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LIBERTY PHIL 201 - PHIL201_Study_Guide_Lesson_4

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PHIL 201STUDY GUIDE: LESSON 4A Little LogicLesson OverviewLogic is the primary tool or methodology in studying philosophy. Philosophy is about analyzing and constructing arguments and a good understanding of the basics of logical reasoning is essential in performing that task. The next 3 lessons will focus on logic and analyzing arguments.In this lesson, you will first be introduced to the laws of logic. These are the first principles for all reasoning. We will then discuss the specialized terminology we use in logic. Finally, we will examine 2 major kinds of logical reasoning: deductive and inductive. We will consider different forms of arguments under each and discuss how to evaluate these arguments. Take note that a large part of this lesson is about learning the terminology for logic.TasksRead and take notes from Prelude to Philosophy, Chapter 5: “A Little Logic.” As you read, makesure you understand the following points and questions:Why are the laws of logic foundational? Laws of Logic (or First Principles of Logic) make discourse possible. If they are not recognized as true, then nothing we claim makes any sense.(pg. 122)List and explain the 3 laws of logic. 1. Law of non-contradiction - something cannot both be and not be at the same time and in the same respect.~(P*~P) - It is not the case there there can be both P and non-P.The logical opposition to black is non-black, not white. No exception to this law. (pg. 122)2. Law of Excluded Middle - something either is or is notP v ~P (Either P or non-P). It excludes the possibility of something in the middle of existence andnonexistence. Something either exists or not. No such thing as half-existing.3. Law of identity - something is what it is.(P=P) - whatever a particular thing is, it is that particular thing (pg. 124)Know the symbolic expression of the law of non-contradiction and how it clears up confusions.~(P*~P) - It is not the case there there can be both P and non-P.It clears it up because the logical opposite of black is not white, but is nonblack, which would include any color, including gray. (pg. 122)Explain the common confusion concerning God and contradictions.Some Christians have challenged this law by claiming that God is omnipotent and therefore can do anything based on Matt. 19:26 that all things are possible with God as proof of their claim.2 problems1. Context of passage is salvation2. When he says "all things are possible with God", it really means "all things that can possibly be are possible with God". Contradictions cannot be. It has nothing to do with omnipotence. Some things by their nature are impossible.(pg. 123)Page 1 of 7PHIL 201Know the symbolic expression of the Law of Excluded Middle. P v ~P (Either P or non-P). It excludes the possibility of something in the middle of existence and nonexistence. Something either exists or not. No such thing as half-existing Why is it called the Law of Excluded Middle? It excludes the possibility of something in the middle of existence and nonexistence. A thing either exists or it does not.No tertian quid (3rd what). Things cannot half exist.(pg. 124)Know the why the laws of logic are self-evident.They prove themselves and do not need any proof outside themselves. (pg. 125)Know the three parts of an argument.Premises Conclusion Inference (pg. 125)Distinguish the language of evaluating arguments (deductive and inductive) from how we evaluate propositions.When it comes to the propositions within the argument, we evaluate them according to their truthvalue, whether they are true or false.Deductive = valid or invalidInductive = strong or weak(pg. 126)Explain the relationship between truth value of the propositions with the validity/strength of the argument.The validity or strength of an argument and the truth value of the propositions are 2 distinct and separate aspects of an argument. The truth value of the propositions in an argument has nothing to do with its validity or strength, and validity or strength has nothing to do with truth value.An argument can be valid or strong with all false propositions, and it can be invalid or weak withall true propositions. (pg. 126)Know the point about agreeing with the conclusion of an argument and it being a good argument.Do not assume that because you agree with the conclusions of an argument it must be a good argument. Be careful about proclaiming that an argument is valid or strong simply because you like its conclusion. (pg. 127)Know the kind of conclusion arrived at by a valid deductive argument. A deductive argument is considered sound when it is valid and the premises are true. A deductive argument must be both valid and feature all true premises. (pg. 127)Note the difference in terminology between the laws of logic and the rules of valid inference.Laws of Logic -Rules of Valid Inference -Page 2 of 7PHIL 201Explain the categorical syllogism (you did not need to memorize the chart nor the 6 rules of validinference). There are 4 and only 4 kinds of categorical propositions. Each has a traditional letter name (A, E, I, O)Categorical syllogism features 3 categorical propositions (major premise, minor premise and conclusion) It also contains 3 terms and only 3 terms, each being used twice. They must conform to the 6 rules of valid inference. (pg. 129-130)Explain the disjunctive syllogism and know the fallacy.Makes use of the disjunctive proposition which is an either/or statement that affirms or denies something in terms of 2 alternatives called alternates. In a valid disjunctive syllogism, one will deny one of these alternatives in the 2nd premise and affirm the other alternant in the conclusion.Fallacy: The fallacy of affirming the alternant (see footnote) - pg. 131 (pg. 130)Explain what a hypothetical proposition is doing and what it is not doing.It employs the hypothetical proposition which is a statement that affirms or denies something in terms of an antecedent, expressed as an "if", and a consequent, expressed as a "then." It is making a promise or guarantee. (pg. 131-132)Explain the hypothetical syllogism and know the two fallacies.If...then...2 basic kinds 1. Pure - uses only hypothetical for 2 premise and conclusion2. Mixed - Uses a hypothetical proposition for the 1st premise, but uses categorial propositions for the 2nd premise and conclusion.2 forms---modus ponens (the way of affirming)--2nd premies affirms that the antecedent of the hypothetical is true---modus


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LIBERTY PHIL 201 - PHIL201_Study_Guide_Lesson_4

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