Review: What is the difference between a deductive and an inductive argument? What is a valid argument? What is a sound argument? Vs. Arguments inductive argument: argument in which it is improbable that the conclusion be false given that the premises are true. inductive argument: argument in which the conclusion does not follow probably from the premises, even though it is claimed to. Example: All meteorites found to this day have contained gold. Therefore, probably the next meteorite to be found will contain gold. What is the conclusion? What is the premise? If we assume that the premise is true is the conclusion a likely one? Does anyone know if the premise is true or not? 1
Example: When a lighted match is slowly dunked into water, the flame is snuffed out. Gasoline is a liquid, just like water. Therefore, when a lighted match is slowly dinked into gasoline, the flame will be snuffed out. What is the conclusion of this argument? What are the premises? Are the premises true? Is this a strong or weak argument? Why or why not? argument: is a strong inductive argument that has all true premises. argument: is an inductive argument that is weak, has one or more false premises, or both. Inductive arguments have another prerequisite before they can be cogent; it is known as the total requirement, which requires that the premises not leave out any information that would nullify or necessarily change the conclusion. 2
Example: Swimming in the Caribbean is usually lots of fun. Today the water is warm, the surf is gentle, and on this beach there are no dangerous currents. Therefore, it would be fun to go swimming here now. Groups of Nonarguments Deductive Valid Invalid Strong Practice: Determine whether the following arguments are either strong or weak. State whether the premises are true and whether the argument is cogent or uncogent. The grave marker at Arlington National Cemetery says that John F. Kennedy is buried there. It must be the case that Kennedy really is buried in that cemetery. Franklin Delano Roosevelt said that we have nothing to fear but fear itself. Therefore, people have no need to fear drunk drivers. 3
Fallacies of Induction: Appeal to Authority (Argumentum ad Verecundiam) This fallacy occurs when someone appeals to an authority in an argument to provide evidence for their conclusion but the witness lacks credibility. Several reasons they may lack credibility 1. Lack proper 2. or prejudice 3. Motive to or disseminate misinformation 4. Inability to correctly perceive or information Dr. Bradshaw, our family physician, has stated that the creation of muonic atoms of deuterium and titium hold the key to producing a sustained nuclear fusion reaction at room temperature. In view of Dr. Bradshaw s expertise as a physician, we must conclude that this is indeed true. James W. Johnston, Chairman of R. J. Reynolds Tobacco company, testified be for Congress that tobacco is not an addictive substance and that smoking cigarettes does not produce any addiction. Therefore, we should believe him and conclude that smoking does not in fact lead to any addiction. there are some areas in which practically no one can be considered an authority. Such areas include politics, morals and religion. For example, if someone were to argue that abortion is immoral because a certain philosopher or religious leader has said so, the argument would be weak regardless of the authority s qualifications. Many questions in these areas are so hotly contested that there is no conventional wisdom an authority can depend on. Hurley pg. 132. 4
People have been trying to prove for millennia that God does not exist, and no one has been successful. Therefore, we must conclude that God exists. What do you think about this argument? Is it deductive or inductive? What is the conclusion? What are the premises? Is the argument valid, invalid, strong, weak, sound, cogent? Appeal to (Argumentum ad ) Appeal to happens when the premises of an argument state that nothing has been proved one way or the other about something but then the conclusion makes a definite assertion about that subject. People have been trying to prove, for millennia, that God exists. They have been unable to do so. Therefore, we must conclude that God does not exist. 5
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