001 logic08_reasoning
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This document discusses reasoning, inference, truth, validity, and the structure of arguments. It defines reasoning as passing from known information to unknown information through inference. Inference is drawing a conclusion based on given premises. An argument consists of premises that provide support for a conclusion. There are two types of inference: deductive, where the premises guarantee the truth of the conclusion, and inductive, where the premises make the conclusion likely or probable but not certain. For an argument to be valid, the conclusion must follow logically from the premises, but the premises and conclusion may not be factually true. For an argument to be sound, the argument must be valid and the premises and conclusion must be factually true.
001 logic08_reasoning
- 2. REASONING (…meaning) • 5.1. Reasoning -- a mental process whereby we pass from what we know (known) to what we do not know (unknown) (Timbreza). That which is inferred from unknown to known is called the conclusion; also called an inferential thinking
- 3. Inference… • 5.2. Inference -- a mental process by which we pass from one or more propositions to some other propositions consequently related to the former; draws a conclusion from given premises
- 4. Argument… • 5.3. The Structure of Argument: primary concern of logic is how the truth of some propositions is connected with the truth of another; Argument -- a set of two or more propositions related to each other in such a way that all but one of them (the premises) is supposed to provide support for the remaining one (the conclusion).
- 5. Cont’n… • 5.3.1. Unrelated propositions -- the truth or falsity of each has no bearing on that of the others. Ex.: Few shoppers are foreigners who love to buy souvenir items
- 6. Cont’n… • 5.3.2. Example of an argument: Fr. Kurt Piskaty is a priest. Therefore, Fr. Kurt Piskaty is celibate since all priests are celibates. The conclusion, Fr. Kurt Piskaty is celibate, is inferentially drawn from its premises, ‘ Fr. Kurt Piskaty is a priest and All priests are celibates.
- 7. Kinds of Inference • 5.4. Two kinds of Inference: deductive and inductive inferences • 5.4.1. Deductive Inference -- claims that the truth of its premises guarantees the truth of its conclusion; holds to a very high standard of correctness; succeeds only if its premises provide such absolute and complete support for its conclusion that it would be utterly inconsistent to suppose that the premises are true but the conclusion false (Ex.: All players are athletic. Michael is a player. Therefore, Michael is athletic)
- 8. Cont’n… • 5.4.2. Inductive Inference – an argument which merely claims that the truth of its premises makes it likely or probable that its conclusion is also true (Ex.: Some leaders in the government are corrupt. My neighbors are leaders in the government. Therefore, my neighbors are corrupt.
- 9. Truth and Validity • 5.5. Truth and Validity: Truth refers to the conformity of the proposition to the reality. • Logic refers to the connection between the premises and the conclusion of an argument. • A logical argument has propositions that are not necessarily true in reality although the conclusion follows from the truth of the premises.
- 10. Cont’n… • An example of a logical argument is: • All speakers are fluent in English. Fidel Castro is a speaker. Therefore, Fidel Castro is fluent in English.
- 11. Cont’n… Soundness is a property of an argument as a whole. This means that the argument does not only have logical connection in both premises and conclusion but that the propositions are true in reality. An example of a sound argument is this: Every person is created by God. Susie is a person. Therefore, Susie is created by God. 2nd TO THE LAST SLIDE
- 12. Cont’n… • Illogical arguments may have premises that are true in reality but there is no connection between premises and the conclusion. An example of an illogical argument is this: All tigers are animals. All lions are animals. Therefore, all lions are tigers. END OF THE TOPIC