LOGIC AND CRITICAL THINKING

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LOGIC AND CRITICAL THINKING

• The Way to the Good Reasoning and Making Good
  Argument

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What Is Critical Thinking?

• Think it twice Dont take things for granted so
  easily.
• Always ask the why-question Try to find out the
  reason (the premises) why certain claim (the
  conclusion) can be supported.
• Examine and evaluate the relationship between the
  reasons and the claim.

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Paradoxes

• Self-defeating paradox The concept of all
  powerful God
• Zenos paradox An apparently unacceptable
  conclusion derived by apparently acceptable
  reasoning from apparently acceptable premises
• Semantic paradox The liars paradox
• The lawyers paradox
• Prisoners dilemma
• Russells paradox (Barbers paradox)
• The lottery paradox

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What is logic?

• Logic is not an empirical science
• Formal or informal science
• Logic v.s.Psychology
• 1. The Laws of Thinking
• 2. The Science of Reasoning
• 3. The Science of Argument
• The study of the methods and principles used to
  distinguish good (correct) from bad (incorrect)
  reasoning or argument.
• The way to the good reasoning (making good
  argument) and critical thinking

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What Is an Argument?

• An argument is the fundamental structure of the
  reasoning.
• An argument consists of premises and conclusion.
• An argument is used to provide reasons for
  supporting some claim or proposal.
• Logic aims to the study of the various forms of
  argument.
• The ultimate goal of logic is to evaluate
  arguments.

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The Standard Form of Argument

• P premise, C conclusion
• There must be some kind of supporting
  relationship between premises and conclusion.
• P1
• P2
• ?
• ?
• Pn (n?1)
• C

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Two Kinds of Argument

• The traditional but mistaken distinction between
  deduction and induction
• Deduction
  Induction
• Some general principles Some particular
  cases
• ? ?
• A particular case A general principle

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Deductive Argument

• Deductive argument is the argument that the
  premises necessarily support the conclusion.
• P1
• P2
• ?
• ?
• Pn
• C

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Inductive Argument

• Inductive argument is the argument that the
  premises probably support the conclusion.
• P1
• P2
• ?
• ?
• Pn
• C

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Evaluating An Argument

• There are two ways of evaluating an argument.
• Formal logic is to use the deductive criterion
  for evaluating arguments.
• Informal logic is to use the inductive criterion
  for evaluating argument.

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The Criterion for Evaluating a Deductive Argument

• Deductive Argument
• Valid Arg. Invalid Arg.
• Sound Arg. Unsound Arg. Unsound Arg.
• Good Arg. Bad Arg Bad Arg.

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The Criterion for Evaluating an Inductive Argument

• Inductive Argument
• Strong Arg. Weak Arg.
• Cogent Arg. Uncogent Arg.
  Uncogent Arg.
• 
  
• Good Arg. Bad Arg. Bad Arg.

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What Is a Good Argument

• 
  

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The Deductive Systems

• The truth table methods for evaluating deductive
  arguments
• The formal system of natural deduction
• 1. Propositional logic
• 2. Predicate logic
• The Aristotelian logic (Categorical Syllogism)
• The axiomatic system

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The Inductive Systems

• The methods of analogy and the probable inference
• Legal reasoning
• Mills method and causality
• Statistical reasoning and probability
• Hypothetical reasoning

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Informal Fallacies

• A fallacy is an error in reasoning.
• Fallacies of relevance When an argument relies
  upon premises that are not relevant to its
  conclusion, and therefore cannot possibly
  establish its truth
• Fallacies of weak induction When the connection
  between premises and conclusion is not strong
  enough to support the reasoning
• Fallacies of presumption, ambiguity, and
  grammatical analogy

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The Uses of Logic

• Evaluate someone elses argument by exposing its
  structure
• Set up your own argument
• Solve problems and puzzles by answering the
  why-questions (giving the reasons)
• Inference to the best through using the present
  evidences
• Thinking effectively and making decision wisely

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Logic and Critical Thinking

• Why should we become a critical thinker?
• Be the master of your own life
• To ask why? is to ask for the reasons for some
  beliefs and opinions (that is, to find out the
  premises for a certain conclusion)
• To evaluate how the reasons successfully support
  the claim (that is, to evaluate how the premises
  support the conclusion )
• A critical thinker is a truth-pursuer, and logic
  is truth-preserving.

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The End!