Critical Thinking Notes - Lecture notes, lectures 1 - 7 PDF

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Critical Thinking- Week 1 Notes What is Critical Thinking? • Critical thinking is about evaluating beliefs. • Critical thinking is not about where your beliefs come from. • Sociology and psychology study why we believe what we believe. • It’s about which beliefs are worth having. • We assume a belief is worth having provided it’s most likely true. • We also assume a belief is most likely true if there are good reasons to accept it. “Critical thinking is the systematic evaluation or formulation of beliefs, or statements, by rational standards.” • It’s systematic because it involves distinct procedures and methods (not just gut feelings). • It’s used to evaluate existing beliefs and formulate new ones. • It evaluates beliefs in terms of how well they are supported by reasons. We Should Think Critically Because:  Who we are is determined largely because of our actions and choices  Our actions and choices are in turn determined by our thoughts and beliefs  If we don’t choose our beliefs carefully were giving up control. Critical Thinking is all about thinking OUTSIDE of the box:  Its about challenging our assumptions  Asking hard questions  Rejecting biases, stereotypes, and other unreasonable assumptions To Think Critically you need to be able to think, listen, and read slowly and attentively. It helps you understand a few definitions and concepts. DEFINITIONS: Assertion (statement) : An Assertion is a declarative sentence that is intended to make a claim of some sort. Sometimes these are called statements or propositions. “Im taller than you” “it is raining” “she will win the race.” Not all sentences are declarative. Questions are not assertions. Premise: A statement offered in support of a conclusion. Conclusion: A conclusion is a statement that is held to by supported by a premise or premises.

Premise: All Whales are mammals Premise: Moby Dick is a whale Conclusion: Moby Dick is a Mammal. Argument An argument is a set of statements one of which (the conclusion) is taken to be supported by the remaining statements (the premises). Here’s another way of saying this: • An argument is a group of statements in which some (the premises) are intended to support another (the conclusion). • The conclusion is what the speaker wants you to accept. • The premises state the reasons or evidence for accepting the conclusion. • An argument must have a conclusion; the idea of what is the claim in the passage that an individual is trying to persuade you of. • Typical argument will have mini claims to support it. Inference: An inference is the move from a premise (or premises) to a conclusion (or conclusions). • Critical thinking is all about inferences. • Inferences are identified and evaluated. Explanation and Argument should not be confused.  An explanation tells you why something happened  An argument tells you why you should believe something, an argument tries to persuade you.  Arguments have something to prove; explanations do not Example; 1. Adam stole the money, for three people saw him do it 2. Adam stole the money because he needed it to buy food Not all statements contain arguments:  To recognize arguments look for a conclusion and look for a premises.  These can often be identified by certain indicator words such as: Conclusion- Indicators  Thus  Therefore  Hence  Entail(s)  … it follows that …  … we may conclude …  Consequently  So Premise- Indicators • Since • Because

• • • • •

For As … given that … … inasmuch as … … for the reason that …

Two Points About Indicator Words First: They may not actually be present in arguments. Second: In arguments, premises do not always come before conclusions; conclusions do not always come after premises “textual priority versus logical priority.” “Religious beliefs cannot be proven. If something is a matter of faith, it cannot be proven, and religious beliefs are obviously a matter of faith.” Truth Versus Logical Strength; • Premises and conclusions may be true, or they may be false. • Evaluating the truth-value of premises and conclusions is distinct from evaluating the logical strength of arguments. (1) Ryerson University is in Guelph, ON. (2) The RAC is located within Ryerson U. ___________________________ Therefore, 3) The RAC is located in Guelph, ON. Validity and Soundness. Deductive Validity: An argument is deductively valid if and only if it is not possible for the premises to be true and the conclusion false. i.e., if all the premises were true, the conclusion would have to be true too. An argument is deductively invalid if and only if it is not deductively valid. A deductively valid argument: (1) All bachelors are unmarried. (2) Ivan is a bachelor. ____________________________ Therefore, (3) Ivan is unmarried. Note: This is a special use of the word ‘valid’ Remember, a valid argument need not have true premises, and it need not have true conclusions: what’s important is the logical relationship between the premise(s) and conclusion(s). (1) All Americans are ten feet tall. (2) Prof. Hunter is an American .

