Logic Thinking What is Logic Logic is the

Logic Thinking

What is Logic? • Logic is the study of the rules for correct, or valid, reasoning. • It is about argumentative that we do to find support for our reasoning • Involve the Deduction and Induction process of reasoning • Logic is happening in our daily life, everyday we use logic thinking • Logical analysis is a process that comes naturally to the human mind • Process where we are more familiar than we realize

TYPES OF ARGUMENTS Deductive arguments § An argument in which it is impossible for a conclusion to be false if its premises are true. § The conclusion claims to follow necessarily from the premises. § Example: § All math classes are time-consuming. All hard classes are math classes. Therefore, it necessarily follows that all hard classes are timeconsuming. Inductive arguments § An argument in which it is improbable for the conclusion to be false if its premises are true. § Conclusion claims to follow probably from the premises. § Example: § Socrates was Greek. Most Greeks ate fish. Therefore, Socrates probably ate fish.

Deduction Reasoning • Reasoning that moves from the general to the specific. • It is a form of inference where if the premises are true, the conclusion must also be true. • Start with a rule and then apply it to new situations. • Use syllogism Example: – All humans have two legs (major premise) – I am a human, (minor premise), – Therefore, I have two legs (conclusion). Example: The law of gravity says that what goes up must come down, so I bet if I throw this ball up it will fall back down.

Induction Reasoning • Reasoning that typically moves from specific examples to a larger, general conclusion. • start with your own experience and then generalize a rule. • If the premises are true, it is probable that the conclusion is false. Example: -Tony dog’s bark when see people -All dog will bark when see people Example: Last few times I cut my hair, it grew back. after this when I cut my hair it will always grow back.

Deduction is the logical process of arriving at a conclusion based on premises you KNOW to be true. Induction is the logical process of arriving at a conclusion based on premises you ASSUME to be true.

Test Your Logic! Which way the bus is going? Left or right ?

HOW DO WE TELL INDUCTIVE FROM DEDUCTIVE? The distinction between inductive and deductive arguments is based on the strength of an argument’s inferential claim. § Reminder: An inferential claim is based on a certain reasoning process – it is the relationship between the premises and conclusion of an argument. But the strength of a claim is hardly ever stated outright, so we have to evaluate it. § Three criteria for measuring an argument’s strength: § 1) The occurrence of special indicator words. § 2) The actual strength of the inferential link between the premises and conclusion. § 3) The form of argumentation used by the person making the argument. Certain indicator words lean more towards inductive and some lean towards deductive. But they’re not always accurate. Pay attention to the context of the argument. § Example: The word “probably” tends to be used in inductive arguments, and words like “therefore” and “necessarily” tend to lean towards deductive arguments.

FORMS OF DEDUCTIVE ARGUMENTS Argument based on mathematics § The conclusion depends on a mathematical or geometric measurement. § Has to be deductive since it follows necessarily --- meaning there’s no room for it “probably” being right. § Example: 1+1 = 2 § There’s no room for a different answer by reevaluating the argument. 1 + 1 will always equal 2. If you have 1+1, then it’ll always equal 2. Argument from definition § The conclusion is claimed to depend on the definition of a word or phrase used either in a premise or in the conclusion. § They follow necessarily because the argument depends completely on the definition of the word being used. § Example: John is a kleptomaniac, so it follows forth that he steals things. § The argument is deductive since the definition of the word leads the argument to one conclusion alone.

MORE DEDUCTIVE FORMS Categorical syllogisms § Made up of exactly two premises and one conclusion. Begin with the words “all”, “some”, and “no”. (We’ll discuss these in much more detail in Chapter 5). § Example: § “All ancient forests are sources of wonder. Some ancient forests are targets of the lumber industry. Therefore, some sources of wonder are targets of the lumber industry. Hypothetical Syllogisms § Syllogisms (two premises and one conclusion) that have a conditional statement for one (or both) of its premises. § Example: § “If monopolies continue to grow, then suppliers will be squeezed even further. If supplies are squeezed even further, then jobs will be forced overseas. Therefore, if monopolies continues to grow, then jobs will be forced overseas. § If you have A, then you have B. § If you have B, then you have C. § Therefore, if you have A, then you have C. § Hypotheticals work like chains…one leads to the next and ties them all together.

