Some Basic Concepts Highlights of Chapter 1, 2, 3.
What is Critical Thinking? Not Critical as in judging severely to find fault. Critical as in careful, exact evaluation and judgment. Critical Thinking refers to a set of skills relating to the recognition, analysis, evaluation, and construction of arguments.
Bloom s Taxonomy of Learning Objectives
How is Critical Thinking useful? Critical thinking skills are necessary for: success in college success in the workplace success in the marketplace Success in life
Developing Critical Thinking Skills Understand the concepts. Practice! Practice! Practice! Apply the skills.
Arguments for critical thinkers.. An argument is a set of claims; one of which is supported by the others. other words for claims are proposition statement This is a slightly different concept then a sentence.
Identifying Claims A claim is a statement that has truth-value. It is snowing. Barack Obama is the 44 th President of the United States. Today is Saturday. Alaska is bordered by the Mediterranean Sea. Buffy is a vampire slayer.
Identifying Claims Not all sentences are claims. It is cold in Alaska. Where is Alaska located? Please take me to Alaska. Let s go to Alaska. Yea, Alaska! Hint! Test using it is true that
Descriptive vs. Evaluative Claims Capital punishment is the lawful infliction of death as a penalty for committing a crime. Capital punishment is immoral. Note: Both are claims!
Counting Claims A single claim can be expressed in different sentences. Mike voted for Harper. He voted for Harper. Harper is who Mike voted for.
Counting Claims A single sentence can represent different claims. She went to the store. Could mean. Sarah went to Superstore. Jane went to Sobeys.
Counting Claims A single sentence may contain more than one claim. George owns a cat, and Jones owns a dog. George owns a Siamese, which is a breed of cat. George got a new cat because his other one died.
Try it Identify the two claims expressed in the sentence, Dr. Newberry s class is held in room 106, which is in the southern side of Dorothy Donahoe Hall.
Try it Identify the two claims expressed in the sentence, Phil s class is held in room EDU224, which is in the Education building. Claim 1: Phil s class is held in room EDU224. Claim 2: Room EDU224 is in the education building.
Counting Claims Multiple claims can be combined in a sentence to form a single claim. We can go to the park or we can stay home. If you complete all your homework, then you will be prepared for class.
Complex claims: Why does the sentence Sally owns a cat and Jim owns a dog express two claims, while Sally owns a cat or Jim owns a dog expresses only one? Well, stay tuned
So What is an argument? An argument is a set of claims; one of which is supported by the others. The conclusion is the claim that the arguer is trying to prove. Claims called premise(s) provide support for the conclusion.
Arguments. Monty Python was right! An argument is a connected series of statements intended to establish a proposition. John Cleese et al. http://montypython.50webs.com/scripts/series_3/27.htm
Arguments. How arguments work Arguments are a series of claims connected so that one or more of them support another. All Dogs are Canines All Canines are Mammals All Dogs are Mammals.
Argument: Ordinary Language. In ordinary language, an argument is a heated discussion between 2 or more people who disagree. In logic, an argument is 2 or more statements intended to be related so that one is justified by the other(s). Sometimes its both!
Parts of an argument Arguments are composed of One or more premises. (the reasons) Exactly one conclusion. Example: P1. I buy beer for Markers who find plagiarists. P2. Markers love beer. P3. Markers have no money. C. My Markers will try hard to find Plagiarists.
Inference indicators are words and phrases which identify the parts of the argument. Inference indicators help us understand how the claims in an argument are related.
Inference Indicators Conclusion Indicators therefore thus consequently so... hence accordingly Premise Indicators because since for given... as follows from
Arguments vs. Explanations Both contain at least two claims. Both provide reasons. Different purpose. Arguments offer reason why something is true. Explanations describe how or why something is true.
What is an explanation? An explanation is a set of claims accounting for how or why a given fact is true. The explanandum is the fact being explained. The explanans is the account offered for some given fact.
Arguments vs. Other Non-Arguments A passage may be neither an argument nor an explanation because: It contains only one claim, or None of the claims provides reasons for any of the others. A to-do list is neither an explanation nor and argument.
Recognizing Arguments Step 1: Count the claims Arguments must contain two or more claims. Step 2: Look for reasons Arguments contain a claim that is supported by the other(s). Step 3: Identify the purpose Arguments offer proof that a claim is true. Explanations describe how or why a fact is true.
Is it an argument? Police are looking for a suspect who robbed a local gas station two weeks ago. Video from the station s security camera shows a man walking into the store with a gun, pointing it at the cashier, and exiting the store with cash from the register. No injuries have been reported. I was terrified because all I saw was this gun, and I really thought that he was going to shoot me. We believe that the suspect in this case is the same one responsible for two other gas station robberies that occurred earlier this month. The physical descriptions are very similar, and the same kind of weapon was used in all three incidents.
Tangent: Truth Values In our culture, we presume that every statement is either true or false. This is the 1 st law of thought. Sometimes called the law of the excluded middle. Do you agree with this presumption? Truth values can change: It is raining outside is false right now, but will eventually be true.
True and False In logic we often speak of the truth value of statements. Ex: It is true that the Titanic sank. Ex: It is false that Phil is thin. Don t confuse Good with true and Bad With False. Ex: 50 Million died in WWII True but horribly bad. Ex: There is a cure for cancer. False but something we hope to be true soon.
