F A L L A C I E S

• No proof or validity
• Best that can be said is that the argument is sound or cogent
• Acceptable by a reasonable person
• Based on our natural ability to think in analogy, metaphor, simile, rhyme, etc.

• The universe exhibits a structural design (premise)
• A machine exhibits a structural design (premise)
• A machine is made by an intelligent being
(premise)
• The universe was made by an intelligent being
(conclusion)

• Analogy drawn between universe and machine
• Form of argument is as follows:
• A has the property of C.
• B has the property of C.
• B has the property of D.
• A has the property of D

• We are called to the scene of a murder committed on Tuesday at midnight around Sunset Avenue.
• The murder weapon was a .45, the victim was a derelict alcoholic, and there were a dozen witnesses who saw Jack do it.
• We put out an all-points bulletin on Jack, but he is not apprehended.

• Now suppose that on Wednesday night we are called to the scene of another murder, again committed at midnight on Sunset Avenue.
• The victim is a derelict alcoholic, the murder weapon is a .45, but unfortunately there are no witnesses.

• Tuesday's murder was committed at midnight (T has the property of M)
• Wednesday's murder was committed at midnight (W has the property of M)
• Tuesday's murder took place on Sunset Avenue (T has the property of S)
• Wednesday's murder took place on Sunset Avenue (W has the property of S)
• Tuesday's murder involved a .45 (T has the property of F)
• Wednesday's murder involved a .45 (W has the property of F)
• Tuesday's murder victim was a derelict alcoholic (T has the property of D)
• Wednesday's murder victim was a derelict alcoholic (W has the property of D)
• Tuesday's murder was committed by Jack (T has the property of J)
• Wednesday's murder was committed by Jack (W has the property of J)

• Hasty Generalization
• Reasoning to an unwarranted generalization on too small of a sample.
• Are 4 similarities enough to warrant a 5 th ?
• Not all similarities are alike
• If you have one strong similarity, are the others weak, or stretched just to find more?

• Post Hoc, Ergo Propter Hoc (after this, therefore because of this)
• Can you reason that because B followed A that A is the cause of B?
• Usually occurs when you are “dead sure”, or suspect is included in first premise
• The clincher should be the last premise in your thinking

• Emotional Reasoning
• Words used to persuade?
• “Derelict” in example
• Remain impartial in reasoning!

• Fallacy of Composition
• Inferring that a property of the parts must also be a property of the whole.
• we did not have any witnesses to the murder on Wednesday night.
• If we were to conclude that Jack likes to leave witnesses around whenever he murders somebody, we would be making this fallacy, or reading more into the whole than the parts imply.

• False Dilemma
• Assuming there are only two alternatives, X and Y.
• Occurs when premises are weak
• Exists when you must choose between two undesirable alternatives
• Is there a Z factor (third alternative)?

•
• Affirming the Consequent
• Bottom-up reasoning needs to have hypothesis-testing
• Treat conclusion as a hypothesis, and go back to premises to seek dissimilarities, flaws, or differences that would disconfirm the conclusion
• The obvious flaw is that we have no witnesses to Wednesday's murder, so if we added the logic:
• Tuesday's murder was committed in front of witnesses (If P, then Q)
• Wednesday's murder was not committed in front of witnesses (Q)
• Nevertheless, Tuesday's murder and Wednesday's murder are similar (P)
• We would be affirming the consequent in this case of inductive logic. It is important to try and go back and disconfirm the hypothesis in good faith.