Let's Learn Some Logic

[Gary Childress]

Introduction: The thread title is self explanitory. We'll see if this thread gets off the ground or not. I truly hope it does because I think logic is something valuable for all of us to learn and know. Or if you already know a lot about logic this is a good time to share some of that knowledge with others or even brush up on it to keep yourself sharp.

I've been struggling with logic in my philosophy courses I'm currently taking online at The University of Illinois - Springfield and had the idea that maybe with the help of others here at CFC I may be able to re-learn logic and in the process make it a mutual learning experience for others who may or may not be familiar with the subject or who may also need to polish up on their logic skills as well. In effect this thread could be a kind of study group for those of us interested in sharpening our logic skills.

What is Logic: Logic is a powerful tool for evaluating arguments. In many ways it resembles mathematics in the use of proofs and formulas to evaluate whether an argument is a good one or not.

Few would dispute that 2 + 2 = 4. The intent of logic is to create a basis whereby arguments can be evaluated and disputes settled in much the same way as in mathematics. Using logic we can all become better at criticizing the arguments of others and at better advancing our own arguments. Many of us may know what a fallacy is and how to spot some of them. But how many of us know how to construct a good argument of our own which can be proven to be a good one?

Some personal background: I first took Logic 101 at George Mason University back in the late 1980s and did pretty well at it. Unfortunately I've since forgotten almost everything I once Knew. However, I still have my old textbook and some vague memory of the knoweldge I once possessed.

The plan is this: (I hope it works. ) This thread will start at the beginning and work its way up step by step through the text book cited below. Included in the thread will be logical excercises found in the book with which to better sharpen our skills. Unfortunately only some of the excercises in the book have answers to them provided at the end of the book. I WILL NOT BE POSTING EXERCISES THAT HAVE THE ANSWERS IN THE BACK OF THE BOOK. Rather than me having the unfair advantage of knowing what the answers are I will only post excercises which have no answers given but which we can all discuss and debate the answers to.

In this OP I will post the table of contents of the text book and as I cover each section I'll see if I can figure out how to post a link to the post where the discussion of the section begins. That way it will be possible to go to this OP and quickly navigate to where you want in the discussion.

The Text Book: A Concise Introduction to Logic, 3rd ed., by Patrick J. Hurley, (California: Wadsworth Publishing Company, 1988)

The text book is broken into 9 chapters which are further broken down into a total of 54 sections. Each section slowly builds upon the preceding sections from the simpler to more complex logical operations. At the end of each section are exercises designed to practice what has been learned. Some of these exercises I will post for open debate. I hope to cover a good deal of ground in a reasonable amout of time. Maybe 2 sections or more per week. That way the whole book is finished in maybe half a year or less.

CONTENTS​

CHAPTER 1: BASIC CONCEPTS
1.1 Arguments, Premises, and Conclusions
1.2 Recongnizing Arguments
1.3 Deduction and Induction
1.4 Validity, Truth, Soundness, Strength, Cogency
1.5 Argument Forms: Proving Invalidity
1.6 Extended Arguments​

[More to follow as we progress....]

NOTE: Please feel free to jump into the discussion even if you are not interested in logic, you may find it entertaining to pop in once in a while and offer a criticism or two based upon what is posted. And please don't feel ashamed to step off the high horse and learn with the rest of us. This will hopefully be an opportunity for all to benefit.

 

[Gary Childress]

CHAPTER 1: BASIC CONCEPTS
SECTION 1.1 ARGUMENTS, PREMISES, AND CONCLUSIONS (Hurley, pp. 1-14)

What is an argument: An argument is more or less a group of statements. A statement is a sentence that is either true or false. True and false are the two possible truth values of a statement.

Here are some of my own examples of statements:

1. Pearl Harbor was bombed by the Germans.
2. War and Peace was written by Ernest Hemingway.
3. Water is composed of two hydrogen atoms and one oxygen atom.
4. Paris is the capital city of France.​

The truth value of #1 and 2 are "false". The truth value of #3 and 4 are "true".

Many sentences are not statements and cannot be said to have a truth value to them. Examples of sentences which are not statements and do not have truth values are questions, proposals, suggestions, commands and exclamations.

Below are some of my own examples of sentences which are not statements:

[question] What is the capital of Japan?
[proposal] Let's study logic today.
[suggestion] It would probably be best to take the bus to get downtown.
[command] Don't drink the orange juice.
[exclamation] Most definitely!​

An argument contains one or more premises and only one conclusion. Premises contain the evidence for an argument. The conclusion is what is claimed to follow from the evidence presented in the premise(s).

