# PART III - Symbolic Logic Chapter 7 - Sentential Propositions

Size: px
Start display at page:

Transcription

1 Logic: A Brief Introduction Ronald L. Hall, Stetson University 7.1 Introduction PART III - Symbolic Logic Chapter 7 - Sentential Propositions What has been made abundantly clear in the previous discussion of categorical logic is that there are often trying challenges and sometimes even insurmountable difficulties in translating arguments in ordinary language into standard-form categorical syllogisms. Yet in order to apply the techniques of assessment available in categorical logic, such translations are absolutely necessary. These challenges and difficulties of translation must certainly be reckoned as limitations of this system of logical analysis. At the same time, the development of categorical logic made great advances in the study of argumentation insofar as it brought with it a realization that good (valid) reasoning is a matter of form and not content. This reduction of good (valid) reasoning to formal considerations made the assessment of arguments much more manageable than it was when each and every particular argument had to be assessed. Indeed, in categorical logic this reduction to form yielded, from all of the thousands of possible syllogisms, just fifteen valid syllogistic forms. Taking its cue from this advancement, modern symbolic logic tried to accomplish such a reduction without being hampered with the strict requirements of categorical form. To do this, modern logicians developed what is called sentential logic. As with categorical logic, modern sentential logic reduces the kinds of propositions to a small and thus manageable number. In fact, on the sentential reduction, there are only two basic propositional forms: simple propositions and compound propositions. (Wittgenstein called simple propositions elementary propositions. ) But it would be too easy to think that this is all there is to it. What complicates the sentential formal reduction is that there are a number of different kinds of compound propositions. These different kinds of compound propositions are called propositional forms and are determined by the several different ways that simple propositions can be combined to form compound propositions. Fortunately, there is a small and manageable number of these connections, hence a relatively small number of different compound propositional forms. In this Chapter we will investigate five compound propositional forms. These forms are as follows: 1. Conjunctions 2. Negations 3. Disjunctions 4. Conditionals 5. Biconditionals. This reduction of every compound proposition to one of these forms is almost as neat as the categorical reduction to the four standard-form categorical propositions, A, E, I, O. However, the flexibility and power of the sentential system of logic, as we will see, is much greater than we had in categorical logic. For one thing, in sentential logic there is no necessity for reformulating arguments as standard-form syllogisms. Chapter 7 p.1

2 There is no better way to see the flexibility and power of the sentential system of symbolic logic than to jump right into an explanation of these five kinds of compound propositional forms. Before we do this, however, we need to say something more about the basic distinction between simple and compound sentential propositions. A good place to start is with some definitions. So we will define the two as follows: Simple Proposition: An assertion (either true or false) that cannot be broken down into a simpler assertion. Example: The cat is on the mat. Compound Proposition: An assertion of a combination of simple propositions Example: The cat is on the mat and the dog is in the yard. Compound propositions are like simple propositions insofar as they are either true or false. However, the truth or falsity of a compound proposition is a function of the truth or falsity of its component simple propositions. Because this is so, sentential logic is sometimes called truth-functional logic. All this means is that the truth or falsity of a compound proposition is determined by the truth-values of its component simple propositions. I will say more as to how this determination is made as we proceed. Sentential logic has adopted the convention of using upper case letters to stand for particular simple propositions. So in this system, C can be used to stand for the simple proposition, The cat is on the mat. It is common practice to use a letter that reminds us of the content of the particular proposition that we are symbolizing, but we are free to use any letter we choose. We use C because it reminds us of cat. To symbolize a compound proposition, we simply join more than one simple proposition together, symbolizing each simple proposition with an upper case letter. So, to symbolize the compound proposition, The cat is on the mat and the dog is in the yard we simply substitute the following symbolic expression: C and D. The and here is called a truth-functional connective. It is called a connective since it connects two or more simple propositions to form the compound proposition. It is said to be a truth-functional connective because the truth-value of the compound proposition that it forms is a function of the truth-values of its component simple propositions. One way to characterize the 5 kinds of compound propositional forms that we are now going to look at is to say that they represent 5 different truth-functional connectives, that is, 5 different ways to combine simple propositions into compound ones. The name of each of these several kinds of compound propositional forms is determined by the kind of the truth-functional connective that forms it. Enough said then by way of introduction. Let s turn to our first kind of truth-functional connective and accordingly to the first kind of propositional form, namely, the conjunction. 7.2 The Conjunction Usually conjunctions are formed by joining two or more simple propositions together with the word and. This word and has a function and that function is to join two or more simple propositions together to form a compound proposition known as a conjunction. The simple propositions that are joined together to form a conjunction are called conjuncts. The word and in English is not the only word that can have this function. Other English words, as well as grammatical techniques, can be surrogates for and and serve to function exactly as it does. Such surrogates include but, nevertheless, moreover, however, yet, also, and others, and sometimes simply a comma or semicolon. For example, it is clearly the case that the compound proposition, The cat is on the mat and the dog Chapter 7 p.2

3 is in the yard, has exactly the same sense, reference, and truth-value as the compound proposition, The cat is on the mat but the dog is in the yard, or as the proposition, The cat is on the mat; the dog is in the yard. As well, sometimes and, does not serve this function of conjoining two or more propositions together to forma conjunction. For example, Two and Two makes four. Should not be seen as a compound proposition. Even though we have the word and in this sentence, it is not functioning to join two or more simple propositions together. To capture and express the function of and, we will adopt the following symbol " " (the dot) to stand for this truth-functional connective. Using this symbol, we can express symbolically the proposition, The cat is on the mat and the dog is in the yard as follows: C D. This expression is a conjunction with two simple conjuncts C and D. The symbol expresses the and function whether or not the word and is used, but only when that function is intended in the expression that is being symbolized. The symbol for "and" is a truth-functional connective, insofar as the truth-value of the compound proposition it forms is a function of the truth-values of its component simple conjuncts. We must rely here on our ear for what makes a given compound proposition true or false. Clearly, we would all agree, common usage, tells us that the proposition, The cat is on the mat and the dog is in the yard is false if either the cat is on not the mat or the dog is not in the yard, or both. So there we have it. All we have to do is formalize and generalize this agreement in use. We do this by saying that any is true if and only if both conjuncts (the p and the q ) are true, and is false otherwise. So far so good. However, as we have been finding out, ordinary language does not always oblige our attempts to reduce it to symbolic forms. Certainly, it is obvious that many expressions of conjunctions in ordinary language are not confined to such straightforward conjunctions with just two conjuncts. For example, the following sentence is clearly a conjunction of sorts: The cat is on the mat, the dog is in the yard, and the sheep are in the meadow. This is a conjunction, but it has three conjuncts. How then do we determine its truth-value? We cannot as this proposition now stands. We need some clarification in logic that is similar to the clarification provided in ordinary language by punctuation marks. With some punctuation marks, we will be able to see that our conjunction can be expressed in the standard form in which it has two conjuncts, a right and a left conjunct The punctuation that has been adopted in sentential logic is as follows: parentheses ( ); brackets [ ]; braces { }. By convention, we use parentheses up to three times before we turn to brackets and then to braces. To see how this works, let s go back to our conjunction with three conjuncts. That proposition could be symbolically expressed as follows: C D S As stated, we cannot readily see how this fits the standard form of a conjunction in which the conjunction has just two conjuncts. However, if we punctuate the given proposition, it will be clear that the proposition is in standard form. To do this, we must reduce our proposition with three conjuncts to a proposition with only two conjuncts. We can do this, in two equally legitimate ways, as follows: (C D) S or C (D S). Both of these ways of punctuating the conjunctions are equally legitimate since the trut -value of either rendering remains unchanged. Every standard form conjunction has just two conjuncts. This procedure applies to any conjunction regardless of how many conjuncts it might have. We know that we have gotten our punctuation correct when we can see that the symbol for "and" clearly divides two sides of the conjunction, the p side and the q side. When this is done, we have reduced the number of conjuncts to two. The symbol for "and" that marks this divide is called the main truth-functional connective. As we will explain momentarily, the main truth functional connective determines the kind of compound proposition we have and hence the conditions under which that proposition is either true or false. Chapter 7 p.3

