ARGUMENT STRUCTURE IN-CLASS EXERCISES

 

For each of the following, identify the premise and conclusion indicators if any are present, diagram the argument and supply any missing premises. If there is no argument, indicate that there is none. (Exercises adapted from Nolt’s Logic.)

 

Example:

[1] One cannot doubt that the car is sputtering [2] and the engine light is on. [3] It follows that, the car needs repaired.

Answer: “One cannot doubt that” (premise indicator), “it follows that” (conclusion indicator), 1 → 3 and 2 → 3

 

(1) [1] We can conclude that you should do well, [2] because you have talent [3] and you are a hard worker.

 

(2) [1] It is a fact that she promised to marry him, [2] and so that's just what she should do. [3] So if she backs out, she's definitely in the wrong.

 

(3) [1] We need more morphine. [2] The reason is that we've got 32 casualties and [3] only 12 doses of morphine left.

 

(4) [1] I can't help you if I don't know what's wrong—[2] and I just don't know what's wrong.

 

(5) [1] If wishes were horses, [2] then beggars would ride.

 

(6) [1] If there had been a speed trap back there, it would have shown up on this radar detector, [2] but none did.

 

(7) [1] The earth is approximately 93 million miles from the sun. [2] The moon is about 250,000 miles from the earth. [3] This means that the moon is about 250,000 miles closer to the sun than the earth is.

 

(8) [1] She bolted from the room [2] and then suddenly we heard a terrifying scream.

 

(9) [1] I followed the recipe on the box, [2] but the dessert tasted awful. [3] This being so, some of the ingredients must have been contaminated.

 

(10) [1] Hitler rose to power because the Allies had crushed the German economy after World War I. [2] From this we can infer that if the Allies had helped to rebuild the German economy instead of crushing it, they would never have had to deal with Hitler.

 

(11) [1] [The apostle Paul's] father was a Pharisee.... [2] He [Paul] did not receive a classical education, for [3] no Pharisee would have permitted such outright Hellenism in his son, and [4] no man with Greek training would have written the bad Greek of the Epistles. (Will Durant, The Story of Civilization)

 

(12) [1] The contestants will be judged in accordance with four criteria: beauty, poise, intelligence, and artistic creativity. [2] The winner will receive $50,000 [3] and a scholarship to attend the college of her choice.

 

(13) [1] Capital punishment is not a deterrent to crime. [2] The reason is that, in those states which have abolished the death penalty, the rate of incidence for serious crimes is actually lower than in those which have retained it. [3] Besides, capital punishment is a barbaric practice, one which has no place in any society which calls itself "civilized."

 

(14) [1] Parents who were abused as children are themselves more often violent with their own children than parents who were not abused. [2] This proves that being abused as a child leads to further abuse of the next generation. [3] Therefore the only way to stop the cycle of child abuse is to provide treatment for abused children before they themselves become parents and perpetuate this sad and dangerous problem.

 

(15) [1] The Bensons must be home. [2] Their front door is open, [3] their car is in the driveway, and [4] their television is on since [5] I can see its glow through the window.

 

(16) [1] The check is void unless it is cashed within 30 days. [2] The date on the check is September 2, and [3] it is now October 8. Therefore, [4] the check is now void. [5] You cannot cash a check which is void. [6] So you cannot cash this one.

 

 

Answers:

(1) “We can conclude that” (conclusion indicator), “because” (premise indicator) (2 → 1) and (3 → 1)

(2) “It is a fact that” (conclusion indicator), “so” (premise indicator) 1 → 2 → 3

(3) “The reason is that” (premise indicator) 2 + 3 |→ 1

(4) 1 + 2 |→ 3 (3 is implied: I can’t help you)

(5) No argument

(6) 1 + 2 |→ 3 (3 is implied: there is no speed trap back there)

(7) “This means that” (conclusion indicator) 1+ 2 |→ 3

(8) No argument

(9) “This being so” (conclusion indicator) 1 + 2 + 4 |→ 3 (4 is implied: the recipe is a good one)

(10) “From this we can infer that” (conclusion indicator) 1 → 2

(11) (1 + 3 |→ 2) and (4 → 2)

(12) No argument

(13) “The reason is that” (premise indicator) 2 → 1 → 4 and 3 → 4 (4 is implied: capital punishment should be abolished)

(14) 1 → 2 → 3

(15) “It’s logical to conclude that” (conclusion indicator) (5 → 4 → 1) and (3 → 1) and (2 → 1)

(16) 1 + 2 + 3 → 4 + 5 → 6