Evidence

Goals

1. Describe evidence.
2. Skillfully use evidence to make claims and evaluate claims.

Evidence (What)

Evidence refers to information that can be independently verified by multiple people—such as observations, measurements, calculations, or other reproducible results—used to support a claim.

Analysis (Main Ideas)

• The information must be verifiable (checkable).
• Multiple people must be able to verify it independently.
• The information must be relevant to supporting a claim.

Examples

• Concrete samples are tested to determine average breaking strength.
• DNA analysis shows that a person was present at a crime scene.
• Five people at a meeting independently confirm a colleague’s statement.
• A mathematical calculation is used to predict the performance of an engine.
• Polling data from a representative sample is used to forecast an election outcome.

What Is Not Evidence?

Not all information that people use to support claims qualifies as evidence.

Examples of What Is Not Evidence

• Anecdotes – “My uncle smoked his whole life and never got sick.”
• Beliefs – “I just know it’s true.”
• Hearsay – “I heard someone say that…”
• Popularity - “Everyone thinks this is true”
• Unverifiable claims – “Aliens cured my illness.”
• Biased sources without corroboration – A blog post making extraordinary claims with no supporting data.
• Doctored or AI-generated images – Content that can’t be traced to a verifiable source.

Key Distinction

What separates evidence from non-evidence is verifiability, reproducibility, and relevance. If it can’t be checked by others or tested through reliable methods, it’s not evidence—even if it sounds persuasive.

Rationale

Skill with evidence is essential for several reasons:

1. Foundation of Truth – Facts are established through the use of evidence and sound reasoning.

2. Basis for Justice – Legal systems rely on evidence to determine guilt or innocence.

3. Judging Quality – Not all evidence is reliable. Measurements can be faulty, memories can be inaccurate, and calculations can be flawed. Skill with evidence helps a person evaluate its quality.

4. Defense Against Manipulation – Even true evidence can be used selectively or misleadingly by unethical persuaders. Knowing how to assess evidence protects you from being misled.

Skilled Use of Evidence

To use evidence skillfully, aim to discover the truth—not just to confirm a belief.

• Seek balance – Examine evidence both for and against the claim.
• Assess quality – Judge the strength of evidence using clear criteria (see “Good vs Bad Evidence”).
• Stay open – Be willing to change your mind based on stronger or better evidence.
• Communicate humbly – Use language that reflects uncertainty and openness.
  Example: “The evidence suggests that…” rather than “This proves that…”
• Accurate Measurement – Ensure that measurements are taken using appropriate tools, proven methods, and by individuals with the necessary skills and training.

Good Evidence versus Bad Evidence

Evidence varies in quality along a spectrum from bad to good. The quality depends on factors such as source credibility, methodology, and consistency with other information.

Good Evidence

Definition: Good evidence is information that is likely to be true or reliable due to its credible source, sound methodology, and alignment with other verified data.

Indicators of Good Evidence:

1. Reliable – Comes from credible, unbiased, and expert sources.
2. Relevant – Directly supports the specific claim or argument.
3. Consistent – Matches other established evidence without contradiction.
4. Comprehensive – Addresses the topic fully, including alternative perspectives.
5. Methodologically Sound – Collected and analyzed using rigorous, widely accepted standards.

Bad Evidence

Definition: Bad evidence is information that is unlikely to be true or reliable due to poor sourcing, flawed methodology, or inconsistency with other credible data.

Indicators of Bad Evidence:

1. Unreliable – Originates from biased, non-expert, or disreputable sources.
2. Irrelevant – Does not directly relate to the claim being evaluated.
3. Inconsistent – Conflicts with other credible evidence or contains contradictions.
4. Incomplete – Presents a narrow, selective, or one-sided view.
5. Methodologically Flawed – Based on sloppy, biased, or unaccepted research practices.