Notes on Introduction to Logic -- Phil A101

William Jamison - Instructor

Lecture 2:

As soon as you get the text and have some time, please read through the Preface and start Chapter 1. More thoughts on lecture 1?

Chapter 1 Logic and Language

The role of the consonants in the mnemonic names of syllogisms:

http://www.scribd.com/doc/13043055/Syllogism

Basic Logical Concepts

First we go into Informal Analysis of Statements by talking about the nature of sentences and what we mean by propositions or statements.

Sentences  

            We distinguish the physical aspects of our language from the meaning it has for us. To talk about the meaning we use the words “statement” or “proposition” instead of “sentence.”

 Exercises are to help clarify the above difference. Do you see why this is an important difference?

Not from the text but good to know: Some logicians make a distinction between cognitive and non-cognitive uses of sentences. Is the sentence used to make a statement that is true or false? Can the sentence be used in any other way? It seems that what we call declarative sentences can be used to make statements that are true or false. Imperatives, exclamations, and questions are not true or false. Why is this the case? A sentence may be of non-declarative form but still used to make a statement that is declarative and have truth value (that is be true or false). What kind of intonation does the speaker have to use to utter a sentence that is non-declarative in form to use it to make a declarative statement?

Statements

            What about recordings of statements? Is the difference in verbalizing the sentence or something else? Think about the difference between brain states and thoughts. I wonder if there is something common here about the way we want to think about our subjective experience of objective phenomena. To keep it simple, statements or propositions will be true or false. (But see Pierce to make it complicated).

 Recognizing Sentences Used to Express Statements

            You might think about who determines what a statement means at this point. It seems to me that the audience determines what you meant regardless of what you intended to mean! The speaker must receive feedback and decide if the feedback is what was expected. If not, a different way must be tried to transmit that message until the audience reacts the way the speaker expects. Is this how we communicate?

A couple of points I may or may not discuss at this point, but eventually will: Here would be a good place to discuss the “Boo-Hooray” theory of meaning.

Self-Evident and Supported Statements

            Syntactically analytic statements seem to be free of the critique Quine gives analyticity in his work. Semantically analytic statements do not.

“Call an observation categorical analytic for a given speaker if, as in 'Robins are birds', the affirmative stimulus meaning for him of the one component is included in that of the other. Otherwise synthetic. Call a sentence or set of sentences testable if it implies some synthetic observation categoricals. Call two observation categoricals synonymous if their respective components have the same stimulus meanings. Then the empirical content of a testable sentence or set of sentences for that speaker is the set of all the synthetic observation categoricals that it implies, plus all synonymous ones. I add the synonymous ones so that merely verbal variation will not obstruct sameness of content.” (Quine, Pursuit of Truth pp. 16-17). We will see the source of these relationships when we look at the square of opposition.

            Have you ever heard a politician say something semantically analytic? Wouldn’t that be psychologically persuasive to those that did not mull it over? They can say a lot this way, without saying anything we would disagree with! The trick is saying contingent or synthetic statements and still finding an agreeable audience. But if the main reason we speak to one another is to voice disagreement, how much better off a speaker is that sticks to analytic statements!

Logical Relationships between Two (or More) Propositions

            This is why the set of beliefs a person has can be coherent or incoherent. Each belief can be voiced as a statement. Do all the statements we accept go together or are there conflicts? If there are conflicts, do we experience cognitive dissonance?

Consistency

            Aristotle argues that the person who denies they have to be consistent in their arguments cannot argue his point. Yet it does seem like we can believe contrary things without breaking down. Imagine a computer trying to operate with contradictory instructions! A dialectical interpretation of the nature of things suggests that each “thing” implies its opposite! An interesting book here is John Barrow’s Impossibility. Another issue: Does the religious mind require an ability to think incoherent views together?       

Real versus Apparent Disagreements

            In light of this, are most disagreements real or only apparent? Imagine people speaking with one another but using words in different ways in different contexts. If they do not mean the same things, how can they have a real disagreement?

Verbal Disagreements

            What would you consider "poor"? If we disagreed on what we meant by the word chances are that our arguments about the subject would be an apparent disagreement, but not a real disagreement. Someone could help us resolve the dispute by getting us to define what we each meant by "poor".

            Does it help us if we determine that a disagreement is merely verbal?

Arguments consist of premises and a conclusion. There are premise indicators and conclusion indicators in our language. The book gives a list of each. Go through the exercises to see if you can pick out premises and conclusions. Remember that not all premises or even the conclusion may be actually spoken but may be left for the audience to "fill in". This is a powerful technique since it psychologically encourages  agreement.

It should be noted that there is a difference between arguments and explanations. A list of events is not an argument but can be used to support one.

Implication: We will do much more with this through out the course.

Logical Equivalence

            Implication both ways? We are not talking necessarily about the same sets of things, but the truth value of the statements!

Independence

            Are we talking about completely different sets of things?

Please e-mail me if you find anything amiss or have ideas to make these pages more useful.

 Lecture 3.