My own example of an argument (also a famous example given in logic):

Socrates is a man
All men are mortal
Therefore, Socrates is mortal​

The first and second statements are the premises and the third is the conclusion. The word "therefore" is probably the most typical giveaway that a statement is the conclusion but not all conclusions use the word "therefore". In the argument above the conclusion is said to follow from the statements and in this case the conclusion does indeed follow from the premises. Because the conclusion does follow from the conclusion the argument is a good one.

An example of a bad argument.

Socrates is a man
Some men are tall
Therefore, Socrates is tall​

In this case the conclusion does not follow from the premises. Or the evidence does not support the conclusion.

Being able to recognize the correct structure of an argument is crucial in determining whether or not an argument is a good one.

The text book gives the following list of conclusion indicators on p. 3

therefore
wherefore
accordingly
we may conclude
entails that
hence
thus
consequently
we may infer
it must be that
whence
so
it follows that
implies that
as a result​

Statements following such indicators are usually but not always the conclusion of an argument.

My own example:

"Smoking is hazardous for a person's health. But tobacco corporations need to make a profit in order to survive. Consequently there is a conflict of interest between tobacco corporations and public health."​

The conclusion of the argument is that there is a conflict of interest between tobacco corporations and public health. The premises are that smoking is bad for a person's health and that tobacco corporations need to make a profit in order to survive.

Indicators for premises can be (Hurley pp. 3-4):

since
as indicated by
in that
may be inferred from
seeing that
for the reason that
because
for
as
given that
inasmuch as
owing to​

Sometimes a conclusion can be discerned by using the above to separate the premises from the conclusion.

My own example:

Since drunk driving is a leading cause of traffic fatalities, there should be laws to discourage it.​

In this case none of the usual conclusion indicators are present. but the word since gives away the premise; "drunk driving is a leading cause of traffic fatalities" and "there should be lawas to discourage it" is the conclusion.

Sometimes an argument needs to be sifted out of a passage which contains no clear indicators of what the premises are or what the conclusion is.

My own example:

There should be laws to discourage drunk driving. Drunk driving is a leading cause of traffic fatalities. Furthermore there is no reason for anyone to drink alcohol before they drive a vehicle.​

In this case the argument would be analyzed as follows:

P1: Drunk driving is a leading cause of traffic fatalities.
P2: there is no reason for anyone to drink alcohol before they drive a vehicle
C: There should be laws to discourage drunk driving.​

When restructuring arguments it is important to try to use the original verbage as much as possible so as to avoid error.

An argument can sometimes contain statements within it that are neither premises nor conclusion and need not be included in the analysis of it.

My own example:

People should not be allowed to smoke in public places. Second hand smoke has been proven to have the ability to cause health problems. This is basically why I'm very sensitive to the topic.​

The statement: "This is basically why I'm very sensitive to the topic" is neither a premise nor a conclusion and need not be factored into the analysis of the argument.

The reasoning process expressed by an argument is called an inference and the terms argument and inference are often used interchangeably.

The meaning or information content of a statement is called a proposition. Proposition and statement are often used interchangeably.

This concludes the first section.

 

[Gary Childress]

Final post for today: Some exercise questions form the text book (pp. 8-14)...

I. Identify premises and conclusions of each argument presented below. Again these are selected questions which do NOT have the answers in the back of the book So they are open for debate and critique:

#2. Since the good, according to Plato, is that which furthers a person's real interests, it follows that in any given case when the good is known, men will seek it.
(Avrum Stroll and Richard Popkin, Philosophy and the Human Spirit)

My anwer:

Spoiler :

P1: The good, according to Plato, is that which furthers a person's real interests.
C: In any given case when the good is known, men will seek it.

#3. As the denial or perversion of justice by the sentences of courts, as well as in any other manner, is with reason classed among the just causes of war, it will follow that the federal judiciary ought to have cognizance of all causes in which the citizens of other countries are concerned.
(Alexander Hamilton, Federalist Papers, No. 80)

My answer:

Spoiler :

P1: The denial or perversion of justice by the sentences of courts, as well as in any other manner, is with reason classed among the just causes of war.
C: The federal judiciary ought to have cognizance of all causes in which the citizens of other countries are concerned.

