Critical Thinking Chapter 4

4 Deductively Strong, Inductively Strong, and Weak Arguments

We have been studying the logical form of arguments, separate from their content. That is, we’ve sought to recognize what is the nature of logical support even for a nonsense argument like:

No greeboks are bleen.
No bleen things are skeeb.

_________________________

Therefore, no greeboks are skeeb.

Even though these are nonsense claims and even though we don’t know what greeboks or skeebs are, we can see logically that this argument is deductively valid.

Now it is time to turn to the question of whether the premises in arguments actually are true and under what circumstances should we actually believe a conclusion on the basis of them. So now we will introduce the distinction of strong and weak arguments that builds on the account of valid, cogent, and ill-formed arguments we have established.

Deductively Strong Arguments

Very generally, strong arguments are ones whose conclusions we should accept because they support the conclusions well. A reasonable person believes the conclusions of strong arguments, and suspends judgment or disbelieves the conclusions of weak arguments.

Previously, we focused just on logical form of the arguments, but not the actual truth of the premises or conclusions. We saw that a valid argument is one where the premises, if they were true, would guarantee the truth of the conclusion. And a cogent argument is one that is invalid, and the premises, if they were true, would make the conclusion likely to be true. Ill-formed arguments are ones that are neither valid nor cogent.

Now we are going to add to the valid, cogent, and ill-formed concepts, by considering whether the premises are actually true. We saw earlier that for a claim to be true, what it asserts must match or reflect what is actually the case in the world. So the claim, "The Earth is round." is true because there is a planet, the Earth, that is round. (There are people who don't believe that this is true, but they are mistaken and they have a false belief.) Truth, we saw earlier, is objective and doesn't vary from person to person, although beliefs obviously can. When you reasonably believe a claim, then you think it is true. We are going to identify deductive arguments with valid arguments and inductive arguments with cogent arguments.

Here is the definition:

Deductively strong arguments meet two conditions:

For an argument to be deductively strong for a person S, it must be

a) valid

AND

b) it is reasonable for S to believe all of the premises.

This argument is probably deductively strong for you:

If you are a professor at CSUS, then you work in Sacramento.
If you work in Sacramento, then you work in California.
Professor McCormick is a professor at CSUS.

____________________

Therefore, Professor McCormick work in California.

The argument is valid, it follows a logical pattern such that, the premises, if they were true, would guarantee the truth of the conclusion. And furthermore, the premises actually are true. When you reflect on 1), 2) and on 3), you find them reasonable; you believe them. You think each of the premises are true. Recall from chapter 1 that to believe a claim is to take it to be true. So, as a result, you should believe the conclusion on the basis of this argument.

Here’s another argument that is deductively strong for you:

All whales are mammals.
All mammals have warm blood.

_________________________________

Therefore, all whales have warm blood.

The argument is valid, and provided that you believe that the premises are true, it is deductively strong for you.

Because the definition of a deductively strong argument invokes the concepts of reasonableness and belief, there is an element of subjectivity that has been brought into our discussion. Two people when considering the same premises might have different attitudes about their truth. Different background knowledge and different experience might lead one to think that a premise is true while the other might suspend judgment or reject that premise. So while validity is an objective property of argument--arguments are either valid or invalid, whether or not S recognizes it--the reasonableness of the premises will, to some extent depend upon the other views that S has, S's background information, S's evidence, and so on.

If the premises are reasonable for S to believe, that means that S thinks they are true. And if the argument is valid, then it is an argument where the truth of the premises would guarantee the truth of the conclusion. So S is rationally committed to accepting the conclusion. The argument supports the conclusion for S. A deductively strong argument, then, is the best argument one can give for a conclusion. If the argument is valid and you consider the premises are true, then you should accept the conclusion as true or reasonable. To reject the conclusion in those circumstances would be patently irrational.

