Philosophical Skepticism: Can We Have Knowledge?

Introduction to Philosophical Skepticism

• Concept: Philosophical skepticism questions whether we can truly have knowledge.
• Scenarios:
  • Deception by an evil demon.
  • Being in a simulation (e.g., The Matrix) or a brain in a jar scenario.
  • These scenarios suggest we might be unable to distinguish between true knowledge and deception.

Difference Between Ordinary and Philosophical Doubt

• Ordinary Doubt:
  • Everyday uncertainties (e.g., did I turn off the lights?).
  • Can be resolved with evidence (e.g., checking a calendar).
• Philosophical Doubt:
  • Extends beyond ordinary evidence.
  • Example thought experiment: Being a brain in a jar.
  • Hard to resolve as it questions the very foundation of perception.

Famous Skeptical Scenarios

• The Matrix: Artificial stimuli creating perceptions of a false reality.
• Simulation Hypothesis: Future technology creating simulations indistinguishable from reality.
• Purpose: These scenarios highlight the difficulty in justifying beliefs when deception is indistinguishable from reality.

Global Skepticism vs. Non-Skepticism

• Global Skeptic: Claims we cannot know anything due to plausible skeptical scenarios.
• Non-Skeptic: Defends the possibility of ordinary knowledge despite skepticism.

Descartes' Waves of Doubt

• First Wave: Illusion
  • Sensory illusions can mislead (e.g., a stick in water appears bent).
  • Does not lead to total skepticism.
• Second Wave: Dreaming
  • Dreams can mimic reality, leading to doubt about wakeful experiences.
• Third Wave: Evil Demon Hypothesis
  • A powerful deceiver could manipulate all perceptions.
  • Undermines even basic knowledge (e.g., math).

Descartes' Response to Skepticism

• Cogito Argument: "I think, therefore I am."
  • Even if deceived, the act of doubting confirms the doubter's existence.
• Existence of God
  • Descartes argues for a non-deceptive God to validate perceptions and knowledge.
  • Claims God's existence justifies trust in perception.

Responses to Skepticism

• Infallibilism
  • Knowledge must be impossible to doubt.
  • Critiqued for being too strict and easily challenged by skeptics.
• Coherence and Consistency
  • Senses corroborate each other (e.g., seeing and hearing the same thing).
  • Best hypothesis is that perceptions reflect reality.
• Barkley's Idealism
  • Perception is reality; skepticism about perception doesn't apply.

Alternative Definitions of Knowledge

• Reliabilism
  • Knowledge as true belief formed by reliable processes rather than justification.
  • Conditional on not being in a skeptical scenario.

Conclusion

• Skepticism poses significant challenges to defining knowledge.
• Responses vary from traditional defenses to alternative theories.
• Debate on skepticism remains active, touching on foundational philosophical questions.