#8. Like a flame or the wake of a boat, the form of a plant changes slowly but the components are in continual flux. The motion of the components can therefore be analyzed in terms of fluid flow.
(Ralph O. Erickson and Wendy Kuhn Silk, "The kinematics of Plant Growth")

My answer:

Spoiler :

P1: Like a flame or the wake of a boat, the form of a plant changes slowly but the components are in continutal flux.
C: The motion of the components can be analyzed in terms of fluid and flow.

#11. Since the drive for profits underlies the very existence of business organizations, it follows that a most important function of an accounting system is to provide information about the profitability of a business.
(Walter B. Meigs and Robert F. Meigs, Accounting)

My answer:

Spoiler :

Your turn to answer this one...

#14. Women of the working class, especially wage workers, should not have more than two children at most. The avergae working man can suport no more and the average working woman can take care of no more in decent fashion.
(Margaret Sanger, Family Limitations)

My answer:

Spoiler :

Your turn again...

#20. Contrary to the tales of some scuba divers, the toothsome, gaping grin on the mouth of an approaching shark is not necessarily anticipatory. It is generally accepted that by constantly swimming with its mouth open, the shark is simply avoiding suffocation. This assures a continuous flow of oxygen-laden water into their mouths, over their gills, and out through the gill slits.
(Robert A. Wallace et al., Biology: The Science of Life)

My answer:

Spoiler :

P1: It is generally accepted that by constantly swimming with its mouth open, the shark is simplyi avoiding suffocation.
P2: This assures a continuous flow of oxygen-laden water into their mouths, over the gills and out through the gill slits.
C: Therefore contrary to the tales of some scuba divers, the toothsome, gaping grin of the mouth of an approaching shark is not necessarily anticipatory.

#24. Though it is possible that REM sleep and dreaming are not necesary in the adult, REM deprivation studies seem to suggest otherwise. Why would REM pressure increase with deprivation if the system is unimportant in the adult?
(Herbert L. Petri, Motivation: Theory and Research, 2nd ed.)

My answer:

Spoiler :

P1: According to REM deprivation studies REM pressure increases with deprivation.
C: This seems to suggest that REM sleep and dreaming are necessary in the adult.

 

[Global Skeptic]

...

My own example:

Since drunk driving is a leading cause of traffic fatalities, there should be laws to discourage it.​

In this case none of the usual conclusion indicators are present. but the word since gives away the premise; "drunk driving is a leading cause of traffic fatalities" and "there should be law as to discourage it" is the conclusion.

Sometimes an argument needs to be sifted out of a passage which contains no clear indicators of what the premises are or what the conclusion is.

My own example:

There should be laws to discourage drunk driving. Drunk driving is a leading cause of traffic fatalities. Furthermore there is no reason for anyone to drink alcohol before they drive a vehicle.​

In this case the argument would be analyzed as follows:

P1: Drunk driving is a leading cause of traffic fatalities.
P2: there is no reason for anyone to drink alcohol before they drive a vehicle
C: There should be laws to discourage drunk driving.​

When restructuring arguments it is important to try to use the original verbage as much as possible so as to avoid error.

An argument can sometimes contain statements within it that are neither premises nor conclusion and need not be included in the analysis of it.

I am not sure that - P2: There is no reason for anyone to drink alcohol before they drive a vehicle - is a statement like water is composed of two hydrogen atoms and one oxygen atom. Rather it appears to be a conclusion itself based on a series of not stated statements. Note I am not sure. In other words I am unsure if it is sound or even valid as a premise.

 

[Global Skeptic]

CHAPTER 1: BASIC CONCEPTS
SECTION 1.1 ARGUMENTS, PREMISES, AND CONCLUSIONS (Hurley, pp. 1-14)

What is an argument: An argument is more or less a group of statements. A statement is a sentence that is either true or false. True and false are the two possible truth values of a statement.
...

Yes, in principle any statement is either true or false, but in practice the truth value of certain statements can be unknown. Further the LNC in one interpretations only states that either S or non-S is false, but says nothing about the truth of S or non-S.

 

[Gary Childress]

I am not sure that - P2: There is no reason for anyone to drink alcohol before they drive a vehicle - is a statement like water is composed of two hydrogen atoms and one oxygen atom. Rather it appears to be a conclusion itself based on a series of not stated statements. Note I am not sure. In other words I am unsure if it is sound or even valid as a premise.