What if the person considering the argument isn't sure whether one or more of the premises is reasonable? What if they suspend judgment about one or more of the premises? Are the conditions for a deductively strong argument met in that case? No. If you suspend judgment about a premise, then it wouldn't be true to say that it is reasonable for you to believe. You're not sure, so you wouldn't consider the premise and believe that it is true. So if a person suspends judgment about any of the premises, then the second condition for deductive strength is not met, and this argument cannot, therefore, be deductively strong. It will be weak in this case. We will say more about the various ways arguments can be weak shortly.

If S thinks that one or more of the premises are false, or even if S is not sure and suspends judgment about one or more of the premises, then the argument will not be strong for her. That is, the argument doesn't support the conclusion. The conclusion might be true, and the argument might be valid. It might even have all true premises. But unless S believes all the premises, they won't be adequate support to render the conclusion reasonable for her.

The validity of an argument is an objective property of the argument. It doesn’t vary from person to person. Also notice that validity has nothing to do with the premises or the conclusion actually being true. So a weird or silly argument like this one can be valid:

1. All inhabitants of the moon are Canadians.

2. Professor McCormick is an inhabitant of the moon.

_____________________________

3. Therefore, Professor McCormick is a Canadian.

The premises are both actually false in this case; There are no inhabitants of the moon, Canadian or otherwise, so premise 1 is false. And Professor McCormick is not an inhabitant of the moon, so premise 2 is false. However, IF these premises were true, they would guarantee the truth of the conclusion. So this argument is valid.

The concept of deductive strength now builds on the validity and asks the additional question, are the premises true? Do you find them reasonable? If an argument is valid and if you think the premises are true, then it is deductively strong for you. So this argument is deductively strong for you: :

1. There are no Americans currently living on the moon.

2. Professor McCormick is an American.

______________________________

3. Therefore, Professor McCormick is not currently living on the moon.

So it should be clear that whether or not an argument is deductively strong for a person will, in part, depend upon what that person believes, what background evidence they have, and the other beliefs that they have.

Let’s consider a fictional person and whether some arguments are deductively strong for him. Consider John who believes, like all of us do, that "If the earth was flat, then ships sailing on the ocean would fall off." And John also believes that, "Ships sailing on the ocean do not fall off." So when John considers this argument:

1. If the earth was flat, then ships sailing on the ocean would fall off.

2. Ships sailing on the ocean do not fall off.

___________________________________

3. Therefore, the earth is not flat.

it is deductively strong. It is valid, and S believes the premises, so the argument supports the conclusion and S should accept it (John does), or S is being irrational.

This argument is also deductively strong for John:

1. If my textbooks and teachers are reliable, then the earth is round.

2. My textbooks and teachers are reliable.

______________________________________

3. Therefore, the earth is round.

We could imagine someone else, however, Jake, who is suspicious and reluctant to believe his textbooks and teachers. He might have been misled by a textbook in the past or found an egregious error, or he might have had a really bad teacher who undermined his trust. So when Jake consider premise 2, he suspends judgment, or he even thinks it’s false. In this situation, this argument would not be deductively strong for Jake. One of the ways that arguments can be weak for a person S is if there are one or more premises that they suspend judgment about or reject as false. So this argument would be weak for Jake.

Consider this argument:

1. The United States wins every war it engages in.

2. The United States engaged in a war in Afghanistan.

________________________________

3. Therefore, the United States won the war in Afghanistan.

Suppose that John reflects on it and realizes there’s a problem with premise 1. He recalls that the war in Vietnam was a war that the United States engaged in, but did not win. So John disbelieves premise 1. He thinks premise 1 is false. The Vietnam war is a counterexample to 1. Premise 2 is true, John realizes. And the conclusion may turn out to be true (John doubts it.) But this argument is not good support for its conclusion because it has a false premise. Again, this argument is weak for John.

The same argument could be deductively strong for someone else, however. Suppose that Marion believes premise 1. Suppose that she had received a poor education and lots of people she trusts and believes, and who are normally good sources of information either never mentioned Vietnam, or they were mistaken about Vietnam too. So she believes 1. falsely. And she believes 2. And the argument is valid. So it meets the conditions of a deductively strong argument for Marion. But if Marion were to learn about Vietnam, and become convinced that that was a war that the United States lost, she’d cease to believe premise 1, and then the argument would be weak for Marion too.

