Practical Reasoning Midterm Study Guide
Practical Reasoning Midterm Study Guide TPHIL 250
University of Washington Tacoma
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This 0 page Study Guide was uploaded by Qihua Wu on Friday November 13, 2015. The Study Guide belongs to TPHIL 250 at University of Washington Tacoma taught by GEE,JERAMY S. in Fall 2015. Since its upload, it has received 49 views. For similar materials see PRACTICAL REASONING (I&S,QSR) in PHIL-Philosophy at University of Washington Tacoma.
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Date Created: 11/13/15
Validity Syntactic The conclusion follows from true premises Semantic It is impossible to have a false conclusion from true premises Soundness The argument is valid and all the premises are true PremiseConclusion Form Different premises support conclusion meaning the premises are independent of each other Premises acting as joint support where the conclusion needs two or more premises to come up to ifthen sentences are examples of two premises supporting one conclusion Premises supporting each other each premise leads to another premise meaning the middle premises are the conclusions for the previous premise and the premise of the latter premise A good way to do this is to rst identify the conclusion then decide the premises sometimes there are sentences for background information but those are not supporting the conclusion therefore are not considered as premises Look for indication words such as quotafter allquot quotthereforequot to help you identify the conclusion Reliability and Unreliability A premise is reliable If it is commonly accepted fact by the intended audience since one premise can be accepted by a group of people but not others If it is supported by appropriate reliable testimony or sources A premise is unreliable If it is widely known as false If it can not be determined whether it is false or not Reliability is not the truth of the premise just because it is not reliable does not make a premise false Common Valid Argument Forms Modus Ponens if p then q p Therefore q Modus Tollens if p then q not q Therefore not p Hypothetical Syllogism If p then q lf q then r Therefore if p then r Valid as long as each premise has form of if then and the consequent of one premise q in if p then q becomes the antecedent of the next q in if q then r Disjunctive Syllogism p or q not p Therefore q Dilemma p or q if p then r if q then t therefore r or t assume the opposite not p Argue Therefore p must Reductio Ad Absurdum to provep from that assumption Conclude q Q is false be true For if then sentences it is important to identify the antecedent and the consequent P if q means if q then p P only if q means if p then q P unless q means if not q then p To easily understand these put these into sentences Invalid Argument Forms Af rming the consequent if p then q q Therefore P Denying the antecedent if p then q not p Therefore not q Undistributed middle middle term is not distributed in at least one of the premises it is easier to see when use Venn diagram An example is P is q R is q Therefore p is r Counterexample to an invalid argument Test its validity by using either truth table or venn diagram you can also use the knowledge of invalid argument forms Symbols of sentential logic v for or amp for and for negation single arrow for conditional sentences if then double arrow for biconditional sentences if and only if You can not have a negation inside the parentheses unless the negation is a part of the premises You have to use 39039 to separate out more than two components that act together Use different letter to represent premises with different meaning and it is better to write down what each letter means for reference when you are trying to represent them with symbols Truth Table amp Interpretation Truth Table Start out with the inner most letter it alternates with T and F use the power of 2 rule the second closest to the premises will alternate between 39IT and FF the third will with llll and FFFF etc After nishing with each letter put on the premises and based on the individual statement determine whether the premises are true or not Continue until you reach a part where there are all true premises but result with a false conclusion then you would have proven the argument is invalid if at the end there is no false conclusion resultant from true premises then the argument is valid Interpretation Start out with assuming the conclusion is false then based on that worked backward if you can have a false conclusion and all premises to be true then the argument is invalid if all the premises are no longer true once you had set the conclusion false then the argument is valid Venn Diagram To draw venn diagram rst identify the subject and predicate terms by looking at the conclusion Then identify the middle term if there is the transition between the subject to the predicate term Draw corresponding circles to each term and make sure the circles intersect Then shade on the circles that do not follow the argument rst work on the major premise premise that contains the predicate term then work on the minor premise premise that contains the subject term After going through the premises look at the remaining unshaded area if it includes nothing as an exception to the conclusion then the argument is valid If the argument consists more than three terms you can use additional venn diagrams to draw the conclusion by making a venn diagram that draws the subconclusion from two premises then use the subconclusion as one premise then add the additional premise to draw the nal conclusion
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