4 It may be helpful to define the truth conditions of p q with the following table. Certainly, the table makes it clear that the only time that any conjunction whatsoever is true is when both of its conjuncts are true, and itis false otherwise. P Q P Q T T T T F F F T F F F F 7.3 The Negation The second kind of compound proposition the negation is formed by using a truth-functional connective, also known as negation. What and is to conjunction, not is to negation. Again, these connectives designate a function that these terms have, namely, the function of forming connections between and among other propositions. And like the case with and, there are surrogates for not, including it is false that, it is not the case that, and others. We will use ~ (the curl) as our symbol for not. Accordingly, the propositional form of negation can be symbolized as follows: ~ p. Here this ~ p stands for the negation of any proposition whatsoever, compound or simple. To negate a proposition is just to assert that that proposition is not true. However, we can also assert that it is not true that some proposition is false. To make this assertion is to assert something that is true. For example, to say "It is false that the cat is on the mat" is to assert something true if the cat is not in fact on the mat." As well, double negations cancel themselves out as follows ~ ~ p is equivalent to p. In general, the symbol for "not" functions as a negation of the truth-value of whatever proposition it ranges over. The negation of a false proposition produces a true one, the negation of a true proposition produces a false one, and double negations cancel each other out. This means that if a proposition is modified by three negation signs two of them can be eliminated without affecting the truth-value of the original as follows: ~ ~ ~ p is equivalent to ~ p. If we want to express symbolically the assertion that The cat is not on the mat, is false, we can do so with the expression ~ C. If C is true, then ~ C is false. Regardless of the truth-value of C, the expression ~ C is a well-formed negation since it is a substitution instance of the propositional form for negation, namely, ~ p. Recall, that the p in ~ p can stand for any proposition whatsoever. As such, the symbol for negation negates, or denies, or otherwise asserts that the truth-value the proposition p is negated. Let s go back to our discussion of conjunctions to see how negation works in relation to other compound propositions. A curl (~) can negate a simple or a compound proposition. Consider the conjunction, C D. The curl can negate this conjunction. But we must be careful. ~(C D) is not the same as ~ C ~ D. The curl negates what it modifies. What this symbolic expression asserts is that It is false that the cat is on the mat and the dog is in the yard. Adding the parenthesis as punctuation here, is critical, for it makes it clear that the not ranges over the whole conjunction and not over each conjunct. That is, what is denied here is the conjunction. And again, this is very different from denying each of the conjuncts, which we could also express, but with a different symbolic representation. To express the claim that the cat is not on the mat and the dog is not in the yard, our symbolic representation would be as follows: ~ C ~ D. If the distinction between denying a conjunction and denying both conjuncts is not clear, try this: let L stand for the proposition Abraham Lincoln was elected President and D stand for the proposition, Stephen Douglas was elected. Clearly, it is false that both were elected; that is, the denial of the conjunction is a true Chapter 7 p.4

5 assertion. Just as clearly, it is a false assertion if we were to say that it is false that Lincoln was elected and it is false that Douglas was elected, since Lincoln was in fact elected. When we examine the two propositions ~ (L D), and ~ L ~ D, we see that they are different kinds of compound propositions. We see this by recognizing that they have different main truth-functional connectives. The main truth-functional connective in the first proposition is the symbol for negation and hence the first proposition is a negation. The main truth-functional connective in the second expression is the symbol for "and making it a conjunction. This is very important to notice because the truth conditions for a conjunction are different from the truth conditions of a negation. The process of finding the truth-value of proposition ~ L ~ D is quite different from determining the truth- value of ~ (L D). A conjunction is true if and only if both of its conjuncts are true. In this case, L is true (Lincoln was elected) and hence ~ L" is false. And even though the other conjunct ~ D is true because D, which is false (Douglas was not elected), is negated, making it true, a true conjunction must have both of its conjuncts be true if it is to be true. Hence, under this interpretation of L and D, ~ L ~ D is false, and hence the two propositions ~ (L D) and ~ L ~ D do not make the same assertion. Not both is not the same assertion as both are not. We must be careful not to confuse these expressions. 7.4 The Disjunction The third kind of compound proposition we will consider is the disjunction. A disjunction is an either/or propositions. Although it may sound strange to you, when we connect two propositions with unless, the preferred translation yields a disjunction, an either/or proposition. For example, the best translation of The cat is on the mat, unless the dog is in the yard is either C or D. We will use v (the wedge) as our symbol for the truth-functional connective either/or. Accordingly, the either/or proposition, Either the cat is on the mat or the dog is in the yard is symbolized as follows: C v D. The two parts, the either part and the or part, of any disjunction (the C and the D ) are called disjuncts. Every standard form disjunction has two disjuncts. When we are trying to translate sentences in ordinary language into symbolic sentential form, we will have to use the proper punctuation. For example, suppose I am trying to represent the following English sentence symbolically: Either Bill and Sarah won scholarships or both did not win scholarships. Clearly this compound proposition has an either/or structure. However, it also seems to involve two conjunctions and negations. The tokens of the conjunctions here are and and both; the token of the negations is not. On careful inspection, we notice that the and occurs in the either disjunct and that the both occurs in the or disjunct. We also notice the token of the negations occurs in the or disjunct. This leads us to see that this proposition is a disjunction of two conjunctions. We express it as follows: (B S) v (~ B ~ S). Clearly, the main truth-functional connective in this proposition is the symbol for disjunction and this is sufficient to determine that this compound proposition is a disjunction and not, say, a conjunction, or a negation. In this disjunction, the left disjunct is a conjunction of two simple propositions and the right disjunct is a conjunction of two negated simple propositions. (Make sure you do not think of the right disjunct here as a negation. It is not. Nevertheless, it does involve two negations, namely, ~B and ~ S. ) The truth-value of the compound disjunctive assertion is a function of the truth-values of its component disjuncts. Again, we can rely on common usage to help us, at least part of the way, in making this determination. Clearly, if both disjuncts in a disjunction are false, the entire disjunction is false. And it seems just as clearly the case that if either disjunct in a disjunction is true the compound assertion is also true. We may not be so sure what to say, however, about the last possibility here, namely, we are not so sure what to say about the truth-value of a disjunction both of whose disjuncts are true. Chapter 7 p.5