What about this argument:

1. All Americans are Republicans.

2. Professor McCormick is an American.

________________________________

3. Therefore, Professor McCormick is a Republican.

This argument is not deductively strong for you, probably, because if you reflect on it, you’ll conclude that premise 1 is false. So this argument is weak for you.

Consider this argument. It is deductively strong for you?

1. All Americans are humans.

2. Professor McCormick is a human.

_______________________________

3. Therefore, Professor McCormick is an American.

It cannot be deductively strong for you because it doesn’t meet the validity condition; it’s ill-formed. The logical structure is neither valid nor cogent. Being ill-formed is another way an argument can be weak. If the logical structure is flawed, then an argument cannot give support to its conclusion. And notice that in this case, the premies and the conclusion are all actually true. The fact that premise 1, premise 2, and conclusion 3 are all true might lead someone who wasn’t being careful or deliberate to think that this is a good argument. With our argument analysis approach, however, we can separate the details and be specific. The premises and conclusion are all true, but this is a weak argument because its logical form is bad. Be on the lookout for these sorts of deceptive arguments, and take care to scrutinize first the logical structure of an argument independent of whether we agree with the claims, and then consider whether you believe the premises separately.

Now consider the important difference in this argument:

1. All Americans are humans.

2. Professor McCormick is an American.

___________________________

3. Therefore, Professor McCormick is human.

Now you should be able to see that this argument is deductively strong for you. It meets both conditions: it is valid (the premises, if they were true, would guarantee the truth of the conclusion) and the premises are true–a moment’s reflection makes it clear that all Americans are humans. And you probably believe premise 2, although your confidence about this claim might be weaker. If you’re genuinely not sure and suspend judgment about premise 2, then this argument would be weak for you.

Strong for One, Weak for Another: The same argument can be deductively strong for one person, weak for another because they think a premise is false, and weak for yet another because they suspend judgment about a premise. (And an argument can be weak for more than one reason; it might be invalid and you might reject or suspend judgment about more than one premise)

Learn the concepts in this chapter, then go to this custom ChatGPT agent to practice:

Argument Analysis AI

What this tool is: You have access to a custom argument-analysis practice tool designed specifically for this course. Think of it as a logic gym: you do reps, it checks your form, and it tells you precisely where you went wrong.

What skills you are training

This tool is designed to help you master three core classifications:

Deductively Strong (DS) arguments
Inductively Strong (IS) arguments
Weak (W) arguments

How to practice

When you ask the tool to quiz you, it will:

Present an argument.
Ask whether the argument is Deductively Valid, Cogent, or Ill-Formed.
Ask you, one premise at a time, whether you believe it (T), disbelieve it (F), or suspend judgment (SJ).
Ask whether the argument is DS, IS, or W for you.
If you say it is weak, require you to be specific about why (which premise, or why it is ill-formed, or how it is defeated).

Only after you commit to answers does it give feedback.

Feedback:

The feedback tells you:

whether you applied the definitions correctly,
whether your answers were internally consistent,
exactly which rule you misapplied, if any.

It does not:

tell you what to believe,
argue about politics, science, or morality,
penalize you for disagreeing with premises or conclusions.

You can call an argument valid and still judge it weak for you. That is a feature, not a bug.

How to use the tool effectively

To get the full benefit:

Practice until you are consistently correct on structure first (valid / cogent / ill-formed).
Get comfortable saying:
“This argument is valid, but weak for me because I reject Premise 2.”
Don’t rush. The point is accuracy, not speed.
Aim for at least ~80% correctness across multiple sessions.

If you can do that, you have the skills the course is testing.

Why this matters for your grade

The in-person quizzes and exams use the same structure as the practice tool:

same kinds of arguments,
same questions,
same definitions,
same distinctions.

The only difference is that the AI will not be there.

