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Basic Terms in Logic

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  1. Basic Terms in Logic Michael Jhon M. Tamayao

  2. Learning Objectives • Identify and define the basic terms in Logic. • Differentiate the terms according to their use. • Apply the terms in practical cases.

  3. Introduction • Terms – basic elements that make up a language system. • The language of logic girds towards order.

  4. What is LOGIC? • “logos” = word, reason or principle • Logic – science of correct reasoning. ! Systematized ! Evokes ORDER • What does Logic put into order?

  5. 1.) All men are mammals All students are men :: All students are mammals. 2.) All monkeys eat banana George Lincoln eats banana :: George Lincoln is a monkey

  6. What logic puts in order is the way we reason out. • Logic makes explicit the rules of reasoning.

  7. Inference – the process of deducing or extracting a statement (conclusion) from the previous statement/s. • Argument – the verbal expression of inference. • Syllogism – the format of arguments with three statements. • Conclusion – the statement being supported. • Premises – the statement/s that support/s the conclusion.

  8. Key Terms • ARGUMENT PREMISES INFERENCE CONCLUSION SYLLOGISM

  9. What is the importance of studying the Arguments? • The answer: It is the way we support our claims to truth and validity. • Truth and validity are the two aspects that measure the worth of an argument.

  10. What is TRUTH in Logic? • Truth – the correspondence or equivalence of the mind to reality/object. Object Statement “The Horse is white”

  11. The truth value of a statement is not proven by logicians but of empirical scientists, researchers and private detectives. • Logicians only study the reasoning found on statements and not the question of their truth values.

  12. Judgment – the “act” by which the mind affirms or denies an attribute of a subject. – The simplest act of the mind in which it can attain truth. Proposition – “statement” that affirms or denies something. – verbal expression of judgment

  13. Simple Apprehension - more elementary “act” of the mind than judgment – conceiving a notion of something. “The Horse is white.” – verbally expressed as a term/name. • Terms – the two notions in a proposition: subject and predicate

  14. Acts of the Mind Simple Apprehension Judgment Inference Verbal Expression Term/Name Proposition Argument/Syllogism

  15. Propositions: Quality and Quantity 1. Quality – affirmative negative • Affirmative - predicate is affirmed of the subject. ex. The audience is kind. • Negative - predicate is denied of the subject. ex. The audience is not kind.

  16. 2. Quantity – universal or particular Universal – the predicate is affirmed or denied of “the whole” subject. Ex. “All” men are beings with heart. “Not all” men are beings with heart. Particular – the predicate is affirmed or denied of only “part of” the subject. Ex. “Some” men are haughty. Some men not are haughty.

  17. Four-fold Scheme of Proposition • A-type: universal and affirmative “All men are mortal” • I-type: Particular and Affirmative “Some men are philosophers” • E-type: Universal and Negative “Not all philosophers are rich.” • O-type: Particular and Negative “Some men are not rich.”

  18. Terms also have “quantity” but not “quality” • Singular terms ex. Socrates, Plato, Aristotle • Universal Terms ex. Men, horse

  19. What is meant by VALIDITY? • An argument is valid if the premises do provide conclusive grounds for the conclusion. Otherwise, the argument is invalid. • Validity follows the different rules of inference.

  20. Validity pertains to arguments/reasoning. • Truth pertains to propositions. • Logic has for its first principle the independence of truth and validity.

  21. Independence of truth from validity • Example: All men are animals All creatures are men ::All creatures are animals. Although two statements are false, the argument is still valid. FALSE

  22. Key Terms TRUTH and VALIDITY simple apprehension Judgment inference

  23. “Sound” Argument – the reasoning in the argument is valid and all the statements are true. • Example: All computers are technological products All abacuses are computers :: All abacuses are technological products.

  24. 2 Kinds of Arguments 1.) Deductive argument - An argument that has premises which gives conclusive grounds for the truth of the conclusion, or if the premises claim to support the conclusion with necessity. - The process is exact. e.g. All priests are humans. All Popes are priests. :: All Popes are humans.

  25. 2.) Inductive Argument - Makes the wilder claim that its premises support but do not guarantee the necessity of its conclusion. - The conclusion is only given a high probability of correctness and “not” exactly valid or invalid. Ex. Of all the 50 million swans I saw, nothing is black. :: No swan is black.

  26. DEDUCTIVE INDUCTIVE • Exact • Valid or invalid • Not a matter of degree (All or Nothing) • Probable • Strong or weak • A matter of degree (More or Less) Key Terms

  27. What is a FALLACY? • Fallacy – bad method of argument, whether deductive or inductive. – one or more of its premises are false, or the reasoning from them may be invalid, or the language expressing them may be ambiguous or vague. – typical faults in arguments that sounds persuasive.

  28. Ex. All Stars are hot. I am a Star. :: I am hot. There is ambiguity in the meaning of the word star.

  29. Recap • Logic – the science of correct reasoning. • Inference – the process of deducing or extracting a statement (conclusion) from the previous statement/s. • Argument – is a kind of reasoning/inference in which statements are offered to support or justify another statement. • Syllogism – the format of arguments with three statements.

  30. Conclusion – the statement being supported. • Premises – the statement/s that support/s the conclusion. • Truth – the correspondence or equivalence of the mind to reality/object. • Judgment – the “act” by which the mind affirms or denies an attribute of a subject. • Propositions – verbal expression of judgments.

  31. Simple Apprehension – conceiving of the notion of something. • Term – verbal expression of notions. • Quality – may either be affirmative or negative. • Quantity – may either be universal or particular.

  32. Valid argument – an argument which has premises that provide conclusive grounds for its conclusion. • Sound Argument – an argument with valid reasoning and all its statements are true. • Deductive argument – an argument with premises that claim to support the conclusion with necessity.

  33. Inductive Argument – argument with premises that support but do not guarantee the necessity of its conclusion. • Fallacy – a bad argument that has one or more false statements and/or invalid reasoning that sounds persuasive.

  34. END Thank you for listening!