6 It is natural that we should wonder about this, since there is an ambiguity in the way that we use either/or sentences in ordinary language. Suppose that someone says, I am either going to law school or to medical school. Let s also suppose that the person goes to law school, drops out, and goes to medical school. Do we want to say that what he or she said originally turned out to be false? It seems not. On the other hand, suppose someone says, I am either going to marry or remain a bachelor. Now it looks like this person cannot do both. And in many other ordinary circumstances, when one says, I will go to the movies or to the races, he or she usually means one or the other but not both. These two senses of disjunction are called its inclusive and its exclusive senses. In the inclusive sense, an either/or proposition is true if both of its disjuncts are true, and in the exclusive sense, an either/or proposition is false if both of its disjunctions are true. So are we going to interpret disjunctions as inclusive or as exclusive? Can we do both? Or must we do one or the other? Well the fact is we need to acknowledge both senses of either/or expressions. But, we can do this by taking the inclusive sense of disjunction as basic. This is because the exclusive sense of either/or is actually best expressed as a conjunction. What the exclusive disjunction asserts is something like this: P or Q and not both P and Q. More symbolically, the exclusive disjunction can be expressed as the following conjunction: (P v Q) ~ (P Q) If the sense of the sentence that we are translating seems to require the exclusive sense of disjunction we can express this with a proposition in the form of this conjunction. Otherwise, we simply take either/or sentences to find their most basic translation as inclusive disjunctions. What this means is that the truth conditions for a disjunction are as follows: A disjunction is true if and only if either or both of its disjuncts are true and false if and only if both disjuncts are false. We can depict these truthconditions as follows: P Q P v Q T T T T F T F T T F F F Before we move on, we need to consider one other issue, what we might call the negative cousins of either/or" propositions, that is, neither/nor propositions. These expressions can be expressed in the following symbolic form: ~ (P v Q). If one says: I am neither going to law school nor to medical school, the sense of this assertion is that this person is not going to law school and this person is not going to medical school. As such this neither/nor expression is logically equivalent to the conjunction of two negated simple propositions. In other words, this assertion about law school and medical school can be symbolized as follows: ~ L ~ M. But this is logically equivalent to the expression ~ (L v M) since the only condition in which this assertion ~ (L v M) could be true is for L v M to be false; and the only way that L v M can be false is when L is false and M is false. In summary, then, neither/nor expressions can be expressed as ~ (P v Q), or as ~ P ~ Q. We must let the sense of the English sentence we are translating dictate which translation is appropriate. 7.5 The Conditional The fourth kind of compound propositional form we will consider is the conditional (sometimes called the hypothetical). Propositions of this form use if/then (or a surrogate expression, like only if ) as their truthfunctional connective. For example, the following two propositions are instances of this form: If the cat is on the mat, then the dog is in the yard, and The cat is on the mat, only if the dog is in the yard. Chapter 7 p.6

7 We will use " " (we call this the horseshoe) as our symbol for the truth-functional connective if/then. Accordingly, the if/then proposition, If the cat is on the mat, then the dog is in the yard is symbolized as follows: C D. The two parts of any conditional proposition have names: the if part is called the antecedent and the then part is called the consequent. When we are translating sentences in ordinary language into symbolic sentential form, we will have to use the proper punctuation. For example, suppose I am trying to represent the following English sentence symbolically: If Bill and Sarah won scholarships, then Joe and Mary did not win scholarships. Clearly, this compound proposition has an if/then structure. However, it also seems to involve a conjunction and negations. On careful inspection, we notice that the and occurs in both the antecedent and in the consequent of this conditional proposition. We also notice that there are two negations in the consequent. This leads us to see that this proposition is a conditional whose antecedent is a conjunction of two simple propositions and whose consequent is a conjunction of two negated simple propositions. We express it as follows: (B S) (~J ~ M). Clearly, the main truth-functional connective is the symbol for "If/then" and this is sufficient to determine that this compound proposition is a conditional proposition and not, say, a conjunction, or a negation. In this conditional proposition, the antecedent is a conjunction of two simple propositions and the consequent is a conjunction of two negated simple propositions. (Again, make sure you do not think of the consequent as a negation. It is not. However, it does involve two negations, namely, ~ J and ~ M ). One important way to characterize the relation between the antecedent and the consequent of a conditional proposition is to say that the antecedent represents the sufficient condition in the conditional relation and the consequent represents the necessary condition in that relation. For example, we know that oxygen is the necessary condition for the presence of fire, and that fire is a sufficient condition for the presence of oxygen. We can express this relation symbolically in the following conditional proposition: F O. This proposition asserts that O is the necessary condition for F and that F is the sufficient condition for O. More generally, we say that the antecedent always expresses the sufficient condition and the consequent always expresses the necessary condition in a conditional (if/then) relationship. One more helpful reminder: When if occurs in a sentence, it is a good policy to take what it ranges over as the sufficient condition in a conditional relation. In addition, when we find only if or only it is a good policy to take what these words range over to be the necessary condition in a conditional relation. Consider the following example: Only women are allowed. Here being a woman is the necessary condition for being allowed. Therefore, we would symbolize this as, A W. Now consider the difference between the following two propositions: You can go the fair only if you do your homework, and You can go to the fair if you do your homework. In the first case, doing homework is set as the necessary condition for going to the fair; in the second, doing homework is set as the sufficient condition for going to the fair. Accordingly, the first sentence is symbolized as F H, and the second is symbolized as H F. Now we must ask what the truth conditions are in conditional propositions. Remember this compound proposition, like all of those we will consider here, is truth-functional. That is, the truth-value of the compound conditional proposition is a function of the truth-values of its component parts, its antecedent and its consequent. Again, we can rely on intuition to help us, but only to some degree; indeed, we might come to some conclusions that seem to be counter-intuitive. The reason for this is that there are so many senses of the if/then proposition as it is ordinarily used. Consider the following example of an ordinary use of an if/then assertion. If this figure is a triangle, then this figure has only three sides. This is what we might call an analytic or a logical sense of if/then. We could symbolize this as follows: T S. (T= "this figure is a triangle"; S= "this figure has only three sides.") Clearly if T is true, it is logically impossible for S to be false. As such, this proposition asserts a relation between T and S that is stronger than other possible uses of if/then assertions. Chapter 7 p.7