Therefore, (3) Prof. Hunter is ten feet tall Two False Premises and False Conclusion. Deductive Soundness: An argument is deductively sound if and only if it is deductively valid and all its premises are true. Deductive Versus Inductive Arguments In a deductively valid argument, the truth of the premise(s) guarantees the truth of the conclusion(s). But, not all arguments are deductive: Inductive Strength: An argument is inductively strong if and only if the conclusion is probably true, given the premises. An argument is inductively weak if and only if it is not inductively strong.

***** In the case of any argument the point is not whether the premises/conclusions are actually true or false, its weather supposing that the premises were true they would guarantee that the conclusion is true too. If they would the argument is valid.

Inductively Strong Argument: (1) Quitting smoking usually improves your health. (2) Mary has quit smoking. Therefore, probably (3) Mary’s health will improve. Inductively Weak Argument: (1) A few police officers are corrupt. (2) Jim is a police officer. Therefore, probably, (3) Jim is corrupt.

Critical Thinking- Week Two Notes:  Impediments to CT

Critical Thinking is the systematic evaluation or formulation of beliefs or statements by rational standards. Common Impediments to Critical Thinking: Category 1: Hindrances that arise because of how we think Category 2: Hindrances that occur because of what we think. Category 1 impediments to Critical Thinking (a) Self- interested thinking: Accepting a claim SOLELY on the grounds that it advances or coincides with our interests. Overcoming Self- Interested Thinking:  Watch out when things get very personal  Be alert to ways that critical thinking can be undermined( ex; wishful thinking)  Ensure that nothing has been left out  Avoid Selective Attention  Look for Opposing evidence. (B) Group Thinking: Peer Pressure  Fallacy: An argument form that is both common and defective.  Fallacy of appeal to popularity  Fallacy of appeal to common practice  Fallacy of appeal to tradition  Genetic Fallacy. Stereotyping: Drawing conclusions about people or groups without sufficient reasons. Some Terminology Concerning Knowledge:  Knowledge has to be beliefs that are true.  Different uses of “knowledge.”  Knowledge by acquaintances  Knowledge- how  propositional

Critical Thinking- Week 3 Notes – Chapter 1 & 2 quiz next week.  Follow study guide for quiz next week, things that are not on the study guide, are not on the quiz.  Study guide covers his slides and the textbook.

 Few passages will be given, and will be asked if its an argument if it’s an argument it will be asked to give the premises and conclusions. (Chapter 1).  I’ll be asked to explain category 1 and category 2 impediments.  Bring Pen! Deductive Argument: • A deductive argument is intended to provide conclusive support for its conclusion. • A deductive argument that succeeds in providing conclusive support for its conclusion is said to be valid. • One that fails to provide conclusive support is said to be invalid. • A valid argument is such that if its premises are true, then its conclusion must be true. • For this reason, deductively valid arguments are said to be truth-preserving. • Valid is same as truth preserving. • If the premises are truth the conclusion MUST be true. • Not all deductively valid arguments have true premises and true conclusions. • In fact, a valid argument may have any of the following combinations: • True premises and true conclusion • False premises and true conclusion • False premises and false conclusion • The only combination a valid argument may not have is true premises and false conclusion. • Explanation: if it’s a valid argument it must be truth preserving, if the premises are true the conclusion must be true. • A deductively valid argument with true premises is said to be sound. • Sound means argument is valid and all of the premises are TRUE. • A sound argument can have a false conclusion. FALSE statement. In fact, we don’t even need to know the truth-value of the premises and conclusions in order to know that an argument is valid. Consider: (1) Either Jones or Smith committed the murder. (2) Jones didn’t commit the murder. .: (3) Smith committed the murder.  Inspection of the logical structure of this argument, by itself, tells us that it is valid.  Our test for validity: suppose that the premises are all true. Then, ask yourself: supposing that the premises are true is it possible for the premises to be false? If it is not possible, the argument is valid.  Inductive argument would state what something probably would be the case.  Inductive arguments are never valid.