Hi Global Skeptic, thank you for participating in the discussion. I believe-- I can't recall for sure-- but I believe "validity" and "soundness" apply to arguments and not premises. It may indeed be true that the premise is disputable. The example given in the book at that point is:

The space program deserves increased expenditures in the years ahead. Not only does the national defense depend upon it, but the program will more than pay for itself in terms of technollogical spinoffs. Furthermore, at current funding levels the program cannot fulfill its anticipated potential.​

I think at this point the important point is to be able to discern how to pick an argument out of a passage and lay it out in a fashion in which it can be analyzed by logic and not so much whether the arguments themselves are good ones and should convince us of anything or not.

I agree that the premise differs from the sort of premise that water is H2O but as we all know arguments are often made about things which are debateable and not easily resolved in dispute. I think there will probably be a great many disputable arguments given as examples in the days ahead.

As far as truth value being unknown, that is often the case as well. I think one of the limits of logic is that it can tell us whether an argument is a good one or not but it cannot tell us of the rightness or wrongness of premises. That is something that must be discerned by the one participating in an argument. Logic cannot tell us if it is true that "drunk driving is a leading cause of traffic fatalities". But it can tell us if the conclusion necessarily follows from the premises or not. Logic can tell us that if I accept premise 1 and premise 2 in an argument as true that I must accept the conclusion if the argument is a good one.

 

[Global Skeptic]

As I remember it:

(Hidden premise as not stated, that all penguins are animals)
P1: All penguins can swim.
P2: All swimming animals are fish.
Conclusion: All penguins are fish.

Then conclusion is valid ->
P is S
S is F
Therefore: P is F
Or if you like
All penguins are swimming animals
All swimming animals are fish
Therefore: All penguins are fish

But all swimming animals are fish is not sound(true). So valid is as I remember it if the conclusion follows(deduction) from the premises and sound whether the premises are true.

 

[Gary Childress]

Looking in the back of the text book at the glossary it says:

Sound argument: A deductive argument that is valid and has true premises.

Valid deductive argument: An argument in which the premises support the conclusion in such a way that if they are assumed true, it is impossible for the conclusion to be false.

All penguins are swimming animals
All swimming animals are fish
Therefore: All penguins are fish

So the argument above is a valid argument because it's structure makes it impossible for the premises to be true and the conclusion false, however not a sound argument because at least one of the premises is not true. So yes, it appears you are correct.

 

[Ayatollah So]

In #20 I see two arguments or sub-arguments. What you call P2 justifies P1, which in turn justifies C. I say so because P2 actually does support P1, and a discourse should be regarded as an argument, in the absence of reasons not to, if the argument would be successful.

 

[Save_Ferris]

The problem is that logic can't really be taught. It's a natural mental function. It only can really be considered when a logical fallacy arises.

And that is my excuse for not reading about it

 

[Gary Childress]

In #20 I see two arguments or sub-arguments. What you call P2 justifies P1, which in turn justifies C. I say so because P2 actually does support P1, and a discourse should be regarded as an argument, in the absence of reasons not to, if the argument would be successful.

Hi Ayatollah So,

Thanks for the feedback. Yeah, looking at it now, something does look a little awkward about #20. I think you make a good observation.

Perhaps it would be better to combine P1 and P2 in the following way:

P1: It is generally accepted that by constantly swimming with their mouths open, sharks are simply avoiding suffocation by assuring a continuous flow of oxygen-laden water into their mouths, over the gills and out through the gill slits
C: Therefore contrary to the tales of some scuba divers, the toothsome, gaping grin of the mouth of an approaching shark is not necessarily anticipatory.

@Save_Ferris: I don't know why anyone would think that logic is unteachable. This seems as good an opportunity as any to learn.

 

[Antilogic]

Subscription post for now, I hope to follow along despite the clear irony of my username.

 

[Gary Childress]

Welcome Antilogic! Glad to have you aboard!

I'll do my best to keep things interesting. Working on section 1.2 now as we speak! Will try to have it posted soon.

 

[Gary Childress]

SECTION 1.2 RECOGNIZING ARGUMENTS (Hurley, pp. 14-23)

As with section 1.1 I'm going to keep things as brief and concise as possible since we're really dealing with a lot of common sense here, though there is more terminology to be introduced of course. As we progress further into the book and get into the more interesting stuff, I'll try to go into more detail.

Section 1.2 can pretty sufficiently be summed up in three parts:

In part I. we distinguish between arguments and several other types of non-arguments. Whereas an argument is intended to prove something, non-arguments are not.