If you have practiced with the tool until the concepts are automatic, the in-person assessments will feel straightforward. If you have not, they will feel confusing and rushed.

Students who use the tool seriously should expect:

higher quiz scores,
more confidence identifying arguments,
fewer “I knew it but couldn’t explain it” moments.

This tool enforces the definitions used in this course. Philosophers can and do disagree about these definitions in other contexts. For this class, you are being graded on whether you can apply these definitions correctly and consistently.

Inductive Strength

Now let’s consider our second category of strong arguments. We will define inductively strong arguments this way: An argument is inductively strong for a person S when it meets three conditions:

1) it is cogent

AND

2) the premises are reasonable for S to believe.

AND

3) the argument is not defeated by S's total evidence.

So if you confront an argument that is cogent, and the premises are reasonable or true (you believe them), and if it is not defeated, then you should accept the conclusion as reasonable. The argument is inductively strong and gives you good grounds for accepting the conclusion. It won't guarantee the truth of the conclusion the way valid arguments will, but it does give good inductive, probabilistic justification for accepting the conclusion. It should be clear from what we learned about cogent arguments in the earlier chapter that while they give logical support to their conclusions, it is probabilistic and not as good as a valid argument.

What does it mean to say that an argument is defeated for a person S? Consider this argument:

The vast majority of humans have not walked on the moon.
Neil Armstrong is a human.

_____________________________

Therefore, Neil Armstrong has not walked on the moon.

Depending on what you know about the background here, this argument may be defeated for you. Neil Armstrong, famously, is the first person to walk on the moon in 1969. An argument is defeated when it meets three conditions:

The argument is cogent
S believes that all of the premises are true.
But S has background information leading them to believe that the conclusion is false.

We will be using the term “defeat” only in this technical sense; do not make the mistake of labeling an argument that has some other sort of problem like a false premise or being ill-formed as defeated. Being defeated in another way that arguments on our approach to argument analysis can be weak.

This version of the argument is inductively strong for you:

The vast majority of humans have not walked on the moon.
Professor McCormick is a human.

__________________________

Therefore, Professor McCormick has not walked on the moon.

This version is cogent, it has true premises, and it is not defeated. So it meets the conditions of being inductively strong.

Let’s consider some more cases to clarify the distinction between an inductively strong argument for S and one that is defeated and therefore weak. Reflect on this argument:

1) In the vast majority of cases, when a woman takes a home pregnancy test and gets a positive result, she is pregnant.

2) Caroline took a home pregnancy test and got a positive result.

__________________________________________________

3) Therefore, Caroline is pregnant.

This argument is cogent; it follows the pattern we've been considering for cogent arguments. Furthermore premise 1 appears to be true because home pregnancy tests are typically 98% or more accurate. You probably believe premise 1. And let’s stipulate that our hypothetical person, Caroline, also believes that premise 1 is true. What about premise 2? Suppose Caroline did take the test and she got a positive result, then she’d believe that premise 2 is true. So condition 2 for an inductively strong argument would be met.

Now let's consider two situations with regard to condition 3. Suppose that Caroline is a normal, healthy woman with no known medical issues and she's of child bearing age. She'd have no independent reasons to think, in that case, that she's in the 1-2% minority of cases where the test is not accurate or gives a false result. So in that case, she'd have no background information that might defeat or undermine the conclusion. So condition 3 would be met and this argument would be inductively strong for Caroline.

But suppose Caroline had this defeating piece of information: she also knows that A) she has an unusual medical condition that makes it impossible for her to get pregnant, and furthermore, one of the effects of her condition is that it makes her prone to test positive on pregnancy tests anyway. If A) was true and Caroline knew it, then the argument would still be cogent, and the premises are still true, but A) defeats the argument. In this case, the argument would not meet the third condition for being inductively strong. We add condition 3) for inductive strength because at best, cogent arguments would make their conclusions likely to be true if their premises are true, but there could still be a possibility that the premises are true but the conclusion is false. It can happen that the case being considered falls into the minority of cases not covered by the inductive generalization in premise 1. And S might have information that indicates that this is what has happened.

