PSC404, Spring 2001
Answers to Assignment 1
Critical thinking

      1. In addition to fact and prove, another common word that is often misused is control. In each of the sentences below, explain what control or its derivative means. (You will probably need to consult your dictionary.)
a. One of the main techniques of scientific research is controlled experiments. “Checked” experiments, in which the variable creating the effect being investigated is identified by carefully changing one variable at a time.
b. I carefully controlled the conditions of my experiment. I made sure that my experiment was run exactly as I wanted it to be run.
c. He is the controller of the university. He regulates the university’s financial affairs.
d. Control your rage! Hold back your rage!
e. When arriving in Brussels, turn left as soon as you exit from Passport Control. The place where passports are checked, not where they are regulated.

      2. “After deliberating for 16 hours spread over three days, the jury found the defendant guilty of embezzling $100,000 from the small post office where she worked.” What did the jury’s verdict really mean? How does this relate to our thinking about the JFK assassination? The jury chose to believe that the defendant was guilty, based on evidence that was almost certainly less than conclusive. It helps us to discriminate between answers that are solid and those that are to some degree guesses.

      3. Person 1: “The Mafia killed Kennedy.” Person 2: “You’re crazy. He had nothing to do with it.” What is the logical weakness(es) in this dialogue, and how could we alter it in order to bring meaning to it? The logical weakness is that both discussants are simply stating their conclusions (beliefs) rather than giving reasons for them. One cannot properly counter one conclusion simply by stating another. To improve the dialogue, the first person must give his reasons for his conclusion. If the second person disagrees with him, the latter must respond by showing why the first person is wrong and then stating his conclusion and the reason(s) for it.

      4. Explain the act of believing in terms of probabilities. Believing is choosing to accept a proposition as true (probability of 100%) even though we know that the evidence for it is inconclusive (probability <100%). Why do humans believe things? Because the animal/emotional side of ourselves is not prepared to hold things in suspension for long. We are programmed to decide questions and move on.

      5. Here are ten examples of evidence from the JFK case. For each, list whether it is testimonial or physical, direct or indirect (with respect to who killed JFK), and testable or untestable.
a. “Earwitness” reports by nearly 100 persons in Dealey Plaza who heard shots fired from the grassy knoll. Testimonial, indirect, untestable. (We may be able to test whether shots were fired from the knoll, but we can’t test what each witness heard.)
b. Bullet fragments recovered from the scene that were traced ballistically to only one rifle. Physical (the bullets plus the act of tracing), indirect to the shooter but direct to the rifle, testable.
c. The Mannlicher-Carcano rifle owned by Lee Harvey Oswald and allegedly fired by him. Physical (the rifle plus the proof that he owned it), indirect to the killer but direct to the owner, testable.
d. The X-rays of Kennedy’s head, taken during the autopsy, that show lead fragments coning outward from the small hole in the back to the large hole in the right front, as evidence for hit from rear. Physical (the X-rays and their interpretation), direct, testable (the interpretation of the coning).
e. Howard Brennan’s report of seeing the final shot fired from the Texas School Book Depository, plus his description of the shooter. Testimonial, direct for the killer, untestable.
f. Julia Mercer’s report of seeing a man carrying a rifle to the grassy knoll an hour before the assassination, as evidence for a shooter on the knoll. Testimonial, indirect for a shooter from the knoll but direct for someone carrying a rifle there, untestable.
g. The footprints found in the mud behind the picket fence on the grassy knoll by James L. Simmons, as evidence of shooter on the knoll. Testimonial (unless someone photographed the footprints), indirect for a shooter there but direct for someone standing there, untestable (his memory).
h. The Cuban exiles’ anger over the failed Bay of Pigs invasion as reason for them to kill Kennedy. Testimonial, direct (a legitimate reason for some of them to want JFK dead), untestable (they say that’s their reason, but is it really?).
i. Kennedy’s dual motions after the head shot, as shown by the Zapruder film, as evidence for direction of final shot. Physical, indirect (close call—may also be considered direct), testable (to see if there were other possible reasons for the motions).
j. Reports by the three men on the fifth floor of the Depository, who heard a rifle being fired directly above them. Testimonial, indirect to the killer but direct to the location of the shots, untestable.

