LogicThis Web site provides, through a range of materials and tools, an introduction to thestudy of elementary logic covering propositional and predicate calculus. It is aimedespecially at first year undergraduates studying Philosophy at the University ofOxford, but it is hoped that the site may be useful more widely, for anyone whowould like to investigate the subject."Elementary, my dearWatson."Unless otherwise noted all content comes from: http://logic.philosophy.ox.ac.uk/
ConsistentInconsistent(Not contradictoryContradictory) Peter believes that Mary is a woman and that she hasthree hundred children. Peter believes that David has three daughters and foursons, and Davidhas six children in all. Peter believes that David has exactly four children, thatDavidssister is Mary and that Marys only brother hasthree children. Men have children. Peter is a man. Peter has children. Men have children. Peter is a man. Peter does not havechildren.
LexicalAmbiguityStructuralAmbiguityLexical "You know, somebodyactually complimented meon my driving today. Theyleft a little note on thewindscreen; it said, ParkingFine." So that was nice." "Outside of a dog, a book isa mans best friend; insideits too hard to read." The Rabbi married my sister. She is looking for a match.Structural The professor said onMonday he would give anexam. The chicken is ready to eat. Visiting relatives can beboring. The burglar threatened thestudent with a knifehttp://grammar.about.com/od/il/g/lexicalambiguityterm.htm http://grammar.about.com/od/rs/g/syntacticambiguityterm.htm
ArgumentsAn argument consists of a conclusion (which is what is being argued for) anda premise or premises which are the considerations which are being offered infavour of the conclusion.For example:Socrates is a man. All men are mortal. So, Socrates is mortal.The premises of this argument are, of course, "Socrates is a man" and "All men aremortal" and the conclusion is "Socrates is mortal".Note: the conclusion of an argument need not come at the end. It might come at thebeginning, as in:Socrates is mortal. For all men are mortal, and he is a man.Or in the middle, as in:Socrates is a man. So, he is mortal. For all men are mortal.
Arguments1. John will come to the party, because he has been invited, and he likes parties.2. John doesnt like parties. So he will come to the party because he has beeninvited. For he always accepts invitations.3. Mary says that Manchester United will beat Derby County. So , since she isalways right about such things, they will.4. Mary says that Manchester United will beat Derby County. So, if she is rightabout such things, they will.Identify the premises (2)and conclusion (1).
Validity An argument is valid just if it would be impossible for itspremises all to be true and its conclusion false simultaneously. In a valid argument, there is no need for the premises to betrue. (One may want the premises of ones argument to be true;but their not being true does not affect itsvalidity. All dogs go to Heaven. Dingo is a dog. Dingo will go to Heaven. All people are dumb. Sam is a person. Sam is smart.
Validity Either The Patriots or the Philadelphia Eagles will win the Superbowl.The Patriots lost.Therefore The Eagles won. Michael J Fox has Parkinsons disease.Michael J Fox is a vegetarian.To be healthy one should eat meat.http://kslinker.com/VALID-AND-INVALID-ARGUMENTS.html