Let’s consider one more case of an argument that is inductively strong for one person and defeated, and therefore weak, for another person. Suppose that Ellen reads an article in a news sources she trusts that the article cites several reputable seeming studies that say most people in her neighborhood in Sacramento are Democrats. Then Ellen considers her neighbor Amy. She doesn't have any particular reason to doubt that Amy is an exception, or in the non-Democrat minority. So this argument:

Most people who live in Sacramento are Democrats.
Amy lives in Sacramento.

____________________________

Therefore, Amy is a Democrat.

is inductively strong for Ellen. It's cogent, it has true premises, and the argument is not defeated by Ellen's background information.

But Michael, who also knows Amy, and who knows that Amy lives in Sacramento, has listened to lots of anti-Democrat tirades from Amy. He's heard her say that she's a Republican and that she wouldn't be a Democrat if you held a gun to her head. And he thinks she's sincere. So the same argument is weak for Michael. The premises are true and that they are reasonable for Michael to believe; the argument is not weak because he rejects a premise. Furthermore, it’s cogent. Bu it is weak because it is defeated by his total evidence.

So, once again, an argument is defeated only under these circumstances: An argument is defeated for S if and only if, the argument is cogent, the premises are reasonable for S to believe, but S believes the conclusion is false because it conflicts with S's total background evidence.

And an argument is inductively strong for S when it meets these three conditions:

The argument is cogent
S believes each premise is true.
The argument is not defeated by S’s total background information.

Weak Arguments

Any argument that is not deductively strong or inductively strong is weak in our analysis. That is, the three categories are exhaustive. We’ve seen the ways that arguments can be weak along the way, but let’s enumerate the three ways arguments can be weak again for clarity. In general, a weak argument is one that fails to convince of us the conclusion. The conclusion might be correct, we might believe it. But the argument has some problem or problems that prevent it from giving good rational support.

There are three ways arguments can be weak: (and they can be weak for one or more of these reasons)

1) S believes one or more premises are false, or S suspends judgment about one or more premises.

That is, if you consider the premises and you think any of them are false (or more than one of them) or if you suspend judgment about any of them (or more than one of them), then the argument is weak.

Consider this argument:

1) All CSUS students are male.

2) Arnold Schwarzenegger is a CSUS student.

____________________________________

3) Therefore, Arnold Schwarzenegger is male.

A moment’s reflection should make it clear that premise 1 is false. Lots of CSUS students are female. If you are a female CSUS students, or you know one, then that’s a counter example to premise 1 proving it false. For universal generalizations of the form All As are Bs, a single case of an A that is not a B is counter example and decisively disproves it.

Furthermore, you might have a couple of different perspectives on premise 2). If you know who Arnold Schwarzenegger is (the famous action movie star, and former governor of CA), you probably doubt that 2) is true. You might not have as much conviction that 2) is false as your conviction that not all CSUS students are male, but you disbelieve it nevertheless. It seems unlikely that he’d be pursuing a degree at all, or at CSUS.

If you don’t know who Arnold Schwarzenegger is, then you should consider 2) and suspend judgment. If you don’t have any information about the claim one way or another, then the rational thing to do is to neither believe it nor disbelieve it. Remain open to be convinced by the evidence. But even in that case, this argument is now weak for you because you have suspended judgment about a premise.

So this argument is weak for you because it seeks to convince you that its conclusion is true on the basis of premises that you think are false or that you suspend judgment about. That’s not compelling grounds for the conclusion, even though the argument happens to be valid. False claims should not convince any reasonable person of anything.

2) An argument is weak if it is ill-formed. An ill-formed argument is neither valid nor cogent. So consider this example, and notice the difference from the previous argument:

All CSUS students are male.
Arnold Schwarzenegger is male.

__________________________________

Therefore, Arnold Schwarzenegger is a CSUS student.