Here are some non-argument types:

Warnings:

Example: Be careful of the wet floor.​

Pieces of Advice:

Example: It might be best to take the bus if you are going downtown.​

Statements of belief or opinion: If there is no evidence or reason given for the author's opinion, then there is no argument.

Example: Blue would be a good color for the stairway.​

Descriptions:

Example: The Eiffel tower is a puddled iron lattice tower located in Paris, France. It reaches a height of 1063 feet with 3 floors and 9 elevators.​

Reports: Are similar in some ways to descriptions but conveys information about an event or situtation:

Example: Lewis and Clark set out on their expedition in 1804 from a staging area near Hartford Illinois.​

NOTE: Sometimes reports can be about arguments such as in a newspaper piece:

Example: Authorities believe that since the gunman escaped in a getaway car there was more than one suspect involved in the robbery.​

In the case above one may address the argument of the authorities but note that it is not the author's argument.

Expository passages: These can often be mistaken for arguments and can seem very close at times. The author's intent is not to prove something but expand or better develop a topic.

Example: Listening to Richard Strauss' Also Sprach Zarathustra, one is reminded of the life of Nietzsche himself. The tone poem is accented with seeming moments of joy and epiphany contrasted with sorrow and melancholy to match the dynamic character of Nietzsche's own life as portrayed in his seminal work Thus Spoke Zarathustra.​

The passage above is not intended to prove the first statement so much as it is intended to exand on it.

Illustrations: Can also often be confused with arguments as they may employ words such as "thus" which might normally lead one to believe an argument is being made. In some cases such passages can be interpreted as containing arguments.

Example: Illustrations may contain the word "thus" and are often employed to exemplify a statement. Thus illustrations can often be interpreted as containing an argument.​

The passage above may or may not be considered an argument supporting the conclusion that "illustrations can often be interpreted as containing an argument". But generally illustrations are intended to exemplify a statement.
​

In Part II. we look at conditional statements.

Conditional statements are "if...then..." statements.

Example: If it begins to thunder, then our dog will become frightened.​

The part of the statement following the word "if" is called the antecedent. The part folling the word "then" is called the consequent.

Conditional statements are not arguments but are often employed in arguments. So for instance in the example above neither the antecedent nor the consequent are said to be true but rather it is asserted that if something is the case then something else will follow as a consequent. Also note conditional statements don't always express causal connections. for instance "If it begins to thunder, then the New York Yankees will win the world series" is also a conditional statement but the antecedent and consequence are not causally connected.

Some conditional statements can be similar to argument in which case, in some instances, a conditional statement can be reexpressed as an argument.

Example: "If thunder scares my dog, then it is likely he will run under the table." can be reexpressed as:​

Thunder scares my dog
Therefore it is likely he will run under the table.

In logic, conditional statements are generally used to express the relationship between necessary and sufficient conditions.

If an antecedent cannot occur without the consequent, then is is considered A necessary condition. If the antecdent is "sufficient" for causing the consequent, then is it said to be a sufficient condition.

Examples:

If it thunders, then my dog will run under the table.
If it thunders, then there must be clouds somewhere.​

In the first statement thunder is a sufficient condition for causing my dog to run under the table. In the second statement there being clouds somewhere is a necessary condition for thunder.
​

Part III. is concerned with explanations.

Explanations are also sometimes mistaken for arguments. because they often contain the word "because", an indicator word for arguments. Explanations contain two components; the explanandum and the explanans. Basically the explanans explains the explanandum.

Examples:

My dog ran under the table because it's afraid of thunder.
The computer began to power up because I hit the power button.
The painting is above the stairwell because I hung it there.​

Whereas an argument tries to prove that something is the case and explanation tries to show why something is the case. Explanations and arguments may both contain inferences. Explanations may be re-expressed as arguments.

Example:

I hit the power button, therefore the computer shut down.​

Exercises will follow later this evening...

 

[innonimatu]

In #20 I see two arguments or sub-arguments. What you call P2 justifies P1, which in turn justifies C. I say so because P2 actually does support P1, and a discourse should be regarded as an argument, in the absence of reasons not to, if the argument would be successful.

It's not just #20, all the examples seem to be of deductive logic where two premises are chained, leading to a conclusion. Examples:

#2. Since the good, according to Plato, is that which furthers a person's real interests, it follows that in any given case when the good is known, men will seek it.

P1: The good furthers a person's real interests.
P2 (left unstated but assumed): a person seeks to further their real interests.
C: A person will seek the good.