8 We sometimes use conditional propositions in such a way that it is possible for the antecedent and the consequent to have different truth-values and nevertheless be true. Consider this proposition: If I go to the movies, then I will see Jane ( M J ). Suppose that the antecedent of this proposition is false, would the consequent also have to be false in order for this conditional assertion to be true? Surely not. Indeed, if J is true (I do see Jane), and if M is false (I do not go to the movies) the conditional proposition could still be true. As well, we sometimes use if/then assertions in a causal sense. For example, the following proposition asserts such a causal relation: If I turn the light switch to the on position, then the lights will immediately come on. We might symbolize this proposition as follows: T O. The relation between T (turning the switch to the on position) and O (the lights immediately coming on) is not a logical relation but a physical one. Suppose that as a matter of fact I turn the switch to the on position and it just so happens that the lights do immediately come on, that is, suppose that both T and O are true, is the conditional proposition T O true? Well, if it so happens that there is no physical connection between the switch and the lights (they are controlled actually by a photoelectric sensor), we would likely say that the conditional is false. In this case, the antecedent and the consequent are true but the conditional proposition is false. And there are other senses of if/then in our ordinary usages. So which of these is the most basic? If the conditional proposition is to be treated as a truth-functional proposition, we must say how the truth of the entire if/then proposition is a function of the truth of its components, that is, its antecedent and its consequent. As it happens, logicians have agreed that what a conditional proposition asserts most basically is logically equivalent to the following two propositions: (~ p v q) and ~ (p ~q). This reading of the if/then does seem to capture a basic sense. Consider an ordinary assertion such as, If I go to the movies then I will see Jane. This is equivalent to saying, Either I do not go to the movies or I will see Jane, and It is false that I go to the movies and do not see Jane. To interpret an if/then proposition in this basic sense is to interpret it as asserting what logicians call a conditional relation of material implication. Since we have already established the truth conditions for the disjunction and negation, and since we are adopting as basic the sense of an if/then proposition as what is captured in the logically equivalent expression ~p v q, or ~ (p ~q) we can now establish the truth-conditions for the conditional. The following table should show this clearly: P Q ~ P v Q ~ (P ~Q) P Q T T T T T T F F F F F T T T T F F T T T In summary, what this means is that the truth conditions for a conditional are as follows: a conditional proposition is false if and only if its antecedent is true and its consequent is false, and it is true in every other case. The truth conditions for a conditional proposition will have important implications, as we will soon learn. I also must note that the truth conditions for the conditional carries a consequent that may strike you as a bit odd. If the antecedent of a conditional opposition is false, the proposition is true regardless of the truth-value of the consequent. Propositions with a false antecedent are counterfactual propositions. In these cases, no matter what the consequent is, even if obviously false, the conditional proposition is true. For example, If I jump out of the window, I will become a butterfly is true if it is false that I have jumped out of the window (~ J v B). Clearly if I do not jump out of the window, that is if ~ J is true then (~ J v B) must be true. Remember that one true disjunct Chapter 7 p.8

9 is sufficient to make the disjunction true, whether B is true or false. We will just have to put up with such logical consequences of reading conditional propositions as material conditionals. 7.6 The Biconditional The fifth kind of compound propositional form we will consider is the biconditional. Propositions of this form use if and only if (or a surrogate expression, like necessary and sufficient ) as their truth-functional connective. For example, the following two propositions are biconditionals: The cat is on the mat if and only if the dog is in the yard, and The cat is on the mat is the necessary and sufficient condition for the dog s being in the yard. We will use " " (the triple bar) as our symbol for the truth-functional connective if and only if. Accordingly, the if and only if proposition, The cat is on the mat if and only if the dog is in the yard is symbolized as follows: C D. When we translate sentences in ordinary language into symbolic sentential form, we will have to use the proper punctuation. For example, suppose I am trying to represent the following English sentence symbolically: Bill and Sarah won scholarships if and only if Joe and Mary won scholarships. Clearly this compound proposition has an if and only if structure. However, it also involves conjunctions and negations. To make it clear that the biconditional is the main truth-functional connective, we express it as follows: (B S) (~ J ~ M) Now we must ask: what are the truth conditions of a biconditional proposition? Remember this compound proposition, like all of those considered here, is truth-functional. That is, the truth-value of the compound biconditional assertion is a function of the truth-values of its component elements. All we have to do to establish the truth conditions of the biconditional is to recognize that C D is equivalent to either of the following two propositions: (C D) (D C) (C D) v (~C ~D). To interpret an if and only if proposition in this sense is to interpret it as asserting what logicians call a relation of material equivalence. The following table should show this clearly and establish that biconditionals are true only if they have the same truth-values, and false if they have different truth values. Biconditionals are true if both sides are true and if both sides are false and biconditionals are false only if the two sides of the triple bar have different truth-values. P Q (P Q) (Q P) (P Q) v (~P ~ Q) P Q T T T T T T F F F F F T F F F F F T T T Chapter 7 p.9

### Logic: A Brief Introduction

Logic: A Brief Introduction Ronald L. Hall, Stetson University PART III - Symbolic Logic Chapter 7 - Sentential Propositions 7.1 Introduction What has been made abundantly clear in the previous discussion

### Chapter 8 - Sentential Truth Tables and Argument Forms

Logic: A Brief Introduction Ronald L. Hall Stetson University Chapter 8 - Sentential ruth ables and Argument orms 8.1 Introduction he truth-value of a given truth-functional compound proposition depends

### Chapter 9- Sentential Proofs

Logic: A Brief Introduction Ronald L. Hall, Stetson University Chapter 9- Sentential roofs 9.1 Introduction So far we have introduced three ways of assessing the validity of truth-functional arguments.