(ii) Inductive Arguments 1. An inductive argument is intended to provide probable support for its conclusion. 2. An inductive argument that succeeds in providing probably support for its conclusion is said to be strong. A strong inductive argument is such that if its premises are true, its conclusion is probably true. 3. A strong inductive argument with true premises is said to be cogent. 4. Because the conclusion of an inductive argument is not guaranteed to be true by the truth of the premises, inductive arguments are not truth-preserving.  Cogent Means Strong- If the premise is true than the conclusion is probably true.  Cogent inductive argument can have a false conclusion - > False. Inductively Strong Argument: (1) Quitting smoking usually improves your (2) Mary has quit smoking. Therefore, probably (3) Mary’s health will improve. Inductively Weak Argument: (1) A few police officers are corrupt. (2) Jim is a police officer. Therefore, probably, (4) Jim is corrupt.

health.

Chapter Two The Environment of Critical Thinking: Impediments to CT: Impediments to critical thinking classified Recall our first definition: Critical thinking is the systematic evaluation or formulation of beliefs or statements by rational standards. Common impediments to critical thinking: Category 1: hindrances that arise because of how we think. Category 2: hindrances that occur because of what we think. Category 1 Impediments to Critical Thinking (a) Self-Interested thinking: accepting a claim solely on the grounds that it advances, or coincides with, our interests. Overcoming self-interested thinking:  Watch out when things get very personal.

 Be alert to ways that critical thinking can be undermined (ex: wishful thinking).  Ensure that nothing has been left out:  Avoid selective attention.  Look for opposing evidence. (b) Group Thinking:  Peer pressure Fallacy: an argument form that is both common and defective.  Fallacy of appeal to popularity  Fallacy of appeal to common practice  Fallacy of appeal to tradition  Genetic fallacy  Stereotyping: drawing conclusions about people or without sufficient reasons.

groups

Some Terminology Concerning Knowledge. Different uses of “knowledge”:  Knowledge by acquaintance  Knowledge-how  Propositional knowledge (knowledge-that) Three key ingredients in Propositional knowledge:  Belief  Truth  Justification Referred to as Tri Partied conception of knowledge; Knowledge has these three parts. Our goal is to have a lot of knowledge, and have evidence that would support our claims. 5) Category 2 Impediments to Critical Thinking. Hindrances that occur because of our views about truth and knowledge.  Subjective Relativism.  Social Relativism.  Skepticism. If you do not believe there is an objective truth, than you are a relativist. Relativism: the view that intentions have a truth-value, but that what this is depends upon (i.e. is relative to) some person or social group. (i) Subjective Relativism The view that the truth-value of a proposition depends solely upon (is relative to) what some subject believes. “ that’s true for you “

“ that’s my truth” Objections: (a) This is unlikely: consider the jar of jelly beans (b) This view would make us (Infallible-> meaning you believe you cant make an error) (c) This view is self-defeating (i.e. if it’s true, then it is an example of a truth that is not relative). Subjective relativist is saying there is no absolute truth.

(ii) Social Relativism The view that the truth-value of a proposition depends solely upon (is relative to) societies. It is talking about something more broad. Why might someone hold this view? Objections: (a) Implausible (b) Intolerant views (c) Would make societies infallible (infallible means you believe that you cannot make an error.) (c) Self-defeating. Philosophical Skepticism: o The view that propositions have truth-values, but that we know what very few, or none, of them are. o (In other words, we know a lot less than we think, or nothing at all.) Why Hold this View? (a) Dream Hypothesis (b) Evil Genius Hypothesis e.g. Machine hypothesis

René Descartes (1596-1650)

Consider the following argument for skepticism: (1) Unless I am completely certain that I am not being deceived by an evil genius, my beliefs lack justification (they do not count as knowledge). (2) I am not completely certain that I am not being deceived by an evil genius. Therefore, (3) My beliefs lack justification (they do not count as knowledge). Objection:

 Requiring absolute certainty for a belief to count as knowledge is asking too much.

Each category 2 impediments to critical thinking denies something about truth or knowledge: Relativism- subjective RelativisimNEXT STEPS:  Review Chapters 1 & 2: do the exercises in the textbook (pp.52-60). Feel free to skip the “Writing Exercises” on pp.61-63.  Go to the online study guide, and work though the exercises and interactive quizzes for Chapters 1 and 2 until you feel you have mastered the material.  Review Quiz #1 Study Guide (to be posted early next week).  Attend and participate in your one-hour tutorial. (On your weekly class schedule, you’ll see the word “lecture” in the onehour time-slot for SSH105. Don’t be misled: this is, in fact, your tutorial.) Memorize you section #. You will need to write this on your tests/exams!!!

