Critical Thinking: Deductive Forms, Milgram & Zimbardo, Cognitive Development, and Skepticism

Modus ponens

  • Form: two premises then the conclusion

  • Structure (logic): (A \rightarrow B), A \vdash B

  • Explanation: From a conditional $A \rightarrow B$ and the antecedent $A$, infer the consequent $B$

  • Key terms: antecedent = $A$, consequent = $B$

Modus tollens

  • Form: from a conditional and the negation of the consequent, infer the negation of the antecedent

  • Structure: (A \rightarrow B), \neg B \vdash \neg A

  • Explanation: If $A \rightarrow B$ and $\neg B$, then $\neg A$

Chain argument (hypothetical syllogism)

  • Form: from $A \rightarrow B$ and $B \rightarrow C$, infer $A \rightarrow C$

  • Structure: (A \rightarrow B), (B \rightarrow C) \vdash (A \rightarrow C)

  • Notes: also considered a hypothetical syllogism; connects a sequence of conditionals

Disjunctive syllogism (argument from elimination)

  • Form: from $A \lor B$ and $\neg A$, infer $B$

  • Structure: (A \lor B), \neg A \vdash B

Milgram experiment (1960–1963)

  • Purpose: test obedience to authority and willingness to harm others under instruction

  • Location/lead: Yale University; Stanley Milgram

  • Design: participants as teachers; learners as confederates; shocks supposedly for memory tasks; draws manipulated to create belief of 50/50 roles

  • Procedure: shocks increased with wrong answers up to 450 volts; shocks not real

  • Result: 65\% delivered up to 450 volts; 35\% refused before max

  • Lesson: ordinary people may follow authority to commit harm; critical thinking helps resist

  • Ethical note: not permissible by today’s standards; time capsules for understanding authority dynamics

Zimbardo Stanford Prison Experiment (1971)

  • Purpose: examine power dynamics in a simulated prison

  • Location/lead: Stanford University; Philip Zimbardo

  • Design: volunteers randomly assigned as guards or prisoners; mock prison in basement; uniforms to depersonalize

  • Outcome: escalation of abusive, dehumanizing behavior; some prisoners experienced severe distress

  • Duration: intended two weeks but halted after 6 days

  • Lesson: authority and role conformity can drive cruel behavior; need for oversight and ethical safeguards

  • takeaway: good critical thinking helps resist abusive roles and authority when warranted

Cognitive development (William Perry, Jr.)

  • Concept: lifelong process of acquiring intelligent/reflective thinking

  • Three stages/phases:

    • Dualism: truth is black-and-white; authority figures know the truth; passively defer to them

    • Relativism: truth is relative; all opinions have equal standing; risk of paralysis from excessive skepticism

    • Commitment: combine reason with evidence to form one's own well-supported beliefs; open to revision with new evidence

  • Key idea: progression moves from reliance on authorities to independent, evidence-based judgment

Qualities of a good critical thinker

  • Analytical skills: provide logical support for beliefs; avoid unfounded opinions

  • Effective communication: clear speaking/writing; strong listening; adapt to audience and style

  • Research/inquiry skills: gather/evaluate evidence; distinguish reliable sources; synthesize information

  • Flexibility: willing to change minds/plans when warranted; remain open to alternatives

  • Open-minded skepticism: balance skepticism with openness; require good evidence; avoid prejudgment

Open-minded skepticism & Descartes (method of doubt)

  • Open-minded skepticism: evaluate evidence before belief; avoid credulity; remain willing to revise

  • Method of doubt (Descartes): seek certainty by doubting anything that can be doubted

  • Core idea: doubt as a systematic tool to reach secure beliefs; provisional conviction only when indubitable

  • Famous outcome: cogito — \text{Cogito ergo sum} (I think, therefore I am)

  • Context: 17th century age of reason; Descartes sought a solid foundation for knowledge

  • Practical takeaway: maintain healthy doubt while demanding evidence before belief

Descartes: cogito in plain terms

  • Even if external reality were doubtful, thinking is occurring, so the thinker’s existence is confirmed

  • Therefore, at minimum, consciousness exists as a thinking thing