part because of religious motivations, some thinkers such as Mersenne, Gassendi and Descartes used and elaborated on the ancient Academic and Pyrrhonian arguments in order to distinguish that which may be known from that which may not. In the case of Descartes, he wished to justify scientific (in the very broadest sense) beliefs by first calling them into question using skeptical method and then reestablish them on a foundation of certainty. Methodological skepticism, then, is primarily an anti-skeptical position in which one adopts skeptical methods in order to form knowledge, unusually about some limited set of things (oneself, God, science, the external world).