A Comprehensive Introduction to Philosophical Skepticism

General Overview and Basic Definitions of Skepticism

  • Skepticism is and umbrella term that encompasses numerous different philosophical views.

  • The first fundamental distinction to draw when considering skepticism is between object or domain-specific skepticism versus radical skepticism.

  • Radical skepticism is further divided into categories such as generalized empirical skepticism or global skepticism.

  • The goal of studying skepticism is to provide a basic background and survey skeptical challenges to knowledge across different philosophical traditions.

Domain-Specific Skepticism

  • Domain-specific skepticism involves withholding belief from something that is widely accepted among a specific group or society.

  • It often targets the existence of certain objects or specific theories that others accept.

  • Common examples of domain-specific skepticism include:     * Skepticism regarding climate science (e.g., whether human activity causes global warming).     * Skepticism regarding the evolutionary theory of biology.     * Skepticism regarding the existence of supernatural entities.     * Skepticism regarding the existence of God.     * Skepticism regarding the dominant theories surrounding the events of 9/11.

Radical Skepticism: Generalized Empirical and Global Variations

  • Radical skepticism consists of two primary forms:

  • Generalized Empirical Skepticism:     * The claim that humans cannot acquire knowledge through sense experiences of the world.     * Some proponents of this view still believe we can acquire substantial knowledge through other means, such as reason, to develop a wise point of view.     * This is often linked to Rationalism, a philosophical perspective holding that humans primarily know the world through reason rather than the senses.

  • Global Skepticism:     * The view that humans have no knowledge of anything whatsoever.     * This applies to every possible domain of inquiry, including but not limited to:         * Mathematics         * Philosophy         * History         * Sociology         * Neuroscience         * Physics     * Motivations for global skepticism include hypothetical scenarios or thought experiments such as:         * The Matrix (simulated reality).         * Inception (layers of dreaming).         * Brains in a vat (external neural stimulation).         * The possibility that humans are biologically "wired" to get things wrong.         * The nature of dreams and their indistinguishability from reality.

Skeptical Challenges in Chinese Taoist Philosophy

  • A famous skeptical challenge comes from the Chinese philosopher Chuang Tzu and his "butterfly dream" story.

  • The Narrative:     * Chuang Tzu once dreamt he was a butterfly, fluttering about and conscious only of his happiness as a butterfly, unaware of his identity as Chuang Tzu.     * Upon awakening, he found himself to be Chuang Tzu again.     * The Philosophical Puzzle: He realized he did not know whether he was a man dreaming he was a butterfly, or a butterfly now dreaming he is a man.

  • Metempsychosis: Chuang Tzu notes that while there is necessarily a barrier between a man and a butterfly, the transition between states is referred to as metempsychosis.

  • Epistemological Implication: If one cannot rule out the possibility of dreaming in any given experience, and dreams produce mistaken beliefs about surroundings, it becomes unclear how one can claim to have certain knowledge.

Pre-Socratic Greek Philosophy and Skepticism of the Senses

  • Skeptical challenges in Europe emerged in Greece during the "pre-Socratic" period, prior to the writings of Socrates and Plato.

  • Heraclitus:     * His skeptical concerns were based on the observation that the world is in a state of constant flux.     * Famous Dictum: "You can't step into the same river twice."     * Epistemological View: Knowledge is impossible because there is no stable subject to be known. Since nothing stays the same, once something is "grasped" by the mind, it has already changed and is no longer what it was.

  • Parmenides:     * Parmenides was one of the first Rationalists. He argued that knowledge is acquired only through reasoning and thinking, not through sense experience.     * He believed reality must contain a "continuing substance" because only that which is unchanging is real.     * He agreed with Heraclitus that the world appears to be in constant change, which would normally undercut knowledge.     * However, he concluded that because we do have knowledge, the appearance of change must be a deceptive illusion.

  • Zeno of Elea:     * A student of Parmenides who advocated that knowledge from the senses was impossible.     * He is famous for "Zeno's Paradoxes," which philosophers continue to address.

