Lecture Notes: The Problem of Skepticism

Introduction to Skepticism

• Lecturer: Jennifer Nagel, Philosophy Professor, University of Toronto
• Focus: The problem of skepticism and human knowledge

Key Questions

• What do you know for sure?
  • Are you certain of watching a video on your computer?
  • Can you prove you're awake and not dreaming?

Ancient Skeptical Traditions

• Origin: Ancient Greece
• Two traditions:
  • Academic Skepticism
    • Sensory impressions are unreliable.
    • Example: Mistaking identities based on memory or dreams.
    • Conclusion: Knowledge of the world is impossible.
  • Peronian Skepticism
    • Continuous inquiry and doubt.
    • Suspend judgment on all conclusions.

Classic Skeptical Arguments

• Dreaming Argument
  • Experience could be a dream (Zhuangzi’s butterfly dream).

Descartes and Skepticism

• René Descartes’ contributions:
  • Questions even mathematical truths (e.g., 2+3=5).
  • Evil Genius Scenario:
    • An entity deceives all sensory and mental experiences.
    • Challenge: Prove you are not deceived.

Modern Skeptical Scenarios

• Brain in a Vat
  • A brain receiving simulated experiences from a computer.
  • Experiences indistinguishable from reality.
  • Challenge: Prove you are not a brain in a vat.

Skeptical Scenarios

• Global Skeptical Scenarios
  • Challenge knowledge of almost everything.
• Local Skepticism
  • Challenge specific knowledge (e.g., knowledge of the past or specific facts like time).

Examples of Local Skepticism

• Alice and the Clock
  • Glances at a clock showing 4:30.
  • Raises doubt by considering if the clock might be broken.

Implications of Skepticism

• Skepticism shows how easily doubt can be cast on human knowledge.
• Raises questions about the validity of things considered easily known.

Upcoming Topics

• Solutions to skepticism
• Defense of human knowledge
• Further videos will cover answers to the skeptic’s challenges.