---
title: "Philosophical skepticism"
chunk: 3/9
source: "https://en.wikipedia.org/wiki/Philosophical_skepticism"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:37:00.045187+00:00"
instance: "kb-cron"
---

=== Criticism ===
Philosophical skepticism has been criticized in various ways. Some criticisms see it as a self-refuting idea while others point out that it is implausible, psychologically impossible, or a pointless intellectual game. This position is based on the idea that philosophical skepticism not only rejects the existence of knowledge but seems to make knowledge claims itself at the same time. For example, to claim that there is no knowledge seems to be itself a knowledge claim. This problem is particularly relevant for versions of philosophical skepticism that deny any form of knowledge. So the global skeptic denies that any claim is rationally justified but then goes on to provide arguments in an attempt to rationally justify their denial. Some philosophical skeptics have responded to this objection by restricting the denial of knowledge to certain fields without denying the existence of knowledge in general. Another defense consists in understanding philosophical skepticism not as a theory but as a tool or a methodology. In this case, it may be used fruitfully to reject and improve philosophical systems despite its shortcomings as a theory.
Another criticism holds that philosophical skepticism is highly counterintuitive by pointing out how far removed it is from regular life. For example, it seems very impractical, if not psychologically impossible, to suspend all beliefs at the same time. And even if it were possible, it would not be advisable since "the complete skeptic would wind up starving to death or walking into walls or out of windows". This criticism can allow that there are some arguments that support philosophical skepticism. However, it has been claimed that they are not nearly strong enough to support such a radical conclusion. Common-sense philosophers follow this line of thought by arguing that regular common-sense beliefs are much more reliable than the skeptics' intricate arguments. George Edward Moore, for example, tried to refute skepticism about the existence of the external world, not by engaging with its complex arguments, but by using a simple observation: that he has two hands. For Moore, this observation is a reliable source of knowledge incompatible with external world skepticism since it entails that at least two physical objects exist.
A closely related objection sees philosophical skepticism as an "idle academic exercise" or a "waste of time". This is often based on the idea that, because of its initial implausibility and distance from everyday life, it has little or no practical value. In this regard, Arthur Schopenhauer compares the position of radical skepticism to a border fortress that is best ignored: it is impregnable but its garrison does not pose any threat since it never sets foot outside the fortress. One defense of philosophical skepticism is that it has had important impacts on the history of philosophy at large and not just among skeptical philosophers. This is due to its critical attitude, which remains a constant challenge to the epistemic foundations of various philosophical theories. It has often provoked creative responses from other philosophers when trying to modify the affected theory to avoid the problem of skepticism.
According to Pierre Le Morvan, there are two very common negative responses to philosophical skepticism. The first understands it as a threat to all kinds of philosophical theories and strives to disprove it. According to the second, philosophical skepticism is a useless distraction and should better be avoided altogether. Le Morvan himself proposes a positive third alternative: to use it as a philosophical tool in a few selected cases to overcome prejudices and foster practical wisdom.

== History of Western skepticism ==

=== Ancient Greek skepticism ===

Ancient Greek skeptics were not "skeptics" in the contemporary sense of selective, localized doubt. Their concerns were epistemological, noting that truth claims could not be adequately supported, and psychotherapeutic, noting that beliefs caused mental perturbation.
The Western tradition of systematic skepticism goes back at least as far as Pyrrho of Elis (b. c. 360 BCE) and arguably to Xenophanes (b. c. 570 BCE). Parts of skepticism also appear among the "5th century sophists [who] develop forms of debate which are ancestors of skeptical argumentation. They take pride in arguing in a persuasive fashion for both sides of an issue."
In Hellenistic philosophy, Pyrrhonism and Academic Skepticism were the two schools of skeptical philosophy. Subsequently, the words Academic and Pyrrhonist were often used to mean skeptic.

==== Pyrrhonism ====

Like other Hellenistic philosophies, the goal of Pyrrhonism was eudaimonia, which the Pyrrhonists sought through achieving ataraxia (an untroubled state of mind), which they found could be induced by producing a state of epoché (suspension of judgment) regarding non-evident matters. Epoché could be produced by pitting one dogma against another to undermine belief, and by questioning whether a belief could be justified. In support of this questioning Pyrrhonists developed the skeptical arguments cited above (the Ten Modes of Aenesidemus and the Five Modes of Agrippa) demonstrating that beliefs cannot be justified:

===== Pyrrho of Elis =====

According to an account of Pyrrho's life by his student Timon of Phlius, Pyrrho extolled a way to become happy and tranquil:

'The things themselves are equally indifferent, and unstable, and indeterminate, and therefore neither our senses nor our opinions are either true or false. For this reason then we must not trust them, but be without opinions, and without bias, and without wavering, saying of every single thing that it no more is than is not, or both is and is not, or neither is nor is not.

===== Aenesidemus =====

Pyrrhonism faded as a movement following the death of Pyrrho's student Timon. The Academy became slowly more dogmatic such that in the first century BCE Aenesidemus denounced the Academics as "Stoics fighting against Stoics", breaking with the Academy to revive Pyrrhonism.  Aenesidemus's best known contribution to skepticism was his now-lost book, Pyrrhonian Discourses, which is only known to us through Photius, Sextus Empiricus, and to a lesser extent Diogenes Laërtius.  The skeptical arguments most closely associated with Aenesidemus are the ten modes described above designed to induce epoche. 