What makes something true? Believe it or not We don t really know. This is a genuine philosophical question. There are many different theories. Correspondence theory: Truth is what agrees with reality. Commonsense but problematic Coherence theory: Truth is what agrees with our current beliefs. There are many other theories
Logic without truth Philosophers and logicians have developed a system that can evaluate statements and arguments without having to confirm things as true or false. This is handy if you can t agree what true or false is. Examples in logic courses tend to stick to very obviously true or false claims, rather then those claims that are contentious.
Valid In ordinary language: often used as a synonym for Good. Daytime TV is full of people with valid opinions who make valid points. Don t use valid this way (for this class)! Try to never use it this way! Valid has a very precise technical meaning.
What Valid really means. A valid argument is one that guarantees the truth of the conclusion whenever the premises are true. Example Valid argument. All dogs are canines. No Cats are canines. No dogs are cats.
But, valid is a conditional concept Arguments whose premises are false, but which would guarantee the conclusion if the premises are true, are still valid. Eg: valid argument with false premises. All dogs are cats. Obviously false. (O.F.) All cats are whales. OF All dogs are whales. OF
Think of it this way If all dogs were cats, and If all cats were whales Then all dogs would be whales. Valid is a description of arguments, not parts of arguments (which can be either true or false)
More odd Valid arguments. All dogs are cats. OF All cats are canines. OF All dogs are canines. Obviously true. If all dogs were cats and all cats were canines, Then it would be true that all dogs are canines. This example illustrates that the falsity of the premises doesn t imply the falsity of the conclusion.
This is a valid argument All X are Y All Y are Z Therefore all X are Z. Despite the fact that you don t know what X, Y or Z represent. Ignore Actual truth or falsity when considering validity, concentrate on the relationship between the premises and the conclusion.
Examples of invalid. All dogs are mammals. All cats are mammals. All dogs are cats. O.F. All dogs are mammals All cats are mammals No dogs are cats. (all true, but still invalid for reasons as follows )
How do you know that is invalid? Any argument that permits a counterexample is invalid. A counterexample is an argument with the same form as the original argument, but which has obviously true premises and an obviously false conclusion.
Counterexample Example Original argument All x are y All z are y No x are y. Counterexample: All fish are cold-blooded. All spiders are cold-blooded. Therefore no fish are spiders.
Using Counterexamples Counterexamples are a form of PROOF that an argument is invalid. They are also effective in contexts where people don t know their logic. Someone who has never studied reasoning can often be convinced by ear that their argument is flawed with the presentation of a counter example.
Providing counter examples. Take the original argument: Identify the form (the structure of the argument) Think of another argument with the same form but with obviously true premises and an obviously false conclusion. Ex next page.
Original argument All presidents are charismatic men. Mitt is a charismatic man, Mitt will be president. Counterexample: Fill in the blanks. P1 All are P2. is C: will be
Fallacies and Counterexamples In the next section of the course we will study the fallacies We will use a lot of counter-examples to help understand why these arguments are fallacies.
Logical Fallacy Two senses: Any argument that fails to adequately support its conclusion. It is impossible to define all the ways you can be wrong. Any argument that fits into common patterns of error in reasoning. The fallacies.
To be a fallacy To be a fallacy a series of statements must first be an argument: You re a jerk, therefore you re wrong. Is a fallacy (ad hominem aka fallacy of abuse.) You re a jerk, is not a fallacy, it is mere abuse.
Fallacies in this course We will look at 4 sets of fallacies: Informal fallacies. Fallacies of syllogistic logic. Fallacies of propositional logic. Fallacies of inductive logic. Formal fallacies.
Example of a fallacy Childhood obesity has increased now that so many children are playing video games, so obviously video games cause obesity in children. This argument relies on the evident fact that video games and obesity have occurred together to conclude one is the cause of the other.
Cum hoc, ergo procter hoc A common causal fallacy, know by its traditional latin name: With this, therefore because of this. Counterexample: (to expose the fallacy) Video games have been gradually increasing in popularity since the 80 s, and my hair has been decreasing since then, so obviously video games have caused my baldness.
Formal versus Informal fallacies Formal fallacies are fallacies that violate some specific logical rule or law. Ex: All Geese can fly All ducks can fly All geese are ducks. This argument commits the formal rule regarding the distribution of terms in an argument.
Formal versus Informal fallacies Formal fallacies are fallacies that violate some specific logical rule or law. Ex: All Geese can fly All ducks can fly All geese are ducks. The category of things that can fly includes both ducks and geese. The way this argument refers to flying things, they can be either ducks or geese, but not necessarily both. This argument commits the formal rule regarding the distribution of terms in an argument.
Formal vs informal fallacies Informal fallacies are not violations of specific logical rules Instead are errors of reasoning common enough to be named, recognized, and studied. Traditional education in law often focused heavily on the informal fallacies. Informal fallacies are often grouped by category in various ways. There are many different groupings in different texts.
Copi s treatment of the Fallacies Copi groups 19 informal fallacies into 3 groups. Fallacies where the primary deficiency is Relevance R1-R7. Presumption P1-p7. Ambiguity A1-A5.
Additional sources for Fallacies www.fallacyfiles.org Extensive collection of fallacies. http://www.nizkor.org/features/fallacies/ Collection of fallacies relevant to the website: rebutting holocaust deniers. http://onegoodmove.org/fallacy/ This site indicates a proof condition for each fallacy given.