This argument is invalid. Even if the premises were true, the conclusion would not be guaranteed to be true. Suppose all CSUS students were male, and that Schwarzenegger is a male. But those claims alone don’t support the inference that he's a student at CSUS. In fact, there are far more non-CSUS males than CSUS males on the planet, so 2. doesn't support the conclusion at all. It's an instance of affirming the consequent, a logical fallacy. Consider this parallel case to see the deep logical flaw in the structure of the argument:

1. All bears are mammals.

2. Dogs are mammals.

3. Therefore, dogs are bears.

In this case, the premises are in fact true. But the conclusion is false. This argument contains a serious logical error because of the relationships between the concepts.

Ill-formed arguments are neither valid nor cogent. This argument is not cogent either. A cogent argument is one that is 1) invalid, and 2) the premises, if they were true, would make the conclusion probably true. The premises here don't make the conclusion probable. In the first case, consider the class of all males and the tiny subset of that group that is the CSUS students who are males. The non-CSUS student males vastly outnumber the CSUS student males. So knowing that Arnold is a male doesn't make it likely that he is a CSUS student male. In fact, knowing that he is a male makes it unlikely that he's a CSUS student male because they are such a small percentage of over 3 billion males on the planet. Likewise with the second example. The non-bear mammals far outweigh the bear mammals. So knowing that dogs are mammals doesn't make it likely that they are bears, it makes it improbable. So these arguments are the opposite of cogent.

So an argument that is neither valid nor cogent is ill-formed. And being ill-formed is one of the three ways that an argument can be weak--by having bad logical form.

3) An argument is weak if it is defeated. Defeat happens in the specific circumstances listed above under the discussion of Inductively Strong arguments. That is, we have a specific, formal definition for the concept of defeat. It is not merely a bad argument or one that you don't accept.

An argument is defeated for S when:

It is cogent
S believes that all of the premises are true.
But S has background information leading them to believe that the conclusion is false.

This example is defeated for you:

1) Most citizens of the United States do not live in the White House.

2) The President of the United States is a citizen of the United States.

3) Therefore, the President of the United States does not live in the White House.

In this argument, the logical form is cogent. It follows the "1) Most As are Bs. 2) x is an A, 3) Therefore, x is a B," form that we have considered before for cogent arguments. And the premises are both true. There are over 330 million people in the United States, but only one of them lives in the White House. So most American citizens do not live in the White House. And we know that the constitution requires that the President be a citizen, so premise 2 must be true as well. However, I know that 3 must be false because of other information I possess. I know from watching the news, from my high school government class, and from sources I trust that the President is the one person who does live in the White House. And it’s probably defeated for you for the same reasons.

Critically Evaluating Arguments:

Now that we have this system for analyzing arguments and separating strong ones from weak one, we can say more about how to critically evaluate arguments. Strong arguments are ones that should convince a rational person to believe their conclusion. We now have a clear method for identifying deductively and inductively strong arguments. We also now have several specific ways to identify weak arguments and terminology for identifying their problems.

When we decide an argument is weak, and when we analyze them, we should:

Be clear and specific about exactly where the argument goes wrong. Is it the logical form (ill-formed) or do you doubt or reject one or more premises?
If it is ill formed, explain why; give another similarly structured argument that illustrates the mistake or fallacy. What is the logical problem?
If it’s a logical fallacy, then identify it specifically: affirming the consequent, denying the antecedent, confirmation bias, ….
If you suspend judgment about a premise, or think a premise is false, then say which premise, say whether you suspend judgment or whether you think it is false, and say specifically why you have doubts. Give your reasons for withholding your assent. Give examples, illustrate, explain.
Make the objection strong so that it shows the premise is mistaken. Recall the law of non-contradiction.
Counter examples. Recall that for a claim like All As are Bs, disproof comes from even a single instance of an A that is not a B. A single woman who is a good driver disproves that All women are bad drivers.
Disproving Most As are Bs. In order to disprove Most As are not Bs, you need to give convincing evidence that actually greater than 50% of As are not Bs. Polling data that shows that most college students are not Democrats, for example, shows that it’s not true that most college students are Democrats.
Defeated arguments have true premises, and they are cogent, but there is some crucial piece of information that shows that the conclusion does not follow. Even though most humans have not walked on the moon, Neil Armstrong is one of the minority who have.