Parmenides’ Argument Against the Senses

  • Parmenides’ logical defense for the unreality of change (and the resulting unreliability of the senses) follows this structure:     1. If something changes, it must have property XX and also not have property XX (Premise).     2. Having property XX and not having property XX simultaneously is a logical contradiction (Law of Non-Contradiction).     3. Nothing can be real if it violates the laws of logic.     4. Therefore, change is unreal.     5. If change is unreal, our senses (which perceive change) deceive us.     6. If our senses deceive us, they do not provide us knowledge.     7. Conclusion: Our senses do not provide us knowledge.

Cartesian Skepticism and the Wax Argument

  • Rene Descartes used the example of a piece of wax in his Meditations on First Philosophy to argue for Rationalism.

  • Sense Observation of Wax:     * At room temperature: The wax is hard, makes a sound when knocked, and has a weak aroma.     * When heated: The wax becomes liquid, makes no sound, and has a very strong aroma.

  • The Rationalist Conclusion:     * Despite the senses reporting completely different properties (liquid vs. solid, quiet vs. noisy), we still know it is the same piece of wax.     * Nothing from our raw senses could tell us it is the same substance in both cases.     * Therefore, we must know the identity of the wax through reason alone, not through the shifting data of the senses.

Descartes' Method of Doubt and Hyperbolic Doubt

  • Descartes was not a global skeptic; he used skeptical arguments as a tool to refute them and establish a firm foundation for knowledge.

  • Method of Doubt (Hyperbolic Doubt):     * Descartes adopted the standard that anything that can be doubted cannot count as knowledge.     * He argued we cannot claim to know a proposition pp if its truth can be subjected to even the slightest doubt.     * Descartes stated: "I ought no less carefully to withhold my assent from matters which are not entirely certain and indubitable than from those which appear to me manifestly to be false."     * In this view, being uncertain of a truth is structurally equivalent to believing something false in terms of justification.

  • Social/Legal Analogy: This high standard for certainty is reflected in courts of law, where a judge or jury must decide "not guilty" if there is any "reasonable doubt."

Descartes’ Two Major Arguments for Global Skepticism

  • Descartes used two primary arguments to motivate radical doubt:

  • The Dream Argument:     * We cannot distinguish with absolute certainty whether we are currently dreaming or awake.     * If we are dreaming, we do not have knowledge of our immediate physical surroundings.     * Example: A person might believe they are seeing a PowerPoint slide in a classroom, but if they are dreaming, that slide does not exist and the belief is false.

  • The Evil Genius (Evil Demon) Argument:     * Descartes posits the possibility of an all-powerful but malicious being (an evil genius/demon) who systematically deceives us.     * This demon could make us believe in a non-existent earth, heaven, or physical bodies.     * This possibility allows one to doubt any belief, including mathematical claims, sense-based claims, or ethics.

  • Standardized Evil Genius Argument:     1. We cannot be certain that our beliefs are not caused by an evil genius.     2. If we cannot be certain our beliefs are not caused by an evil genius, we cannot be certain our beliefs are real.     3. If we cannot be certain our beliefs are real, we are not justified in holding them.     4. If we are not justified in holding beliefs, we do not have knowledge.     5. Therefore, we do not have knowledge.

G.E. Moore’s Common-Sense Refutation

  • Oxford philosopher G.E. Moore (1873-1958) attempted to undercut the dream argument with his "Two Hands Argument."

  • Moore's Proof:     1. Here is one hand (gesturing).     2. Here is another (gesturing).     3. Therefore, external objects exist.

  • Criteria for a Rigorous Proof: Moore claimed his proof was successful because:     1. The premises are different from the conclusion (non-circular).     2. The conclusion follows logically from the premises.     3. The premises are known to be true (e.g., he is not blind and is looking directly at his hands).

  • Defense of the Refutation:     * Moore argued it is more plausible to accept that he has two hands than to accept the skeptic's premise that we cannot be sure we aren't dreaming.     * He claimed waking experiences fit together in a coherent stream that dreaming experiences do not.     * Moore's main takeaway is that "knowing" does not always require a rigorous proof, even though it can serve as a premise in one.

Questions and Discussion

  • Reflection Question: What are the implications of radical skeptical concerns regarding the senses? Do these questions raise important concerns for human claims to knowledge, or are they somehow misguided?

  • Instruction: Students are encouraged to develop a cogent argument for their own views on these challenges.