### What are Truth-Tables and What Are They For?

PY114: Work Obscenely Hard Week 9 (Meeting 7) 30 November, 2010 What are Truth-Tables and What Are They For? 0. Business Matters: The last marked homework of term will be due on Monday, 6 December, at

### Workbook Unit 3: Symbolizations

Workbook Unit 3: Symbolizations 1. Overview 2 2. Symbolization as an Art and as a Skill 3 3. A Variety of Symbolization Tricks 15 3.1. n-place Conjunctions and Disjunctions 15 3.2. Neither nor, Not both

### A BRIEF INTRODUCTION TO LOGIC FOR METAPHYSICIANS

A BRIEF INTRODUCTION TO LOGIC FOR METAPHYSICIANS 0. Logic, Probability, and Formal Structure Logic is often divided into two distinct areas, inductive logic and deductive logic. Inductive logic is concerned

### Symbolic Logic. 8.1 Modern Logic and Its Symbolic Language

M08_COPI1396_13_SE_C08.QXD 10/16/07 9:19 PM Page 315 Symbolic Logic 8 8.1 Modern Logic and Its Symbolic Language 8.2 The Symbols for Conjunction, Negation, and Disjunction 8.3 Conditional Statements and

### Chapter 2 Analyzing Arguments

Logic: A Brief Introduction Ronald L. Hall, Stetson University Chapter 2 Analyzing Arguments 2.1 Introduction Now that we have gotten our "mental muscles" warmed up, let's see how well we can put our newly

### LOGIC ANTHONY KAPOLKA FYF 101-9/3/2010

LOGIC ANTHONY KAPOLKA FYF 101-9/3/2010 LIBERALLY EDUCATED PEOPLE......RESPECT RIGOR NOT SO MUCH FOR ITS OWN SAKE BUT AS A WAY OF SEEKING TRUTH. LOGIC PUZZLE COOPER IS MURDERED. 3 SUSPECTS: SMITH, JONES,

### Logic Appendix: More detailed instruction in deductive logic

Logic Appendix: More detailed instruction in deductive logic Standardizing and Diagramming In Reason and the Balance we have taken the approach of using a simple outline to standardize short arguments,

### Today s Lecture 1/28/10

Chapter 7.1! Symbolizing English Arguments! 5 Important Logical Operators!The Main Logical Operator Today s Lecture 1/28/10 Quiz State from memory (closed book and notes) the five famous valid forms and

### INTERMEDIATE LOGIC Glossary of key terms

1 GLOSSARY INTERMEDIATE LOGIC BY JAMES B. NANCE INTERMEDIATE LOGIC Glossary of key terms This glossary includes terms that are defined in the text in the lesson and on the page noted. It does not include

### ILLOCUTIONARY ORIGINS OF FAMILIAR LOGICAL OPERATORS

ILLOCUTIONARY ORIGINS OF FAMILIAR LOGICAL OPERATORS 1. ACTS OF USING LANGUAGE Illocutionary logic is the logic of speech acts, or language acts. Systems of illocutionary logic have both an ontological,

### Logic: A Brief Introduction. Ronald L. Hall, Stetson University

Logic: A Brief Introduction Ronald L. Hall, Stetson University 2012 CONTENTS Part I Critical Thinking Chapter 1 Basic Training 1.1 Introduction 1.2 Logic, Propositions and Arguments 1.3 Deduction and Induction

### 9 Methods of Deduction

M09_COPI1396_13_SE_C09.QXD 10/19/07 3:46 AM Page 372 9 Methods of Deduction 9.1 Formal Proof of Validity 9.2 The Elementary Valid Argument Forms 9.3 Formal Proofs of Validity Exhibited 9.4 Constructing

### Logic & Proofs. Chapter 3 Content. Sentential Logic Semantics. Contents: Studying this chapter will enable you to:

Sentential Logic Semantics Contents: Truth-Value Assignments and Truth-Functions Truth-Value Assignments Truth-Functions Introduction to the TruthLab Truth-Definition Logical Notions Truth-Trees Studying

### A. Problem set #3 it has been posted and is due Tuesday, 15 November

Lecture 9: Propositional Logic I Philosophy 130 1 & 3 November 2016 O Rourke & Gibson I. Administrative A. Problem set #3 it has been posted and is due Tuesday, 15 November B. I am working on the group

### KRISHNA KANTA HANDIQUI STATE OPEN UNIVERSITY Patgaon, Ranigate, Guwahati SEMESTER: 1 PHILOSOPHY PAPER : 1 LOGIC: 1 BLOCK: 2

GPH S1 01 KRISHNA KANTA HANDIQUI STATE OPEN UNIVERSITY Patgaon, Ranigate, Guwahati-781017 SEMESTER: 1 PHILOSOPHY PAPER : 1 LOGIC: 1 BLOCK: 2 CONTENTS UNIT 6 : Modern analysis of proposition UNIT 7 : Square

### Study Guides. Chapter 1 - Basic Training

Study Guides Chapter 1 - Basic Training Argument: A group of propositions is an argument when one or more of the propositions in the group is/are used to give evidence (or if you like, reasons, or grounds)

### Selections from Aristotle s Prior Analytics 41a21 41b5

Lesson Seventeen The Conditional Syllogism Selections from Aristotle s Prior Analytics 41a21 41b5 It is clear then that the ostensive syllogisms are effected by means of the aforesaid figures; these considerations

### An Introduction to. Formal Logic. Second edition. Peter Smith, February 27, 2019

An Introduction to Formal Logic Second edition Peter Smith February 27, 2019 Peter Smith 2018. Not for re-posting or re-circulation. Comments and corrections please to ps218 at cam dot ac dot uk 1 What

3. Negations 3.1. Not: contradicting content 3.1.0. Overview In this chapter, we direct our attention to negation, the second of the logical forms we will consider. 3.1.1. Connectives Negation is a way

### Illustrating Deduction. A Didactic Sequence for Secondary School

Illustrating Deduction. A Didactic Sequence for Secondary School Francisco Saurí Universitat de València. Dpt. de Lògica i Filosofia de la Ciència Cuerpo de Profesores de Secundaria. IES Vilamarxant (España)

### Instructor s Manual 1

Instructor s Manual 1 PREFACE This instructor s manual will help instructors prepare to teach logic using the 14th edition of Irving M. Copi, Carl Cohen, and Kenneth McMahon s Introduction to Logic. The

### 1.5. Argument Forms: Proving Invalidity

18. If inflation heats up, then interest rates will rise. If interest rates rise, then bond prices will decline. Therefore, if inflation heats up, then bond prices will decline. 19. Statistics reveal that