      6. Here are ten characteristics of Dealey Plaza during and after the assassination. Explain how each would have affected the ability of eyewitnesses to perceive and record the events and later describe them.
a. The shots came unexpectedly. Will weaken the witnesses’ ability to perceive them properly.
b. The shots came from a direction or directions that were difficult to determine because the plaza was ringed by tall buildings and other structures that created complex echoes. Will weaken the witnesses’ ability to associate the proper direction(s) with them.
c. The crowd in the plaza must have thought that it was being fired upon. Fear for personal safety would have weakened the witnesses’ ability to perceive and remember details about the shots. They would first have tried to protect themselves.
d. Panic ensued, and some witnesses dropped to the ground instinctively. Would also have disrupted their ability to perceive and remember properties of the shots.
e. The whole thing was over in a matter of seconds and the motorcade sped away to Parkland Memorial Hospital. The shortness of the event would have made it harder to remember details. The motorcade’s speeding away would have distracted the witnesses’ attention in the critical first few moments when they could have been organizing their memories of the shots.
f. The Dallas police immediately began searching the area and the nearby buildings. The confusion associated with the search, coming so soon after the shots, would also have worked to confuse their memories.
g. The Dallas police began questioning people and taking statements within minutes. The questions soon after the event would have helped the witnesses organize their thoughts in the relatively early stages.
h. People compared impressions and tried to determine what had just happened. Would have induced some witnesses to agree with the “group.”
i. Everyone knew that their president, their governor, and/or their vice president had been fired upon. Would have added to the stress of the event and therefore would have made it harder to remember the events.
j. The whole event was set against the backdrop of the height of the Cold War. Natural fears of this being the opening salvo of something potentially much larger would have increased the stress and made the events more difficult to remember properly.
Summary: 9 of 10 factors were unfavorable for witnesses’ remembering the events accurately. No wonder the actual accounts varied so much!

      7. (a) Why are working hypotheses so important to thinking critically about the JFK assassination? Because they allow us to use the best available evidence as a preliminary, tentative conclusion, i.e., we don’t have to have conclusive evidence in order to reach some idea about what happened. They also allow us to approach the answer in a stepwise, progressive fashion. (b) Define falsifiability and explain how we use it to help us understand the JFK assassination. Falsifiability is the property of an assertion that allows it to be disproved objectively. Important to the JFK assassination because it provides a criterion for rejecting hypotheses that won’t get us anywhere.

      8. Define “Occam’s Razor” and tell why it is so important to understanding the JFK assassination. “Occam’s razor,” or the “Principle of Parsimony,” states that we must always consider first the simplest hypothesis consistent with all the reliable evidence. Important because it weeds out the many hypotheses with components that don’t directly relate to evidence concerning the assassination.

      9. Describe the similarities and dissimilarities between the legal method and the critical (logical) method of evaluating evidence. Both methods formulate the question, try multiple hypotheses, begin with physical evidence, use working hypotheses, and consider testimonial evidence as deemed appropriate. The legal method tends to evaluate hypotheses one at a time, whereas the critical method considers them jointly at the beginning. The legal method lists evidence before hypothesis; the critical method does the reverse. The legal method doesn’t go out of its way to challenge its working hypothesis with new evidence; the critical method does. What is the major message we derive from the table that compares the two? That the methods are far more similar than different. This means that they both are capturing a universal core method for properly dealing with evidence.

      10. (a) Explain the differences between testable, reliable, and unreliable evidence. Testable evidence can be tested objectively (falsified). Reliable evidence has been tested and has passed. Unreliable evidence cannot be falsified. (b) Why is it so important to purge unreliable evidence from our thinking about the assassination? Because unreliable evidence leads inevitably to unreliable conclusions, and none of us want that.

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