IN THIS LESSON

When a society tears itself apart over beliefs it cannot justify, philosophy steps in to ask what it really means to know anything at all.

Topics discussed:

  • The 16th and 17th centuries were marked by intense religious fanaticism and violence (e.g., the Peasant Rebellion, Münster, the Thirty Years’ War).

  • These events pushed thinkers to demand firmer foundations for belief—not mere authority or dogma.

  • But agreement proved impossible: philosophers disagreed sharply about what counts as justification and what a belief must rest on to be considered rational.

  • Meanwhile, ancient texts and ideas—especially from Plato and the skeptics—were being rediscovered, raising old questions in a new era.

  • The lesson introduces epistemology, the study of knowledge, and frames the central issue: What makes a belief justified?

  • Plato’s Justified True Belief (JTB) theory sets the stage, but Agrippa’s Regress Argument challenges whether justification is possible at all (the setup for the next steps in the course).

  • Pyrrhonian skepticism reappears as a powerful alternative: suspend judgment to achieve ataraxia, tranquility free from dogmatic conflict.

Focus Questions

  • Why did the religious violence of the 16th–17th centuries create a demand for better standards of justification?

  • How does the Justified True Belief (JTB) model attempt to explain what knowledge is?

  • What problem does Agrippa’s Regress Argument raise for the very possibility of justified belief?

  • Why might rediscovered ancient ideas (e.g., Plato, Pyrrhonists) feel newly relevant to thinkers living through intellectual crisis?

  • Why do Pyrrhonian skeptics claim beliefs disturb us and that tranquility comes from suspending judgment?

Glossary

The Search for Certainty

  • Epistemology: The branch of philosophy concerned with the nature and limits of knowledge. It asks: "What is truth?" and "What is the right method for acquiring true beliefs?"

  • Historical Catalyst: 16th and 17th-century religious violence (e.g., The Thirty Years' War) led thinkers to seek rational foundations for belief rather than relying solely on faith or dogma.

  • Rational Foundations: The idea that our beliefs must rest on firm, logical grounds to avoid the bloodshed caused by blind fanaticism.

Defining Knowledge: The JTB Theory

  • The JTB Theory of Knowledge: A definition of knowledge derived from Plato's Theaetetus.

    • Justified: You must have good reasons for the belief.

    • True: The belief must correspond to reality.

    • Belief: You must actually accept that the statement is the case.

  • Necessary Conditions: For a subject (S) to know a proposition (P), all three conditions must be met. If P is false, or if S doesn't believe it, or if S has no justification (no good reason or reasons for believing it), it is not knowledge.

The Skeptic’s Challenge

  • Pyrrhonism: A form of radical skepticism founded by Pyrrho of Elis. It suggests that beliefs are obstacles to ataraxia (undisturbedness/inner peace).

    • Ataraxia (ἀταραξία): A state of "undisturbedness," mental calmness, or inner peace. In Pyrrhonism, this is the ultimate goal of philosophy; it is achieved when we stop the mental struggle of trying to decide which of our conflicting impressions is "true".

    • Epoché (ἐποχή): The act of "suspending judgment." This is the core practice of the Pyrrhonian skeptic. When faced with two equally convincing but contradictory arguments, the skeptic does not choose a side; instead, they "check out" of the debate entirely, which leads to ataraxia.

    • Assent: The mental act of "saying yes" to an impression or accepting a thought as true . The skeptic believes that we cause ourselves unnecessary distress by habitually granting assent to things that are not actually certain.

    • Impressions: The way things "seem" to us through our senses or thoughts (e.g., "the honey seems sweet"). The skeptic accepts the impression but withholds judgment on whether the honey actually is sweet in its fundamental nature.