### Logicola Truth Evaluation Exercises

Logicola Truth Evaluation Exercises The Logicola exercises for Ch. 6.3 concern truth evaluations, and in 6.4 this complicated to include unknown evaluations. I wanted to say a couple of things for those

### Philosophy 1100: Introduction to Ethics. Critical Thinking Lecture 1. Background Material for the Exercise on Validity

Philosophy 1100: Introduction to Ethics Critical Thinking Lecture 1 Background Material for the Exercise on Validity Reasons, Arguments, and the Concept of Validity 1. The Concept of Validity Consider

### Logic: Deductive and Inductive by Carveth Read M.A. CHAPTER IX CHAPTER IX FORMAL CONDITIONS OF MEDIATE INFERENCE

CHAPTER IX CHAPTER IX FORMAL CONDITIONS OF MEDIATE INFERENCE Section 1. A Mediate Inference is a proposition that depends for proof upon two or more other propositions, so connected together by one or

### 2.3. Failed proofs and counterexamples

2.3. Failed proofs and counterexamples 2.3.0. Overview Derivations can also be used to tell when a claim of entailment does not follow from the principles for conjunction. 2.3.1. When enough is enough

### 7.1. Unit. Terms and Propositions. Nature of propositions. Types of proposition. Classification of propositions

Unit 7.1 Terms and Propositions Nature of propositions A proposition is a unit of reasoning or logical thinking. Both premises and conclusion of reasoning are propositions. Since propositions are so important,

### Artificial Intelligence: Valid Arguments and Proof Systems. Prof. Deepak Khemani. Department of Computer Science and Engineering

Artificial Intelligence: Valid Arguments and Proof Systems Prof. Deepak Khemani Department of Computer Science and Engineering Indian Institute of Technology, Madras Module 02 Lecture - 03 So in the last

### Part II: How to Evaluate Deductive Arguments

Part II: How to Evaluate Deductive Arguments Week 4: Propositional Logic and Truth Tables Lecture 4.1: Introduction to deductive logic Deductive arguments = presented as being valid, and successful only

### Chapter 1 - Basic Training

Logic: A Brief Introduction Ronald L. Hall, Stetson University Chapter 1 - Basic Training 1.1 Introduction In this logic course, we are going to be relying on some mental muscles that may need some toning

### An alternative understanding of interpretations: Incompatibility Semantics

An alternative understanding of interpretations: Incompatibility Semantics 1. In traditional (truth-theoretic) semantics, interpretations serve to specify when statements are true and when they are false.

### Moore on External Relations

Moore on External Relations G. J. Mattey Fall, 2005 / Philosophy 156 The Dogma of Internal Relations Moore claims that there is a dogma held by philosophers such as Bradley and Joachim, that all relations

### 2.1 Review. 2.2 Inference and justifications

Applied Logic Lecture 2: Evidence Semantics for Intuitionistic Propositional Logic Formal logic and evidence CS 4860 Fall 2012 Tuesday, August 28, 2012 2.1 Review The purpose of logic is to make reasoning

### Rosen, Discrete Mathematics and Its Applications, 6th edition Extra Examples

Rosen, Discrete Mathematics and Its Applications, 6th edition Extra Examples Section 1.1 Propositional Logic Page references correspond to locations of Extra Examples icons in the textbook. p.2, icon at

### PHILOSOPHY 102 INTRODUCTION TO LOGIC PRACTICE EXAM 1. W# Section (10 or 11) 4. T F The statements that compose a disjunction are called conjuncts.

PHILOSOPHY 102 INTRODUCTION TO LOGIC PRACTICE EXAM 1 W# Section (10 or 11) 1. True or False (5 points) Directions: Circle the letter next to the best answer. 1. T F All true statements are valid. 2. T

### Informalizing Formal Logic

Informalizing Formal Logic Antonis Kakas Department of Computer Science, University of Cyprus, Cyprus antonis@ucy.ac.cy Abstract. This paper discusses how the basic notions of formal logic can be expressed

### 1 Clarion Logic Notes Chapter 4

1 Clarion Logic Notes Chapter 4 Summary Notes These are summary notes so that you can really listen in class and not spend the entire time copying notes. These notes will not substitute for reading the

### MCQ IN TRADITIONAL LOGIC. 1. Logic is the science of A) Thought. B) Beauty. C) Mind. D) Goodness

MCQ IN TRADITIONAL LOGIC FOR PRIVATE REGISTRATION TO BA PHILOSOPHY PROGRAMME 1. Logic is the science of-----------. A) Thought B) Beauty C) Mind D) Goodness 2. Aesthetics is the science of ------------.

### 1.6 Validity and Truth

M01_COPI1396_13_SE_C01.QXD 10/10/07 9:48 PM Page 30 30 CHAPTER 1 Basic Logical Concepts deductive arguments about probabilities themselves, in which the probability of a certain combination of events is

### HANDBOOK. IV. Argument Construction Determine the Ultimate Conclusion Construct the Chain of Reasoning Communicate the Argument 13

1 HANDBOOK TABLE OF CONTENTS I. Argument Recognition 2 II. Argument Analysis 3 1. Identify Important Ideas 3 2. Identify Argumentative Role of These Ideas 4 3. Identify Inferences 5 4. Reconstruct the

### Ayer s linguistic theory of the a priori

Ayer s linguistic theory of the a priori phil 43904 Jeff Speaks December 4, 2007 1 The problem of a priori knowledge....................... 1 2 Necessity and the a priori............................ 2

### (Refer Slide Time 03:00)

Artificial Intelligence Prof. Anupam Basu Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur Lecture - 15 Resolution in FOPL In the last lecture we had discussed about

### Truth At a World for Modal Propositions

Truth At a World for Modal Propositions 1 Introduction Existentialism is a thesis that concerns the ontological status of individual essences and singular propositions. Let us define an individual essence

### Introduction Symbolic Logic

An Introduction to Symbolic Logic Copyright 2006 by Terence Parsons all rights reserved CONTENTS Chapter One Sentential Logic with 'if' and 'not' 1 SYMBOLIC NOTATION 2 MEANINGS OF THE SYMBOLIC NOTATION

### Philosophy 220. Truth Functional Properties Expressed in terms of Consistency

Philosophy 220 Truth Functional Properties Expressed in terms of Consistency The concepts of truth-functional logic: Truth-functional: Truth Falsity Indeterminacy Entailment Validity Equivalence Consistency

### Overview of Today s Lecture

Branden Fitelson Philosophy 12A Notes 1 Overview of Today s Lecture Music: Robin Trower, Daydream (King Biscuit Flower Hour concert, 1977) Administrative Stuff (lots of it) Course Website/Syllabus [i.e.,