Critical Thinking Week 4: Lecture Topics: 1. Deductive Vs. Inductive Arguments 2. Deductive Argument Patterns 3. Diagramming Arguments. Conditional Statement: Conditional statement is a statement of the form If P, Then Q. Example:  If it rains the picnic will be cancelled  If Jones didn’t commit the murder the butler did. 

Conditions are compound statements composed of two parts:

 

The Antecedent: What follows the word “if” The Consequent- What follows the word “then”

 Conditional is a compound statement it is an If and Then Statement. 

When doing a scheme of argument of abbreviation NEVER break up a conditional.. a Conditional is always saying one thing.



By Contrast a Conjunction is telling two things…. Ex; it rained and then the picnic was cancelled.

 

A Conditional is a promise. Ex; if you pass the course; Ill Buy you a donut. The Idea that if you meet a certain condition than someone will buy you a donut.

Conditionals make a single assertion and that assertion is thought of as a promise or a guarantee.

Disjunctive Statements: 

A Disjunctive Statement is a statement of the form.



Either P or Q

Examples;  Either the picnic was cancelled or it rained  Either Jones committed the murder or the butler did Disjunctions are compound statements composed of two parts called the disjuncts.

Some Valid Conditional Argument Patters. 1. Affirming the Antecedent ( Modus Ponens): If P, then Q. P. Therefore, Q. Example; 1. The conservative won the election, then Stephen harper is the new prime minister. 2. The conservatives won the election. 3. Therefore, Stephen Harper is the new prime minster. Always in a conditional the antecedent expresses a sufficient condition

Some Valid Conditional Argument Patterns. 3. Denying the Consequent( Modus Tollens) If P, Then Q.

Not Q. Therefore, Not P Example; 1. If the liberals won the election, then Paul Martin is the new prime minister 2. Paul martin is not the new prime minister 3. Therefore, The liberals did not win the election.

The consequent in a conditional always expresses what is a called a necessary condition.



Antecedent equal sufficient conditions for the consequence.



The consequent expresses a necessary condition

Hyopothetical Syllogism If P, then Q. If Q, then R Therefore, if P then r. Example; (1): If the conservatives won the election, then stepher harper is the new Prime Minister. (2) If Stephen Harper is the new Prime Minister, then someone from Alberta I s the new prim minster (3) Therefore, if the conservatives won the election then someone from albera is the new prime minister.

Denying the Antecedent: ( Invalid) If P, then Q. Not P Therefore, Not q. Example;

If it’s a square it has 4 sides It isn’t a square Therefore, its not a square

Example; If Einstein invented the computer, then he’s a genius Einstein did not invent the computer Therefore, he’s not a genius

Affirming the Consequent ( Invalid) If p, then q Q, Therefore P

A Valid Disjunctive Argument Pattern Disjunctive Syllogisms: Either P or Q Not P Therefore, Q. Either P or Q Not Q Therefore , P.

Diagramming Arguments Before evaluating an argument, therefore it often helps to reconstruct it in a more perspicuous manner. One way make DIAGRAM of argument. Method for Diagramming Arguments: Step 1: Underline premise and indicator words Step 2: Find conclusion and draw line under It Step 3: Locate the premises and draw a line under them Step 4: Cross out statements, irrelevant sentences, questions, exclamations. Step 5: Draw the diagram.

Critical Thinking- Week 6 Notes:

Conditional statements and necessary conditions vs Sufficient Conditions  

“ A is necessary condition for B”, means “without A, B would not be true.” A” is a sufficient condition for B” Means “ If A is true, then B would have to be true as well.” (e.g) If john is a bachelor, then John is unmarried. The Consequent- “John is unmarried”- expresses a necessary condition for its being true that John is a bachelor; If It was false than he could not possibly be a bachelor. But being unmarried is not sufficient for being a bachelor one must also be male. The Antecedent Condition- “John is a bachelor”- expresses a sufficient condition for its being true that John is unmarried. If it were true that John is a bachelor, then it would have to be true that he is unmarried. But being a bachelor is not necessary condition for being unmarried. Women are often unmarried, although they are never bachelors.

Diagramming Arguments:  Before evaluating an argument, it often helps to reconstruct it in a more perspicuous manner. ONE way is t...