What Is a Syllogism? A specific method of Logical Deduction (moving from the general to the particular) Every syllogism contains at least three parts: – a major premise (global assumption) – a minor premise (specific claim, ) – a conclusion (a statement that follows logically from and is consistent with both the major and minor premises). • It’s kind of like simple math If A = B and B = C, then A = C

INDUCTIVE ARGUMENT FORMS Prediction § An argument that works based off our knowledge of the past in order to make a claim about the future. § Example: § There tends to be a lot of rain in the Midwest, so it will probably rain there tomorrow. § Claims about the future can’t be known with any certainty, so they can’t be absolutely true, even though they can be justified. That makes them inductive. Argument from analogy § Depends on the existence of an analogy (or similarity) between two separate things. § Example: § My Honda gets good gas mileage. § So it follows that John’s Honda also gets good gas mileage. § The truth of an argument like this is based on chance, so and that chance makes it an inductive argument.

MORE INDUCTIVE ARGUMENT FORMS Generalization § An argument that is applied to a whole group based on knowledge gained from a small sample of people. § Example: § Five out of ten people in Ellis Hall said they support abortion. So I can say that half of Athens supports abortion. § Statistical data is not always accurate, so the truth of this form of argument can not be made certain. It remains only probable. Argument from authority § An argument that concludes something is true because an expert said it is. § Example: § Centrum vitamins work because Dr. Jones did a study that proved it. § This type of argument is only true with probability since studies can be wrong or mistaken.

EVEN MORE INDUCTIVE ARGUMENT FORMS Argument based on signs § Conclusion based on knowledge gained from a sign about what the sign claims to mean. § Example: § A sign on the side of the road says “School Zone” so I can assume that a school is somewhere up ahead. § The sign could have been moved from somewhere else, or it could simply be wrong, so it can’t be true with absolute certainty. Causal inference § Argument that proceeds from knowledge of a cause to a claim about its effect, or vice versa, that knowledge of an effect can provide information about its cause. § Example: § I left a soda in the freezer last night, so I can assume that it is frozen.

THINGS TO KEEP IN MIND Overlaps can happen between arguments. § Example: If one triangle has its hypotenuse as length X, then a congruent triangle will also have a hypotenuse as length X. § This can be mistaken for an argument for analogy because you’re comparing two triangles. § But it’s dealing with math, so it has to be an argument based on mathematics. Arguments dealing with science are unique, though. § Dealing with the discovery of a scientific fact are typically inductive, since their reliability hasn’t been proven yet. § There a few exceptions, but for our purposes scientific arguments are deductive when they deal with the application of a scientific fact.

What are the unstated assumptions? • I failed that course because the instructor didn’t like me. Assumption: The instructor fails students he doesn’t like. • I’m not surprised he made the team. After all, his father is the superintendent of schools. Assumption: The superintendent gives special favors to his family • If I’d only taken my boss to lunch more often, I could have gotten that raise. Assumption: The boss denies raises to people who don’t take him to lunch very often. Analyze the assumptions behind every idea!!!

All men are mortal. Socrates is a man. Therefore, Socrates is mortal. One ringgit will buy three candy bars. I have one ringgit. Therefore, I can buy three candy bars. All cars need gasoline to run. I have a car. Therefore, my car needs gasoline to run

How About This? All old people are bad drivers Abu is an old person. Abu is a bad driver. Valid Argument But Not True Is it true Abu is a bad driver?

True VS. Valid Arguments True Argument • an argument with a conclusion that is considered factually correct. Valid Argument • an argument with a conclusion that makes sense logically, regardless of whether it is true or not

Is this True, Valid, or Both? • All fruits have seeds. • Tomatoes have seeds. • Therefore, a tomato is a fruit. All fruits Scientifically, this is valid and true Tomatoes

Is this True, Valid, or Both? • No human being is immortal. • Ghosts are not human beings. • Therefore, ghosts are immortal. human beings all things immortal ghosts Faulty logic because this syllogism assumes anything not human is immortal. However, according to some people’s beliefs, this is a true statement: So this is an invalid argument, but a true conclusion.