### Tutorial A03: Patterns of Valid Arguments By: Jonathan Chan

A03.1 Introduction Tutorial A03: Patterns of Valid Arguments By: With valid arguments, it is impossible to have a false conclusion if the premises are all true. Obviously valid arguments play a very important

### PROPOSITIONAL LOGIC OF SUPPOSITION AND ASSERTION 1

PROPOSITIONAL LOGIC OF SUPPOSITION AND ASSERTION 1 1. LANGUAGE AND SPEECH ACTS In this paper I develop a system of what I understand to be illocutionary logic. In order to motivate this system and make

### Dynamics of change in logic

Philosophical Institute of Czech Academy of Sciences PhDs in Logic, Prague May 2, 2018 Plurality of logics as philosophical problem There are many logical systems, yet it is not clear what this fact tells

### Exposition of Symbolic Logic with Kalish-Montague derivations

An Exposition of Symbolic Logic with Kalish-Montague derivations Copyright 2006-13 by Terence Parsons all rights reserved Aug 2013 Preface The system of logic used here is essentially that of Kalish &

### GENERAL NOTES ON THIS CLASS

PRACTICAL LOGIC Bryan Rennie GENERAL NOTES ON THE CLASS EXPLANATION OF GRADES AND POINTS, ETC. SAMPLE QUIZZES SCHEDULE OF CLASSES THE SIX RULES OF SYLLOGISMS (and corresponding fallacies) SYMBOLS USED

### Criticizing Arguments

Kareem Khalifa Criticizing Arguments 1 Criticizing Arguments Kareem Khalifa Department of Philosophy Middlebury College Written August, 2012 Table of Contents Introduction... 1 Step 1: Initial Evaluation

### Intersubstitutivity Principles and the Generalization Function of Truth. Anil Gupta University of Pittsburgh. Shawn Standefer University of Melbourne

Intersubstitutivity Principles and the Generalization Function of Truth Anil Gupta University of Pittsburgh Shawn Standefer University of Melbourne Abstract We offer a defense of one aspect of Paul Horwich

### ON THE TRUTH CONDITIONS OF INDICATIVE AND COUNTERFACTUAL CONDITIONALS Wylie Breckenridge

ON THE TRUTH CONDITIONS OF INDICATIVE AND COUNTERFACTUAL CONDITIONALS Wylie Breckenridge In this essay I will survey some theories about the truth conditions of indicative and counterfactual conditionals.

### Phil 3304 Introduction to Logic Dr. David Naugle. Identifying Arguments i

Phil 3304 Introduction to Logic Dr. David Naugle Identifying Arguments Dallas Baptist University Introduction Identifying Arguments i Any kid who has played with tinker toys and Lincoln logs knows that

### HANDBOOK (New or substantially modified material appears in boxes.)

1 HANDBOOK (New or substantially modified material appears in boxes.) I. ARGUMENT RECOGNITION Important Concepts An argument is a unit of reasoning that attempts to prove that a certain idea is true by

### LGCS 199DR: Independent Study in Pragmatics

LGCS 99DR: Independent Study in Pragmatics Jesse Harris & Meredith Landman September 0, 203 Last class, we discussed the difference between semantics and pragmatics: Semantics The study of the literal

### Unit. Categorical Syllogism. What is a syllogism? Types of Syllogism

Unit 8 Categorical yllogism What is a syllogism? Inference or reasoning is the process of passing from one or more propositions to another with some justification. This inference when expressed in language

### BASIC CONCEPTS OF LOGIC

1 BASIC CONCEPTS OF LOGIC 1. What is Logic?... 2 2. Inferences and Arguments... 2 3. Deductive Logic versus Inductive Logic... 5 4. Statements versus Propositions... 6 5. Form versus Content... 7 6. Preliminary

### What would count as Ibn Sīnā (11th century Persia) having first order logic?

1 2 What would count as Ibn Sīnā (11th century Persia) having first order logic? Wilfrid Hodges Herons Brook, Sticklepath, Okehampton March 2012 http://wilfridhodges.co.uk Ibn Sina, 980 1037 3 4 Ibn Sīnā

### Ayer and Quine on the a priori

Ayer and Quine on the a priori November 23, 2004 1 The problem of a priori knowledge Ayer s book is a defense of a thoroughgoing empiricism, not only about what is required for a belief to be justified

### Chapter 3: More Deductive Reasoning (Symbolic Logic)

Chapter 3: More Deductive Reasoning (Symbolic Logic) There's no easy way to say this, the material you're about to learn in this chapter can be pretty hard for some students. Other students, on the other

### 6. Truth and Possible Worlds

6. Truth and Possible Worlds We have defined logical entailment, consistency, and the connectives,,, all in terms of belief. In view of the close connection between belief and truth, described in the first

### Complications for Categorical Syllogisms. PHIL 121: Methods of Reasoning February 27, 2013 Instructor:Karin Howe Binghamton University

Complications for Categorical Syllogisms PHIL 121: Methods of Reasoning February 27, 2013 Instructor:Karin Howe Binghamton University Overall Plan First, I will present some problematic propositions and

### Durham Research Online

Durham Research Online Deposited in DRO: 20 October 2016 Version of attached le: Published Version Peer-review status of attached le: Not peer-reviewed Citation for published item: Uckelman, Sara L. (2016)

### THE PROBLEM OF CONTRARY-TO-FACT CONDITIONALS. By JOHN WATLING

THE PROBLEM OF CONTRARY-TO-FACT CONDITIONALS By JOHN WATLING There is an argument which appears to show that it is impossible to verify a contrary-to-fact conditional; so giving rise to an important and

### Can Negation be Defined in Terms of Incompatibility?

Can Negation be Defined in Terms of Incompatibility? Nils Kurbis 1 Abstract Every theory needs primitives. A primitive is a term that is not defined any further, but is used to define others. Thus primitives

### Semantic Foundations for Deductive Methods

Semantic Foundations for Deductive Methods delineating the scope of deductive reason Roger Bishop Jones Abstract. The scope of deductive reason is considered. First a connection is discussed between the

### Chapter 3 Disputes and Definitions

Logic: A Brief Introduction Ronald L. Hall, Stetson University Chapter 3 Disputes and Definitions 3.1 Disputes I: Attitudes and Beliefs At this point we must deal with one more consequence that the recognition

### PHIL 115: Philosophical Anthropology. I. Propositional Forms (in Stoic Logic) Lecture #4: Stoic Logic

HIL 115: hilosophical Anthropology Lecture #4: Stoic Logic Arguments from the Euthyphro: Meletus Argument (according to Socrates) [3a-b] Argument: Socrates is a maker of gods; so, Socrates corrupts the

