---
title: "Philosophical skepticism"
chunk: 5/9
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"
---

Dissent – The uncertainty demonstrated by the differences of opinions among philosophers and people in general.
Progress ad infinitum – All proof rests on matters themselves in need of proof, and so on to infinity, i.e, the regress argument.
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 based on an unsupported assumption.
Circularity – The truth asserted involves a circularity of proofs.
According to Victor Brochard "the five tropes can be regarded as the most radical and most precise formulation of philosophical skepticism that has ever been given.  In a sense, they are still irresistible today."

==== Academic skepticism ====

Pyrrho's thinking subsequently influenced the Platonic Academy, arising first in the Academic skepticism of the Middle Academy under Arcesilaus (c. 315 – 241 BCE) and then the New Academy under Carneades (c. 213–129 BCE). Clitomachus, a student of Carneades, interpreted his teacher's philosophy as suggesting an account of knowledge based on truth-likeness. The Roman politician and philosopher, Cicero, was also an adherent of the skepticism of the New Academy, even though a return to a more dogmatic orientation of the school was already beginning to take place.

==== Augustine on skepticism ====

In 386 CE, Augustine published Contra Academicos (Against the Academic Skeptics), which argued against claims made by the Academic Skeptics (266–90 BCE) on the following grounds:

Objection from Error: Through logic, Augustine argues that philosophical skepticism does not lead to happiness like the Academic Skeptics claim. His arguments is summarized as:
A wise man lives according to reason, and thus is able to be happy.
One who is searching for knowledge but never finds it is in error.
Imperfection objection: People in error are not happy, because being in error is an imperfection, and people cannot be happy with an imperfection.
Conclusion: One who is still seeking knowledge cannot be happy.
Error of Non-Assent: Augustine's argument that suspending belief does not fully prevent one from error. His argument is summarized below.
Introduction of the error: Let P be true. If a person fails to believe P due to suspension of belief in order to avoid error, the person is also committing an error.
The Anecdote of the Two Travelers: Travelers A and B are trying to reach the same destination. At a fork in the road, a poor shepherd tells them to go left. Traveler A immediately believes him and reaches the correct destination. Traveler B suspends belief, and instead believes in the advice of a well-dressed townsman to go right, because his advice seems more persuasive. However, the townsman is actually a samardocus (con man) so Traveler B never reaches the correct destination.
The Anecdote of the Adulterer: A man suspends belief that adultery is bad, and commits adultery with another man's wife because it is persuasive to him. Under Academic Skepticism, this man cannot be charged because he acted on what was persuasive to him without assenting belief.
Conclusion: Suspending belief exposes individuals to an error as defined by the Academic Skeptics.

=== Skepticism's revival in the sixteenth century ===
Francisco Sanches's That Nothing is Known (published in 1581 as Quod nihil scitur) is one of the crucial texts of Renaissance skepticism.

==== Michel de Montaigne (1533–1592) ====

The most notable figure of the Skepticism revival in the 1500s, Michel de Montaigne wrote about his studies of Academic Skepticism and Pyrrhonism through his Essais.
His most notable writings on skepticism occurred in an essay written mostly in 1575–1576, "Apologie de Raimond Sebond", when he was reading Sextus Empiricus and trying to translate Raimond Sebond's writing, including his proof of Christianity's natural existence. The reception to Montaigne's translations included some criticisms of Sebond's proof. Montaigne responded to some of them in Apologie, including a defense for Sebond's logic that is skeptical in nature and similar to Pyrrhonism. His refutation is as follows:

Critics claiming Sebond's arguments are weak show how egoistic humans believe that their logic is superior to others'.
Many animals can be observed to be superior to humans in certain respects. To argue this point, Montaigne even writes about dogs who are logical and creates their own syllogisms to understand the world around them. This was an example used in Sextus Empiricus.
Since animals also have rationality, the over-glorification of man's mental capabilities is a trap—man's folly. One man's reason cannot be assuredly better than another's as a result.
Ignorance is even recommended by religion so that an individual can reach faith through obediently following divine instructions to learn, not by one's logic.

==== Marin Mersenne (1588–1648) ====

Marin Mersenne was an author, mathematician, scientist, and philosopher. He wrote in defense of science and Christianity against atheists and Pyrrhonists before retiring to encourage development of science and the "new philosophy", which includes philosophers like Gassendi, Descartes, Galileo, and Hobbes. A major work of his in relation to Skepticism is La Verité des Sciences, in which he argues that although we may not be able to know the true nature of things, we can still formulate certain laws and rules for sense-perceptions through science.
Additionally, he points out that we do not doubt everything because: