Overview

How do you know that “All bachelors are unmarried”? You don’t need to interview every bachelor. You just know it by the definition of the words. That’s a priori.

Core Idea

Analytic vs. Synthetic:

  • Analytic: True by definition (“Triangles have 3 sides”).
  • Synthetic: True by experience (“The cat is on the mat”). Kant asked: Is there “Synthetic A Priori” knowledge? (Knowledge about the world that we know without looking?).

Formal Definition (if applicable)

Necessary Truth: A statement that must be true in all possible worlds ($2+2=4$). Contingent Truth: A statement that happens to be true but could have been false (The sky is blue).

Intuition

  • A Priori: From the armchair. (Math, Logic).
  • A Posteriori: From the lab. (Physics, Biology).

Examples

  • “Something cannot be both red and green all over at the same time.” (A priori).
  • “Water boils at 100°C.” (A posteriori—we had to measure it).
  • “I think, therefore I am.” (A priori).

Common Misconceptions

  • “A priori means ‘before’.” (It means independent of experience, not necessarily chronologically before.)
  • “It’s innate.” (You might need to learn the language first, but the justification doesn’t depend on experience.)
  • Rationalism: The view that reason is the chief source of knowledge (Descartes, Spinoza, Leibniz).
  • Empiricism: The view that experience is the chief source (Locke, Berkeley, Hume).
  • Innate Ideas: Concepts we are born with (God? Geometry?).

Applications

  • Mathematics: Purely a priori.
  • Ethics: Are moral truths a priori? (e.g., “Torture is wrong”).
  • Metaphysics: Trying to figure out the structure of reality using only reason.

Criticism / Limitations

Quine argued that the analytic/synthetic distinction is blurry. Maybe even math is just very well-confirmed empirical knowledge.

Further Reading

  • Kant, Critique of Pure Reason
  • Kripke, Naming and Necessity