  • The Regress Argument: An argument claiming that knowledge is impossible because:

    1. Justification requires good reasons.

    2. Good reasons are themselves justified beliefs.

    3. Therefore, you would need an infinite amount of reasons, which is humanly impossible.

  • Agrippa’s Trilemma: The claim that all attempts at justification fall into one of three failing traps:

    1. Infinite Regress: A chain of reasons that never ends.

    2. Dogma: Claiming something is true without needing a reason (which is unjustified)

    3. Circularity: Assuming what you are trying to prove.

For other questions…

ALEX 1.2:
The Diagnostician

Instructions to the Learner

As mentioned in the lesson, the JTB theory has been immensely influential. As far back as Plato, epistemic philosophers have been pointing out that one cannot arrive at justified true belief on accident. For example, one cannot achieve knowledge of the time by looking at a clock that is broken but just happens to be stuck at the exact time that you look at it(!). Knowledge, in other words, has to be non-lucky.

In this activity, you will work with an AI tutor to diagnose whether a person in a given scenario knows something, according to the classical JTB model.

Your goals are to:

  1. Practice identifying the truth, belief, and justification components in real-life examples.

  2. Explain why each component is or is not present.

  3. Strengthen your ability to apply the JTB framework to messy everyday situations.

  4. Receive targeted feedback on your reasoning so you can refine it — this is deliberate practice.

Here’s what will happen:

  • The AI will present you with a series of short belief scenarios (five total).

  • For each one, you will explain whether the person:

    • (1) has a belief

    • (2) the belief is true

    • (3) the belief is justified

    • (4) therefore knows (or does not know) the proposition

  • The AI will push back on your reasoning, point out inconsistencies, and ask follow-up questions.

  • After feedback, you will refine your diagnosis.

When you’re ready, copy the AI Prompt below and paste it into your AI chat.

After you finish, return to Canvas and submit your transcript + reflection.

AI Prompt


You are playing the role of a tutor, helping a student master the learning objective:
“Apply the Justified True Belief (JTB) framework to real cases and explain why a belief does or does not count as knowledge.”

Your job is to create and guide a structured activity called The Diagnostician. The activity proceeds as follows:

Present the student with a belief scenario. The scenario should be short (3–5 sentences) and about an everyday situation. The proposition at issue must actually be true in the scenario, even if the agent does not know this.

After presenting the scenario, ask the student to answer the following questions:
a. Does the person believe the proposition? Why or why not?
b. Is the proposition true?
c. Is the person justified in believing it? Why or why not?
d. Does the person know? Explain using the JTB model.

After the student answers, evaluate their reasoning.

Identify what they got right.

Challenge any unclear or incomplete reasoning.

Ask at least one follow-up question to deepen their understanding.

Require them to refine or revise their answer.

Continue this process for five scenarios, gradually increasing difficulty.

Begin with simple “lucky guess” or “weak justification” cases.

Move to cases involving conflicting evidence, misleading evidence, or accidental truths.

Ensure each case allows analysis using JTB concepts.

After all five scenarios, ask the student for a final reflection:
“What have you learned about the difference between true belief and knowledge? Which component of JTB do you find hardest to evaluate, and why?”

Keep the tone encouraging, patient, and Socratic.
Your goal is to help the student internalize how JTB works by actively applying it to real examples and revising their reasoning through deliberate practice.
    

More to Explore

The activities below are optional. Do them if you want more practice, deeper self-reflection, or you just like arguing with machines.

The
Death of Socrates

As I mentioned in the lesson, the painting The Death of Socrates, by Jacques-Louis David, has some hidden layers of depth. Check out this video to learn about that.

To learn more about Pyrrho, check out…
L111.2.6: Scythian Shadows

Reading List

Julia Annas & Jonathan Barnes, The Modes of Scepticism.

Gordon Barnes, Applied Epistemology: An Introduction.

Roderick Beaton, The Greeks: A Global History.

Christopher Beckwith, Greek Buddha.

Richard DeWitt, Worldviews: An Introduction to the History and Philosophy of Science.

Lorraine Daston & Katharine Park, Wonders and the Order of Nature.

John Greco (Ed.), The Oxford Handbook of Skepticism

Thomas Kuhn, The Structure of Scientific Revolutions.

Michael Shenefelt & Heidi White, If A, Then B: How the World Discovered Logic