1. What is Evidence?
The reason why we think an idea/statement/etc. makes logical sense.
Something that is used to demonstrate truth.
An outward sign that furnishes proof.

2. How do we use evidence in Critical Thinking?
Resist the idea of “lazy thinking”
Check the quality/quantity of evidence
Review evidence BEFORE expressing an opinion

3. Types of Evidence Anecdotal Testimonial Statistical Analogical
Use of your own/someone’s experience to prove a point
Testimonial
Use of another person’s credibility to prove a point
Statistical
Use of numbers/data to prove a point
Analogical
Use of similar situations to prove a point

4. Anecdotal Evidence
Personal Experience
Unpublished Report (Gossip)

5. Testimonial Evidence Eyewitness Report Celebrity Testimony
Expert Opinion
Formal Observation (detached vs. participant)

6. Statistical Evidence Published Report Experiment Statistics Survey
Research Review

7. What is “sufficient” evidence?
“Evidence is sufficient when it permits a judgment to be made with certainty.”
“If certainty is unattainable, evidence is sufficient if one view of the issue has been shown to have the force of probability.”
“In all other cases, the evidence must be considered insufficient.”

8. Time to form an Opinion!
Work in your groups and write a one-paragraph opinion (with support) on each of the following:
Should the State of Arizona allow miners to dig for uranium in the Grand Canyon?
Should illegal immigrants be allowed to have Arizona driver’s licenses?
Should smokers have to pay more for health insurance than non-smokers?

9. Did you back up your opinion?
What kind of evidence did you seek out to prove your opinion and reasoning?
What kinds of questions did you ask when critically reading each type of evidence?
Did you use credible sources?
How did your group come to consensus on your opinion? Do you feel that it made your opinion statement weaker?