Overview

Evidence is the information or data that supports a belief or proposition. In epistemology, it is the currency of justification. The central question is: What constitutes evidence, and how does it justify belief?

Core Idea

The core idea is that beliefs should be proportioned to the evidence (Evidentialism). If you have good evidence, you are justified; if not, you aren’t.

Formal Definition

Evidence is that which confers justification on a belief. It is often characterized as:

  1. Propositional: Evidence consists of facts or propositions.
  2. Mentalist: Evidence consists of mental states (experiences).
  3. Probabilistic: Evidence E supports hypothesis H if E makes H more probable.

Intuition

  • The Detective: A fingerprint on the gun is evidence that the suspect held the gun. It raises the probability of guilt.
  • The Scientist: Data from the telescope is evidence for the theory of black holes.

Examples

  • Sensory Evidence: Seeing rain is evidence that it is raining.
  • Testimonial Evidence: A witness saying “I saw him” is evidence.
  • Circumstantial Evidence: Indirect evidence (e.g., motive and opportunity) that implies a fact.

Common Misconceptions

  • Misconception: Evidence means “proof.”
    • Correction: Evidence comes in degrees. You can have weak evidence (a rumor) or strong evidence (DNA). Proof is the highest standard, usually reserved for math.
  • Misconception: Evidence speaks for itself.
    • Correction: Evidence always requires interpretation within a framework.
  • Evidentialism: The view that justification depends entirely on evidence.
  • Bayesianism: A mathematical framework for updating beliefs based on new evidence.
  • Underdetermination: The idea that evidence can support multiple rival theories equally well.

Applications

  • Law: The rules of evidence determine what can be presented in court.
  • Medicine: Evidence-Based Medicine (EBM) prioritizes clinical research over anecdote or tradition.

Criticism and Limitations

  • The Regress: If evidence justifies belief, what justifies the evidence? (Leads to Foundationalism vs. Coherentism).
  • Theory-Ladenness: Observation is often influenced by the theory we hold (we see what we expect to see), complicating the neutrality of evidence.

Further Reading

  • Evidence by Thomas Kelly
  • Evidentialism by Conee and Feldman
  • Knowledge and its Limits by Timothy Williamson (argues E=K, evidence is knowledge)