Summary:

Here, again, are all of the important definitions so far:

A Valid argument is one where the premises, if they were true, would guarantee the truth of the conclusion.

A Cogent argument is 1) invalid, and 2) the premises, if they were true, would make the conclusion likely to be true.

An Ill-formed argument is one that is neither valid nor cogent.

A Deductively Strong argument is one that is 1) valid and 2) the premises are reasonable for you to believe.

An Inductively Strong argument is one that is 1) cogent, 2) the premises are reasonable for you to believe, and 3) it is not defeated by your total evidence.

Arguments can be weak three different ways:
- S believes one or more premises are false, or S suspends judgment about one or more premises.
- The argument is ill-formed
- The argument is defeated An argument is defeated when:
  - It is cogent
  - S believes that all of the premises are true.
  - But S has background information leading them to believe that the conclusion is false.

Flow Chart: And here is all of the information so far represented in a flow chart. Imagine asking these questions, from left to right, of an argument. Follow all of the branches to conclude whether it is deductively strong, inductively strong, or weak:

Argument Analyses:

The AI tutor for this chapter will train you how to do a particular sort of argument analysis based on what we’ve learned so far. Here are a few examples of how we can apply these concepts to arguments. For our tests and for the course, you’ll need to demonstrate your mastery of all of the above concepts by being able to correctly do the analyses below:

Covid Vaccine Argument

If a vaccine is approved by the FDA, then it has been shown to be safe and effective in controlled clinical trials.
The Covid vaccine has been approved by the FDA

____________________________

Therefore, the Covid vaccine has been shown to be safe and effective in controlled clinical trials.

Argument analysis:

a. Is the argument Valid, Cogent, or Ill-formed? _________

b. Do you (or the person in the example) think the premises are True, False, or do you Suspend Judgment? 1.____ 2._____

c, Is the argument Deductively Strong, Inductively Strong, or Weak? _________

d. If it is weak, why? _______________________________________

Flat Earth Argument

If the Earth were flat, then ships sailing on the ocean would fall off.
Ships sailing on the ocean do not fall off.

––––––––––––––––––––––––––

Therefore, the Earth is not flat.

Argument analysis:

a. Is the argument Valid, Cogent, or Ill-formed? _________

b. Do you (or the person in the example) think the premises are True, False, or do you Suspend Judgment? 1.____ 2._____

c. Is the argument Deductively Strong, Inductively Strong, or Weak? _________

d. If it is weak, why? _______________________________________

Astrology Argument:

The predictions in my astrological forecast are accurate some days.
If the predictions in my astrological forecast are accurate some days, then astrology works.
If astrology works, then I should consult my astrology forecast when I make big decisions.

__________________________________

Therefore, I should consult my astrology forecast when I make big decisions.

Argument analysis:

a. Is the argument Valid, Cogent, or Ill-formed? _________

b. Do you (or the person in the example) think the premises are True, False, or do you Suspend Judgment? 1.____ 2._____ 3._____

c. Is the argument Deductively Strong, Inductively Strong, or Weak? _________

d. If it is weak, why? _______________________________________

Undocumented Immigrants Argument

A high rate of undocumented immigrants are coming through the American border illegally.
If a high rate of undocumented immigrants are coming through the American border illegally, then the U.S. is failing to maintain its border.
Any country that fails to maintain its border will have its social, legal, and political structure ruined.

______________________

Therefore, the U.S. will have its social, legal, and political structure ruined.

Argument analysis:

a. Is the argument Valid, Cogent, or Ill-formed? _________

b. Do you (or the person in the example) think the premises are True, False, or do you Suspend Judgment? 1.____ 2._____ 3._____

c. Is the argument Deductively Strong, Inductively Strong, or Weak? _________

d. If it is weak, why? ___________________________________________

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