#3. As the denial or perversion of justice by the sentences of courts, as well as in any other manner, is with reason classed among the just causes of war, it will follow that the federal judiciary ought to have cognizance of all causes in which the citizens of other countries are concerned.

P1: The denial or perversion of justice by the sentences of courts is classed among the just causes of war.
P2 (again unstated but assumed): The federal judiciary ought to have oversight over possible causes of war.
C: The federal judiciary ought to have cognizance of all causes in which the citizens of other countries are concerned.

#11. Since the drive for profits underlies the very existence of business organizations, it follows that a most important function of an accounting system is to provide information about the profitability of a business.
(Walter B. Meigs and Robert F. Meigs, Accounting)

P1: The drive for profits is fundamental to the existence of businesses (according to Meigs&Meigs...).
P2 (assumed): Accounting exists to serve the needs of businesses.
C: A most important function of an accounting system is to provide information about the profitability of a business.

For deductive logic to be backed then the assumed premises should be stated. Consider the original example:

Socrates is a man
All men are mortal
Therefore, Socrates is mortal

We could have written simply: "Socrates is a man, therefore Socrates is mortal". Any human reader would understand it and fill in the assumed "all men are mortal". But if you programming that logic, or formally stating it, you must state all the premises.

 

[Gary Childress]

It's not just #20, all the examples seem to be of deductive logic where two premises are chained, leading to a conclusion. Examples:

#2. Since the good, according to Plato, is that which furthers a person's real interests, it follows that in any given case when the good is known, men will seek it.

P1: The good furthers a person's real interests.
P2 (left unstated but assumed): a person seeks to further their real interests.
C: A person will seek the good.

#3. As the denial or perversion of justice by the sentences of courts, as well as in any other manner, is with reason classed among the just causes of war, it will follow that the federal judiciary ought to have cognizance of all causes in which the citizens of other countries are concerned.

P1: The denial or perversion of justice by the sentences of courts is classed among the just causes of war.
P2 (again unstated but assumed): The federal judiciary ought to have oversight over possible causes of war.
C: The federal judiciary ought to have cognizance of all causes in which the citizens of other countries are concerned.

#11. Since the drive for profits underlies the very existence of business organizations, it follows that a most important function of an accounting system is to provide information about the profitability of a business.
(Walter B. Meigs and Robert F. Meigs, Accounting)

P1: The drive for profits is fundamental to the existence of businesses (according to Meigs&Meigs...).
P2 (assumed): Accounting exists to serve the needs of businesses.
C: A most important function of an accounting system is to provide information about the profitability of a business.

For deductive logic to be backed then the assumed premises should be stated. Consider the original example:

Socrates is a man
All men are mortal
Therefore, Socrates is mortal

We could have written simply: "Socrates is a man, therefore Socrates is mortal". Any human reader would understand it and fill in the assumed "all men are mortal". But if you programming that logic, or formally stating it, you must state all the premises.

Hi innonimatu,

A very astute observation. You're probably right about these. Since we haven't yet gotten to valid forms of argument, filing in missing premises might be a little ahead of the game right now. You may need to wait for those of us on the slow track to catch up to you.

For right now, suffice to say that simply discerning premises from conclusions is probably all the book is mainly interested in.

I hope to get through the first few chapters relatively quickly so we can get to the fun part as soon as possible but I don't want to skip anything.

In the meantime, just as a little bit of a teaser...

Eventually one of the (many) things we'll all be learning is how to determine if the following is a valid or invalid argument using indirect truth tables without constructing a 256 line truth table:

We'll be learning what the different symbols mean in propositional logic and how to take a series of premises like the above and derive their conclusions when the conclusions aren't given. We'll also be covering Venn Diagrams and lots of other neat stuff.

I promise all will be revealed to those interested in learning. The really great thing about logic is it isn't really that difficult once you learn the basics. If you have any understanding of mathematics then logic will be a pushover for you. For those ahead of the game right now, please be patient with the rest of us. We'll all be getting there soon.

As always, thank you for your interest!

 

[Gary Childress]

EXERCISES FOR SECTION 1.2

Directions from the book: "Determine which of the following passages are arguments. For those that are, identify the conclusion. For those that are not, attempt to determine whether they are warnings, pieces of advice, statements of belief or opinion, descriptions, reports, expository passages, illustrations, conditional statements or explanations."

#2. If public education fails to improve the quality of instruction in both primary and secondary schools, then it is likely that it will lose additional students to the private sector in the years ahead.