Is this True, Valid, or Both? • All weeds are plants. • A flower is a plant. • Therefore, all weeds are flowers. plants weeds flowers The conclusion here does not logically follow as a necessary consequence; therefore this argument is invalid.

Fallacy

What is Fallacy? • Error in reasoning • Differ with factual error • Fallacy is an "argument" in which the premises given for the conclusion do not provide the needed degree of support • Misconception resulting from incorrect reasoning in argumentation. • Fallacies are statements that might sound reasonable or superficially true but are actually flawed or dishonest

PERSONAL ATTACK Poisoning the Well“ Ø Attacking or praising the people who make an argument, rather than discussing the argument itself. Ø Personal character of an individual is logically irrelevant to the truth or falseness of the argument itself Ø Appeal to Force ("Might-Makes-Right" ): This argument uses force, the threat of force, or some other unpleasant backlash to make the audience accept a conclusion. It commonly appears as a last resort when evidence or rational arguments fail to convince a reader.

-Abusive Ø This persuasion comes from irrational psychological transference rather than from an appeal to evidence or logic concerning the issue at hand. -Circumstantial Ø To argue that an opponent should accept an argument because of circumstances in his or her life.

Genetic Fallacy Ø The genetic fallacy is the claim that an idea, product, or person must be untrustworthy because of its racial, geographic, or ethnic origin. Argumentum ad Populum Ø Bandwagon Approach: “Everybody is doing it. ” Majority of people believes an argument or chooses a particular course of action, the argument must be true, or the course of action must be followed, or the decision must be the best choice.

-Patriotic Approach: Ø "Draping oneself in the flag. " This argument asserts that a certain stance is true or correct because it is somehow patriotic, and that those who disagree are unpatriotic. -Snob Approach Ø “all the best people are doing it. ”

Type of Personal Attacks Ad Hominem Attacking the individual instead of the argument. • You are so stupid your argument couldn't possibly be true. • I figured that you couldn't possibly get it right, so I ignored your comment. Appeal to Force • If you don't want to get beaten up, you will Telling the hearer that agree with what I say. something bad will happen to him if he does • Give it or die. not accept the argument. Poisoning the Well Presenting negative information about a person before he/she speaks so as to discredit the person's argument. • Frank is arrogant and thinks he knows everything. So, let's hear what Frank has to say about the subject. • Don't listen to him because he is a loser.

Appeal to Pity Urging the hearer to accept the argument based upon an appeal to emotions, sympathy, etc. Example: Oh come on, I've been sick. That's why I missed the deadline. Genetic Fallacy • The genetic fallacy is the claim that an idea, product, or person must be untrustworthy because of its racial, geographic, or ethnic origin. • Attempting to endorse or disqualify a claim because of the origin or irrelevant history of the claim. Example: Frank just got out of jail last year; since it was his idea to start the hardware store, I can't trust him.

Appeal to the Popular @ Argumentum ad Populum Urging the hearer to accept a position because a majority of people hold to it. Example: The majority of people like soda. Therefore, soda is good. Bandwagon Approach: “Everybody is doing it. ” Majority of people believes an argument or chooses a particular course of action, the argument must be true, or the course of action must be followed, or the decision must be the best choice Snob Approach: Patriotic Approach: "Draping oneself in the “all the best people are flag. " doing it. ” This argument asserts attempting to prove a that a certain stance is conclusion by true or correct because appealing to what an it is somehow patriotic, elite or a select few and that those who (but not necessarily an disagree are authority) in a society unpatriotic. thinks or believes.

You have to choose between 3 rooms • The first is full of raging fires • The second is full of tigers that haven’t eaten for 3 years • The third is fully of assassins with loaded machine guns Which room should you choose?

THE END Thank You