If you are a skeptic–or tempted by skepticism–you might want to consider which varieties of skepticism appeal to you and why. Here is a list of types that differ in significant ways:

• Pyrrhonian skepticism (named after Pyrro of Elis, ca. 300 BCE, who founded the Skeptical School): A cultivated habit of refusing to believe or disbelieve all important matters, including skepticism itself. Its purpose is to accomplish mental peace by abandoning troubling questions and commitments. It advises the regular use of techniques that reduce our anxiety about the things we might believe or about not knowing what is true. For example, we can rehearse arguments on both sides of important questions to teach ourselves to suspend judgment.
• Academic skepticism (the position adopted by the Academy, which Plato founded, but roughly six centuries after his death): A method that employs the arguments invented by the Pyrrhonists to refute the views of other philosophical schools, without a goal of landing in permanent agnosticism or promoting mental health. The term “academic” is apt, because this kind of skepticism is more like a toolkit for specialists than a way of life.
• Cartesian skepticism (named after Rene Descartes, although practiced by others before and after him): A philosophical method that begins by doubting everything that is possible to doubt, especially deep and general beliefs, in order to identify any indubitable beliefs, which then become the foundations of a more secure philosophy. Here, the psychological goal is to accomplish certainty, not to escape from belief.
• Edmund Husserl’s epoche: A more radical form of Cartesian skepticism, in which the analyst drops all the categories and vocabulary developed in the history of philosophy and tries to describe experience itself without preconditions. Although Husserl’s motives seem academic, there are similarities with meditative techniques that aim to transcend various kinds of dualities; and Husserl admired the Buddhist Pali Canon. As with Cartesian skepticism, the goal is truth, not freedom from belief.
• Fallibilism: A belief that I could be wrong, which accompanies my other beliefs. This ancillary belief reminds me to check for errors, hedge against uncertainty, plan cautiously, and revisit assumptions. The psychological goal is more like permanent disquiet than calmness, although it may be possible to enjoy the constant pursuit of truth.
• Intellectual humility: If fallibilism is about beliefs, humility is about people. (At least, that is how the words ring for me.) It’s the attitude that people who disagree with me may be right and I may be wrong. Its consequences can include a genuine receptivity to other people’s claims, an investment in generous listening, and a tolerance for rival views. Humility can be uncomfortable if it means self-reproach; but if it means an appreciation for our fellow human beings, it can satisfying.
• Organized skepticism (one of the definitive features of science, according to Robert K. Merton): A set of procedures and practices that guide interactions among people who pursue truth together. Examples include double-blind peer-review or replicating other people’s experiments. Many of these techniques are supposed to be proof against the mental state of the scientist. Scientific methods do not attempt to make people humble in their hearts, but rather convert doubt into procedures.
• Liberalism as self-correction: This is a cluster of ideas about how to design institutions that begins with worries about our ability to understand, judge, and plan wisely and thus recommends constantly challenging and revising the status quo. Proponents differ in their enthusiasm for elections, adversarial trials, individual rights, debate and deliberation, and/or markets as mechanisms for self-correction. For myself, I prefer a mix of these tools, because then each can check the others.
• Specific distrust: This is belief that a given belief, person, group, or institution is probably wrong. It can be warranted, based on evidence–such as a record of lying or incompetence–or it can itself be mistaken. Unlike doubt about a belief, which is about content, distrust focuses on the source. If I say P, and you think not-P, that is a disagreement. But if you think, “I doubt that guy Peter Levine would be right about P,” that is distrust.
• Social distrust: This is a variable measured by social scientists, and one classic measure is a question about trusting other people that has been included on the General Social Survey for decades (see the graph below). Although the question is vague and does not distinguish among kinds of trust or categories of people, individuals’ responses predict many valuable outcomes. Thus the measure is conceptually vague yet empirically valid. Distrust is a character trait that can be affected by social circumstances.
• Institutional distrust: In contrast to a view that a specific institution should not be trusted, this is a general stance of skepticism about the influential institutions of a society, or at least a wide swath of them. It does not accept that institutions exhibit organized skepticism or liberal self-correction but takes them to be self-interested or even hostile. Like social distrust, this is a character trait that relates to social circumstances.

To put my own cards on the table: I admire fallibilism, humility, and institutionalized skepticism, in both science and politics. I accept that they can promote disquiet, but discomfort may be necessary for responsible action.

I also think there is a limited wisdom in Pyrrhonism. Although radical skepticism encourages passivity and removes motivations to care about other people, Pyrrhonist techniques for promoting doubt can counter anxiety and what Keats called an "irritable reaching after fact and reason." We need to know when to pursue truth and when to let it go. Furthermore, recognizing that there are matters beyond our ability to know or to capture in language is (for me) a source of comfort.

Specific distrust can be warranted, although we should strive to replace doubt about the source of a given claim with justified doubt about the claim itself. Disbelieving something because of who said it is an ad hominem argument, which is a logical fallacy. It is better to consider whether the claim is valid or not. The problem in the modern world is that no individual can assess most important beliefs, because they depend on countless people's previous contributions. To a large extent, we must trust or distrust the messenger, such as a teacher, physician, or engineer. And, in turn, that messenger learned from other specialists, who learned from others. The whole structure depends on trust.

Distrusting other people and institutions is understandable. The solution is not to hector people that they should trust more. Nevertheless, general distrust is harmful. It robs people of the advantages of modernity, such as the results of science.

An optimist might hope that by making institutions actually more fallibilist and self-correcting, we can encourage wider trust. However, in a world of propaganda and ideology--and deep inequality--such solutions may fail, and people may continue to distrust ideas that merit their belief.

One more version of skepticism is my favorite:

• Michel de Montaigne read the Skeptics, particularly a 1562 translation of Sextus. He remained an active participant in public life--indeed, much better respected as a statesman than a writer during his own lifetime. However, his moderate skepticism influenced his politics. "I am firmly attached to the sanest of the parties, but I do not desire to be particularly known as the enemy of the others beyond what is generally reasonable" (1145). "During the present confusion in this State of ours my own interest has not made me fail to recognize laudable qualities in our adversaries nor reprehensible ones among those whom I follow" (1114). He felt that he had generally done his civic duty (1115), yet he reserved most of his time for private reflection. And in that domain, he avoided trying to know what was true (or whether previous authors were right or wrong) but rather made a study of himself. "I would rather be an expert on myself than on Cicero" (1218). When he looked within, he found numerous inconsistencies and imperfections. Rather than making him dissatisfied or irritable, these explorations gave him some "peace of mind and happiness" (1153). His equanimity palpably improved between "To Study Philosophy is to Learn to Die" (before 1580) and "Of Experience" (ca. 1590).

---

I quote Montaigne from M.A. Screech's translation. See also: Foucault’s spiritual exercises; does skepticism promote a tranquil mind?; Montaigne and Buddhism; against the idea of viewpoint diversity; Cuttings version 2.0: a book about happiness; thinking both sides of the limits of human cognition