My answer:

Spoiler :

Conditonal statement

#3. Freedom of the press is the most important of our constitutionally guaranteed freedoms. Without it, our other freedoms would be immediately threatened. Futhermore, it provides the fulcrum for the advancement of new freedoms.

My answer:

Spoiler :

Argument
Conclusion = Freedom of the press is the most important of our constitutionally guaranteed freedoms.

#5. It is strongly recommended that you have your house insprected for termite damage at the earliest possible opportunity.

My answer:

Spoiler :

Piece of advice
Though "warning" may be a fair answer too.

#6. Shut the cage door you fool! The lions are escaping into the streets!

My answer:

Spoiler :

Warning

#11. In every insurance contract there is an implied covenant of good faith and fair dealing. The duty to so act is imminent in the contract whether the company is attending to the claims of third persons against the insured or the claims of the insured itself. Accordingly, when the insurer unreasonably and in bad faith withholds payment of the claim of its insured, it is subject to liability in tort.
(Justice Sullivan, Gruenberg v. Aetna Insurance Co.)

My answer:

Spoiler :

Expository passage

#14. Israeli doctors have discovered that nations first known heterosexual transmission of the AIDs virus. The Jerusalem Post said the wife of a drug addict tested positive for the antibodies of the virus. Since the woman is not a drug addict or the recipient of a blood transfusion, she probably was infected through heterosexual rerlations with her husband, doctors said.
(Newspaper clipping)

My answer:

Spoiler :

Report - if we are only taking into consideration the fact that it's a newspaper clipping.
or
argument - if we take into consideration what the doctors' are arguing.

#17. Young people at universities study to achieve knowledge and not to learn a trade. We must all learn how to support ourselves, but we must also learn how to live. We need a lot of engineers in the modern world but we do not want a world of modern engineers.
(Winston Churchill, A Churchill Reader, ed. Colin R. Coote)

Your turn to answer this one...

#20 Since the time of the ancient Greeks, two distinct types of motion have seemed central to an understanding of the universe: the motion of the celestial bodies and the motion of objects on earth. These two kinds of motion were considered as separate matters until the works of Galileo and Newton.
(Douglas C. GIancoli, The Ideas of Physics)

My answer:

Spoiler :

Report

​

And now for something a bit more fun. This exercise consists of a number of selections from letters to the editor of various newspapers and magazines compiled in our text book. Our job is to figure out which ones give good reason to be considered arguments and identify the conclusion.

#2. At the risk of proselytizing for vegetarianism and thus invoking the wrath of my fellow mad-for-meat texans, I must add one observation of my own. Meat eating is not only hypocritical, it is immoral. Many if not most of the world's people are starving. It has been estimated that for every pound of meat protein consumed, approximately 20 pounds of vegetable protein are lost, having been consumed by the animal that is later converedted into meat.
(James M. Martin)

My answer:

Spoiler :

Argument
conclusion is: Meat eating is not only hypocritical, it is immoral.

#3. Shelters and the relocation of city populations are outmoded concepts, suitable only for the more limited wars of the past rather than the international extinction our world leaders have been preparing. Civil "defense" goals should be directed toward moving our millions of citizens promptly into the most likely target areas so that transition into a possible next dimension will take the fewest possible seconds.
(Evan Lodge)

My answer:

Spoiler :

Not an argument

#6. American think more of their automibiles than they do of educating their children. When I had my car serviced the other day, I saw a sign that said the labor charge for working on an automobile is $34 an hour. If teachers were paid this much, they would make $54,400 a year. This is about twice what the highest paid teacher in Los Angeles earns.
(Walter O. Harris)

Your turn to answer...

​

 

[lovett]

Whereas an argument is intended to prove something, non-arguments are not.

I don't like this at all.

Hurley seems to be introducing intentionality into logic (if your interpretation is correct). He is saying that we can know if something is an argument, and thereby amenable to the tools of logical calculi, only if we know things about the mental state of the utterer. Precisely, some set of propositions is an argument if and only if the utterer intends to deduce something from that set of propositions.

This is problematic. It is possible that one does not intend to deduce something when one writes a conditional statement. We can imagine individuals with non-standard mental lives like this, and we have such lives precisely if we are writing absentmindedly. If I write 'P, P->Q |- Q' without thinking I can hardly be said to have attempted to deduce (or 'prove') 'Q' (I wasn't thinking!), but P, P->Q |- Q is still an argument.

