BASIC CONCEPTS

1. BASIC CONCEPTS References: Hurley, Patrick J. A Concise Introduction to Logic. Paperback. Tenth Edition. California: Thomson Wadsworth, 2008. “The Types of Arguments”. Available http://www.internetlogic.org/argtypes.html

2. ARGUMENTS • Argument: a group of statements, one of which (the conclusion) is claimed to follow from the other or others (the premises). • Good arguments: those in which the conclusion really does follow from the premises • Bad arguments: those in which does not, even though it is claimed to

3. Statement • Basis: Argument as a group of statement • Statement: a sentence that is either true or false; typically a declarative sentence. • Examples: • Hydrogen is combustible. • World War II began in 1939. • Some ducks are fish. • Abraham Lincoln was beheaded.

4. Truth - Value • Truth value of the statement: the attribute by which a statement is either true or false. • Examples: • Hydrogen is combustible. (true) • World War II began in 1939. (true) • Some ducks are fish. (false) • Abraham Lincoln was beheaded. (false)

5. Non-Statements • Sentences which cannot be said to be either true or false. • What is the atomic weight of carbon? (question) • Let’s go to the park today. (proposal) • We suggest that you travel by bus. (suggestion) • Turn to the left at the next corner. (command) • Ouch! (exclamation)

6. Components of an Argument: Premise(s) and conclusion • Premises: the statement that set forth the evidence. • Conclusion: the statement that is claimed to follow from the evidence. • Example: • All cats are animals. • Felix is a cat. • Therefore, Felix is an animal. • N.B. the first two statements are the premises; the third is the conclusion. • The claim that the conclusion follows from the premises is indicated by the word “therefore”.

7. Schema of an Argument:

8. Recognizing Arguments • One of the most important tasks in the analysis of arguments is being able to distinguish premises from conclusion. • If what is thought to be a conclusion is really a premise, and vice versa, the subsequent analysis cannot possibly be correct. • Frequently, arguments contain certain indicator words that provide clues in identifying premises and conclusion.

9. Conclusion Indicator • A word that provides a clue to identifying a conclusion. • Examples • Therefore hence whence • Wherefore thus consequently • Accordingly so it follows that • Entails that as a result We may conclude • Implies that it must be that We may infer • Whenever a statement follows one of these indicators, it can usually be identified as the conclusion. • By process of elimination the other statements in the argument are the premises. • Example: This is pen is out of ink. Consequently, it will not write.

10. Premise Indicator • A word that provides a clue to identifying a premise. • If an argument does not contain a conclusion indicator, it may contain a premise indicator. • Examples: • for the reason that in that seeing that • As indicate by for since • Because as inasmuch as • may be inferred from given that owing to • Any statement following one of these indicators can usually be identified as a premise. • Example: This locket is worth a lot of money, since it is made of platinum.

11. Inference & Proposition • An inference, in the technical sense of the term, is the reasoning process used to produce an argument. • A proposition, in the technical sense, is the meaning or information content of a statement.

12. Passages lacking an inferential claim (1) • Passages lacking an inferential claim contain statements that could be premises or conclusions (or both) but what is missing is a claim that a reasoning process is being expressed. • Warnings/ pieces of advice: kinds of discourse aimed at modifying someone’s behavior. • Ex. “Watch out that you don’t slip on the floor.” • Ex. “I suggest you take philosophy in the first semester.” • Each of these could serve as the conclusion of an argument; but in their present context, there is no claim that they supported or implied by reasons of evidence. • Statements of beliefs or opinion: expressions of what someone happen to believe or think at a certain time. • Ex. I think a nation such as ours, with its high moral traditions and commitments, has a further responsibility to know how to became drawn into this conflict, and to learn the lessons it has to teach us for the future. • Alfred Hassler, Saigon, U.S,A.

13. Passages lacking an inferential claim (2) • Loosely associated statements: may be about the same general subject, but they lack a claim that one of them is proved by the others. • Ex. Not to honor men of worth will keep the people from contention; not to value goods that are hard to come by will keep them from theft; not to display what is desirable will keep them from being unsettled of mind. • Lao-Tzu, Thoughts from the Tao Te Ching • Report: consists of a group of statements that convey information about some situation or event. Ex. News Report • Expository passage: a kind of discourse that begins with a topic sentence followed by one or more sentences that develop the topic sentence. • Illustration: consists of a statement about certain subject combined with a reference to one or more specific instances intended to exemplify that statement. • Ex. Chemical elements, as well as compounds, can be represented by molecular formulas. Thus, oxygen is represented by “O2”, sodium chloride by “NaCl”, and sulfuric acid by “H2SO4”.

14. Conditional Statements • A conditional statement is an “if… then…” statement. • Ex. If it rains, the soil is wet. • It is made up of two component statements: if = antecedent; then = consequent • Occasionally, “then” is left out • Conditional statements are not arguments because there is no claim that either the antecedent or the consequent presents evidence. • In other words, there is no assertion that either the antecedent or the consequent is true. Rather, there is only the assertion that if the antecedent is true, then so is the consequent. • A conditional statement may serve as premise or the conclusion of an argument.

15. Explanations • An explanation consists of a statement or a group of statements intended to shed light on some phenomenon that is usually accepted as a matter of fact. • Ex. Cows can digest grass, while humans cannot, because their digestive systems contain enzymes not found in humans. • 2 parts: • Explanandum: the statement that describes the event or phenomenon to be explained. • Explanans: the statement or group of statements that purports to do the explaining. • Explanations are sometimes mistaken for arguments because they often contain the indicator word “because”. Yet explanations are not arguments for the following reason: In an explanation, the explanans is intended to show why something is the case, whereas in an argument the premises are intended to prove that something is the case.

16. SCHEMATIC DIAGRAM Premises Explanans Conclusion Explanandum

17. Types of Arguments: Deduction and Induction • Deductive arguments are those meant to work because of their pattern alone, so that if the premises are true the conclusion could not be false. • Inductive (or just non-deductive) arguments are meant to work because of the actual information in the premises so that if the premises are true the conclusion is not likely to be false. • Difference: between certainty (we can be sure the conclusion is correct) and probability (we can bet on the conclusion being correct)

18. Validity, Soundness, Strength, Cogency • Valid: A deductive argument with the right form regardless of the truth of the premises. • Sound: When the premises are in fact true and the argument is valid. • Strong / Weak: Inductive arguments can be seen as strong (the conclusion is more likely to be true because of support provided by the premises) or as weak. • Cogent: When an inductively strong argument does have true premises.