### Truth and Modality - can they be reconciled?

Truth and Modality - can they be reconciled? by Eileen Walker 1) The central question What makes modal statements statements about what might be or what might have been the case true or false? Normally

### Necessity and Truth Makers

JAN WOLEŃSKI Instytut Filozofii Uniwersytetu Jagiellońskiego ul. Gołębia 24 31-007 Kraków Poland Email: jan.wolenski@uj.edu.pl Web: http://www.filozofia.uj.edu.pl/jan-wolenski Keywords: Barry Smith, logic,

### Logic Book Part 1! by Skylar Ruloff!

Logic Book Part 1 by Skylar Ruloff Contents Introduction 3 I Validity and Soundness 4 II Argument Forms 10 III Counterexamples and Categorical Statements 15 IV Strength and Cogency 21 2 Introduction This

### 1.2. What is said: propositions

1.2. What is said: propositions 1.2.0. Overview In 1.1.5, we saw the close relation between two properties of a deductive inference: (i) it is a transition from premises to conclusion that is free of any

### CHAPTER 1 A PROPOSITIONAL THEORY OF ASSERTIVE ILLOCUTIONARY ARGUMENTS OCTOBER 2017

CHAPTER 1 A PROPOSITIONAL THEORY OF ASSERTIVE ILLOCUTIONARY ARGUMENTS OCTOBER 2017 Man possesses the capacity of constructing languages, in which every sense can be expressed, without having an idea how

### Contemporary Theology I: Hegel to Death of God Theologies

Contemporary Theology I: Hegel to Death of God Theologies ST503 LESSON 19 of 24 John S. Feinberg, Ph.D. Experience: Professor of Biblical and Systematic Theology, Trinity Evangelical Divinity School. In

### SYLLOGISTIC LOGIC CATEGORICAL PROPOSITIONS

Prof. C. Byrne Dept. of Philosophy SYLLOGISTIC LOGIC Syllogistic logic is the original form in which formal logic was developed; hence it is sometimes also referred to as Aristotelian logic after Aristotle,

### CHAPTER ONE STATEMENTS, CONNECTIVES AND EQUIVALENCES

CHAPTER ONE STATEMENTS, CONNECTIVES AND EQUIVALENCES A unifying concept in mathematics is the validity of an argument To determine if an argument is valid we must examine its component parts, that is,

### Chapter 6. Fate. (F) Fatalism is the belief that whatever happens is unavoidable. (55)

Chapter 6. Fate (F) Fatalism is the belief that whatever happens is unavoidable. (55) The first, and most important thing, to note about Taylor s characterization of fatalism is that it is in modal terms,

### IS THE SYLLOGISTIC A LOGIC? it is not a theory or formal ontology, a system concerned with general features of the

IS THE SYLLOGISTIC A LOGIC? Much of the last fifty years of scholarship on Aristotle s syllogistic suggests a conceptual framework under which the syllogistic is a logic, a system of inferential reasoning,

### Unit 4. Reason as a way of knowing. Tuesday, March 4, 14

Unit 4 Reason as a way of knowing I. Reasoning At its core, reasoning is using what is known as building blocks to create new knowledge I use the words logic and reasoning interchangeably. Technically,

### Negative Facts. Negative Facts Kyle Spoor

54 Kyle Spoor Logical Atomism was a view held by many philosophers; Bertrand Russell among them. This theory held that language consists of logical parts which are simplifiable until they can no longer

### Philosophy 240: Symbolic Logic

Philosophy 240: Symbolic Logic Russell Marcus Hamilton College Fall 2011 Class 27: October 28 Truth and Liars Marcus, Symbolic Logic, Fall 2011 Slide 1 Philosophers and Truth P Sex! P Lots of technical

### Is the law of excluded middle a law of logic?

Is the law of excluded middle a law of logic? Introduction I will conclude that the intuitionist s attempt to rule out the law of excluded middle as a law of logic fails. They do so by appealing to harmony

### 3.3. Negations as premises Overview

3.3. Negations as premises 3.3.0. Overview A second group of rules for negation interchanges the roles of an affirmative sentence and its negation. 3.3.1. Indirect proof The basic principles for negation

### Can Negation be Defined in Terms of Incompatibility?

Can Negation be Defined in Terms of Incompatibility? Nils Kurbis 1 Introduction Every theory needs primitives. A primitive is a term that is not defined any further, but is used to define others. Thus

### 4.1 A problem with semantic demonstrations of validity

4. Proofs 4.1 A problem with semantic demonstrations of validity Given that we can test an argument for validity, it might seem that we have a fully developed system to study arguments. However, there

### Russell on Plurality

Russell on Plurality Takashi Iida April 21, 2007 1 Russell s theory of quantification before On Denoting Russell s famous paper of 1905 On Denoting is a document which shows that he finally arrived at

### Instrumental reasoning* John Broome

Instrumental reasoning* John Broome For: Rationality, Rules and Structure, edited by Julian Nida-Rümelin and Wolfgang Spohn, Kluwer. * This paper was written while I was a visiting fellow at the Swedish

### 6.5 Exposition of the Fifteen Valid Forms of the Categorical Syllogism

M06_COPI1396_13_SE_C06.QXD 10/16/07 9:17 PM Page 255 6.5 Exposition of the Fifteen Valid Forms of the Categorical Syllogism 255 7. All supporters of popular government are democrats, so all supporters

### Lecture 4. Before beginning the present lecture, I should give the solution to the homework problem

1 Lecture 4 Before beginning the present lecture, I should give the solution to the homework problem posed in the last lecture: how, within the framework of coordinated content, might we define the notion

### 5.3 The Four Kinds of Categorical Propositions

M05_COI1396_13_E_C05.QXD 11/13/07 8:39 AM age 182 182 CHATER 5 Categorical ropositions Categorical propositions are the fundamental elements, the building blocks of argument, in the classical account of

### SECTION 2 BASIC CONCEPTS

SECTION 2 BASIC CONCEPTS 2.1 Getting Started...9 2.2 Object Language and Metalanguage...10 2.3 Propositions...12 2.4 Arguments...20 2.5 Arguments and Corresponding Conditionals...29 2.6 Valid and Invalid,

### Transition to Quantified Predicate Logic

Transition to Quantified Predicate Logic Predicates You may remember (but of course you do!) during the first class period, I introduced the notion of validity with an argument much like (with the same

### HANDBOOK (New or substantially modified material appears in boxes.)

1 HANDBOOK (New or substantially modified material appears in boxes.) I. ARGUMENT RECOGNITION Important Concepts An argument is a unit of reasoning that attempts to prove that a certain idea is true by