We can also imagine that I do intend to deduce things from non-arguments. I could say 'Don't close the door!' and intend to deduce 'Don't open the door!' but that doesn't make these two imperatives into an argument. They remain simply imperatives. That I intend an imperative to be an argument don't make it so.

Intentionality has no place, that I can see, in logic. Arguments are valid or invalid, sound or unsound regardless of human intentions. Human intentions are contingent things, contingent on human beings. Logical truths are necessary. They do not depend on contingent facts about human nature. Or, if they do, there is simply no such thing as 'logic'.

So Hurley is wrong to go down this path. Indeed, there is little real need to distinguish arguments from non-arguments in logic. It is better to just consider as an argument any set of propositions. By the lights of logicians, some perfectly assertable sets will be either unsound or invalid. But I do not see how that matters much; human language is used for things other than meeting the validity or soundness conditions of logic.

Anyway, I hope you enjoy studying logic.

 

[Gary Childress]

I don't like this at all.

Hurley seems to be introducing intentionality into logic (if your interpretation is correct). He is saying that we can know if something is an argument, and thereby amenable to the tools of logical calculi, only if we know things about the mental state of the utterer. Precisely, some set of propositions is an argument if and only if the utterer intends to deduce something from that set of propositions.

This is problematic. It is possible that one does not intend to deduce something when one writes a conditional statement. We can imagine individuals with non-standard mental lives like this, and we have such lives precisely if we are writing absentmindedly. If I write 'P, P->Q |- Q' without thinking I can hardly be said to have attempted to deduce (or 'prove') 'Q' (I wasn't thinking!), but P, P->Q |- Q is still an argument.

We can also imagine that I do intend to deduce things from non-arguments. I could say 'Don't close the door!' and intend to deduce 'Don't open the door!' but that doesn't make these two imperatives into an argument. They remain simply imperatives. That I intend an imperative to be an argument don't make it so.

Intentionality has no place, that I can see, in logic. Arguments are valid or invalid, sound or unsound regardless of human intentions. Human intentions are contingent things, contingent on human beings. Logical truths are necessary. They do not depend on contingent facts about human nature. Or, if they do, there is simply no such thing as 'logic'.

So Hurley is wrong to go down this path. Indeed, there is little real need to distinguish arguments from non-arguments in logic. It is better to just consider as an argument any set of propositions. By the lights of logicians, some perfectly assertable sets will be either unsound or invalid. But I do not see how that matters much; human language is used for things other than meeting the validity or soundness conditions of logic.

Anyway, I hope you enjoy studying logic.

My apologies. The quote cited above is in my own words. Perhaps I summarized incorrectly or tried to be too brief. The book states the following:

"Not all passages contain arguments. Because logic deals with arguments, it is important to be able to distinguish passages that contain arguments from those that do not. In general, a passage contains an argument if it purports [my emphasis] to prove something; if it does not do so, it does not contain an argument. Two conditions must be fulfilled for a passage to purport to prove something.

1. At least one of the statements in the passage must present evidence (or reasons for something).
2. There must be a claim that the evidence (or reasons) supports something."​

How does that sound? Better? Not so much better? If not better then what do you think would be a better statement?

 

[Global Skeptic]

"Now "why a thing is itself" is a meaningless inquiry (for—to give meaning to the question 'why'—the fact or the existence of the thing must already be evident—e.g., that the moon is eclipsed—but the fact that a thing is itself is the single reason and the single cause to be given in answer to all such questions as why the man is man, or the musician musical, unless one were to answer, 'because each thing is inseparable from itself, and its being one just meant this.' This, however, is common to all things and is a short and easy way with the question.)" - Metaphysics, Book VII, Part 17

"The same attribute cannot at the same time belong and not belong to the same subject and in the same respect." - Metaphysics G, 3,1005b18-20)

It is impossible, then, that 'being a man' should mean precisely not being a man, if 'man' not only signifies something about one subject but also has one significance. … And it will not be possible to be and not to be the same thing, except in virtue of an ambiguity, just as if one whom we call 'man', and others were to call 'not-man'; but the point in question is not this, whether the same thing can at the same time be and not be a man in name, but whether it can be in fact. (Metaphysics 4.4, W.D. Ross (trans.), GBWW 8, 525–526).

• the law of identity (A=A)
• the law of non-contradiction (A does not equal ~A)
• and the law of the excluded middle (either A or not A but not both A and ~A)

So in what senses/respects are these laws universal, absolute and relative?
What happens if we use them on everything, something, something else and/or nothing?