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PHL245_h1s_UP_TO_FEB16 - Day 1 2011 1 10 9:38 Modern...

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Day 1 2011 1 10 년 년년년 년년 9:38 Modern symbolic logic is a study of deductive reasoning o Valid deductive argument that has true premises yields true conclusions o Logic is to understand critical analysis of what is true and what is false By using symbols, confusing sentences are disambiguated. o Makes my thinking clear o Words are messy o But logic will miss nuisances It is modern after Aristotle o Syllogistic logic is created, basically, by Aristotle o Leibniz is the father of symbolic logic o Frege is founder of mathematical logic o Bertrand Russell creates the basis for this course o Logicomix - book of comical inference to Russell What is a logical argument? o Justification for the conclusion o If it is a good argument, justification will be true and conclusion will follow. o Premises are the justifications Premises and conclusions must have truth value, aka propositions o Has truth value now, or will have soon or later Inference indicators o Necessary for identifying arguments in messy philosophical texts o Premise indicator Because, as indicated by, being that, etc… o Conclusion indicators Therefore, accordingly, so, etc… When inference indicators introduce explanation and description, they are not inference indicators Pick out the premises from other bits of writing (elaboration, illustration, explanation, filler) Example of a logical argument 1) Some students will pass this course Nobody passes who doesn't do at least some of the exercises ------------------------------------------------------------ Some students in this class will do the exercises
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Logic is based on bivalent propositions o Propositions are all truth or false o This matters since we will not care about language if there is no degree of truth or falsity in language Sentences o Propositions can be true or false based on nowadays' facts o Propositions could be true or false without us knowing the facts o An order, or imperative sentences are not propositions, - often they are conclusions She bases her lecture on the readings given. Day 2 2011 1 12 년 년년년 년년 9:38 Validity is that o If the premises are true, then is the conclusion true as well? o When the two correspond, where premises are true and conclusion follows the premise, then it is valid. Soundness is o the truthfulness of the conclusions o This can be checked by empirical or theoretical works Validity suggests that when truthfulness concurs in both premises and the conclusion, the argument must be strong, except in the case of: o The argument is circular The conclusion is presupposed, or included, in the premise Ex. God exists because bible exists and bible is the word of God. But the conclusion (God exists) is supposed in the premise that (bible is the word of God) You have to find premises that people will accept, then argue for your conclusion Hence, circular, begging the question is valid but not strong argument, which does not go anywhere except in circles and ceases to be an argument o Tautology
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