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Hypothetical Syllogism
This document discusses different types of logical syllogisms: 1. Hypothetical syllogism uses a conditional premise and categorical conclusions. There are three types of hypothetical propositions: conditional, disjunctive, and conjunctive. 2. Conditional syllogism uses a conditional premise and its valid forms are modus ponens and modus tollens. 3. Disjunctive syllogism uses a disjunctive premise and its valid forms are ponendo tollens and tollendo ponens. 4. Conjunctive syllogism uses a conjunctive premise stating two choices cannot be true together. It provides examples and
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Hypothetical Syllogism
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- 2. HYPOTHETICAL SYLLOGISM Ahypothetical syllogism is one wherein the major premise is a hypothetical proposition, and the minor premise and conclusion are categorical proposition. There are three types of hypothetical propositions: 1. Conditional 2. Disjunctive 3. Conjunctive
- 3. CONDITIONAL SYLLOGISM Itis one whose major premise is a conditional proposition and whose minor premise and conclusion are categorical propositions. It consists of the antecedent and the consequent for the truth of the hypothetical judgment lies in the truth of dependence between the two clauses. Antecedent – (CAUSE) Consequent – (EFFECT)
- 4. EXAMPLE: MAJOR PREMISE– If illegal loggers continue cutting trees, then the forest will be devastated. MINOR PREMISE – Illegal loggers continue cutting trees. CONCLUSION – Therefore, the forest will be devastated.
- 5. VALID MOODS OFA CONDITIONAL SYLLOGISM 1. MODUS PONENS 2. MODUS TOLLENS
- 6. MODUS PONENS Thetruth of the antecedent implies the truth of the consequence. It is also known as positing mood (assert) or the empirical conditional constructive syllogism. The fulfilment of the condition implies the occurrence of the consequent.
- 7. EXAMPLE: Valid mood(accepting the antecedent) If A is B, then X is Y. But A is B. Therefore, X is Y. 1) If Myra talks, then she speaks. But Myra is talking. Therefore, Myra is speaking.
- 8. EXAMPLE: Invalid mood(rejecting the antecedent) If a person has cancer, then he is seriously ill. But Mang Nestor is not sick of cancer. Therefore, Mang Nestor is not seriously ill.
- 9. MODUS TOLLENS Thefalsity of the consequent implies the falsity of the antecedent. I t is also known as sublating mood or empirical conditional destructive syllogism. If the consequent is rejected in the minor premise, the antecedent must also be rejected in the conclusion.
- 10. EXAMPLE: Valid mood(rejecting the consequent) If A is B, then X is Y. But X is not Y. Therefore, A is not B. 1) If Martin is a policeman, then people will respect and follow him. But people will not respect and follow him. Therefore, Martin is not a policeman.
- 11. DISJUNCTIVE SYLLOGISM Themajor premise is a disjunctive proposition and the minor premise and conclusion are categorical propositions. It is an “either or” statement.
- 12. EXAMPLE: A iseither B or C. But A is B. Therefore, A is not C. 1) The weather forecast is either accurate or imprecise. But the weather forecast is imprecise. Therefore, it is not accurate.
- 13. MOODS OF THEDISJUNCTIVE SYLLOGISM Complete Disjunctive – parts contradict each other.
- 14. VALID MOODS ARE POSSIBLE: 1.PONENDO TOLLENS 2. TOLLENDO PONENS
- 15. VALID MOODS AREPOSSIBLE Ponendo Tollens – positing mood (accept or affirm), minor premise affirms one of the alternatives of the major premise and the conclusion denies the other.
- 16. EXAMPLE: The suspectis either guilty or innocent. But the suspect is innocent. Therefore, the suspect is not guilty.
- 17. Tollendo Ponens– sublating mood (sublate or negative), minor premise deny the alternative of the major premise and the conclusion affirms the other.
- 18. EXAMPLE: Fast-food iseither healthy or unhealthy. But fast-food is unhealthy. Therefore, it is not healthy.
- 19. CONJUNCTIVE SYLLOGISM Themajor premise is a conjunctive proposition (one that denies that the two choices can be true at the same time) and that the minor premise and the conclusion and the conclusions are categorical propositions.
- 20. EXAMPLE: Our branchesof government cannot be either executive or parliamentary. But it is executive. Therefore, it is not parliamentary.
- 22. Group 3 Selfiew/ Sir Urs
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