Logic 1.4 Section 1 & 2

2. The ebb and flow of the tides has been occurring every day for millions of years. But nothing lasts forever. Therefore, probably the motion of the tides will die out within a few years.

This is a prediction. But the prediction is weak. Anything that's been happening for millions of years will likely continue. Weak/Uncogent/TP/PFC

If George Washington was beheaded, then George Washington died. George Washington died. Therefore, George Washington was beheaded.

Any argument having true premises and a false conclusion is invalid, and all invalid arguments are unsound. Invalid/Unsound/TP/FC

11. Every map of the United States shows that Alabama is situated on the Pacific coast. Therefore, Alabama must be a western state.

If you assume that the premise is true, then it is probable that the conclusion is true. But the premise is false. Alabama is not on the Pacific coast. Strong/ uncogent/ FP/ PFC

12. When Neil Armstrong landed on the moon, he left behind a gold plated Schwinn bicycle, which he used to ride around on the moon's surface. Probably that bicycle is still up there on the moon.

Armstrong did not leave behind a gold-plated bicycle. However, assuming he did, the bicycle would most likely still be there. Strong/ Uncogent/ FP/PFC

5. Most popular film stars are millionaires. Shailene Woodley is a popular film star. Therefore, probably Shailene Woodley is a millionaire.

If you assume the premises are true, the conclusion is probably true, so the argument is strong. Strong/Cogent/TP/PTC

3. The vast majority of Rose Bowl games (in Pasadena, California) have been played in freezing-cold weather. Therefore, probably the next Rose Bowl game will be played in freezing-cold weather.

If the premises are assumed true, the conclusion is probably true. So the argument is strong. But the premise is false. Pasadena has a very warm climate. Strong/Uncogent/FP/PFC

10. Coca-Cola is an extremely popular soft drink consumed all over the world. Therefore, probably someone, somewhere, is drinking a Coke right this minute.

If you assume that the premise is true, then it is probable that the conclusion is true. Strong/ Cogent/ TP/ PTC

15. A random sample of twenty-five famous country and western singers, which included Taylor Swift and Blake Shelton, revealed that every single one of them studied music in Tasmania.

If you assume the premise is true, it is probable that the conclusion is true. But the premise is actually false. The listed singers did not study music in Tasmania. Strong/ Uncogent/ FP/ PFC

Since the Department of Defense Building outside Washington, D.C. has the shape of a hexagon, it follows that it has seven sides.

If you assume the premise is true, the conclusion would necessarily be true. But the premise is false. The Department of Defense Building is called "the Pentagon" because it is in the shape of a pentagon (a five sided figure). Invalid/Unsound/FP/FC

All physicians are individuals who have earned degrees in political science, and some lawyers are physicians. Therefore, some lawyers are persons who have earned degrees in political science.

If you assume the premises are true, the conclusion is necessarily true. So the argument is valid. But it is false that all physicians are individuals with degrees in political science. Valid/ Unsound/ FP/TC

The longest river in South America is the Amazon, and the Amazon flows through Brazil. Therefore, the longest river in South America flows through Brazil.

If you assume the premises are true, the conclusion is necessarily true. Thus, the argument is valid. If you do not know the location of the Amazon river, please check a map. Valid/Sound/TP/TC

Since London is north of Paris and south of Edinburgh, it follows that Paris is south of Edinburgh.

If you assume the premises are true, the conclusion is necessarily true. To see this, draw a vertical line with "North" at the top, and situate the three cities on this line. A quick check of a map shows that the premises are true. Valid/Sound/TP/TC

Since Winston Churchill was English, and Winston Churchill was a famous statesman, we may conclude that at least one Englishman was a famous statesman.

If you assume the premises are true, the conclusion would necessarily be true. Also, the premise are true. Thus, the argument is valid and sound. Valid/Sound/TP/TC

If Queen Elizabeth was born in Los Angeles, then she is a California native. Queen Elizabeth is not a California native. Therefore, Queen Elizabeth was not born in Los Angeles.

If you assume the premises are true, the conclusion would necessarily be true. So the argument is valid. Also, the premises are true. Valid/Sound/ TP/TC

Chicago is a city in Michigan and Michigan is part of the United States. Therefore, Chicago is a city in the United States.

If you assume the premises are true, the conclusion would necessarily be true. So the argument is valid. But the first premise is false. Chicago is not in Michigan. Valid/Unsound/FP/TC

The Empire State Building is taller than the Statue of Liberty, and the Statue of Liberty is taller than the Eiffel Tower. Therefore, the Empire State Building is taller than the Eiffel Tower.

If you assume the premises are true, the conclusion would necessarily be true. So the argument is valid. But the second premise is false. The Statue of Liberty (350 ft.) is not taller than the Eiffel Tower (984 ft). Valid/Unsound/FP/TC

Every province in Canada has exactly one city as its capital. Therefore, since there are thirty provinces in Canada, there are thirty provincial capitals.

If you assume the premises are true, the conclusion would necessarily be true. So the argument is valid. But the second premise is false. There are 10 provinces in Canada. Valid/Unsound/ FP/FC

Since Moby Dick was written by Shakespeare, and Moby Dick is a science fiction novel, it follows that Shakespeare wrote a science fiction novel.

If you assume the premises are true, the conclusion would necessarily be true. Thus, the argument is valid. But both premises are false, so the argument is unsound. Valid/UnSound/FP/FC

Since the Spanish-American War occurred before the U.S. Civil War, and the U.S. Civil War occurred after the Korean War, it follows that the Spanish-American War occurred before the Korean War.

If you enter the information of the premises into a time chart, the Spanish American War could have happened either before or after the Korean War. Thus, the argument is invalid. Also, both premises are false. So, the argument is unsound for two reasons. Invalid/Unsound/FP/TC

All leopards with lungs are carnivores. Therefore, all leopards are carnivores.

It's true that all leopards with lungs are carnivores. However, it doesn't follow from this alone that all leopards are carnivores because the premises don't tell us whether all leopards have lungs. Invalid/Unsound/TP/TC

The United States Congress has more members than there are days in the year. Therefore, at least two members of Congress have the same birthday.

Suppose there are 365 congressmen with different birthdays. Set these congressmen aside. The congressmen that remain will have to share birthdays with the 365 that you set aside, because there are no more birthdays left to pick from. Valid/ Sound/ TP/TC

8. Paleontologists have unearthed the fossilized bones of huge reptiles, which we have named dinosaurs. Tests indicate that these bones are more than 50 million years old. Therefore, probably dinosaurs really did roam the earth more than 50 million years ago.

This is a causal inference that moves from effect (fossilized bones) to cause (dinosaurs). If the bones are more than 50 million years old, the dinosaurs must be, too. Strong/Cogent/TP/PTC

6. Constructing the great pyramid at Giza required lifting massive stone blocks to great heights. Probably the ancient Egyptians had some antigravity device to accomplish this feat.

This is a causal inference that moves from effect to cause. It is not reasonable to conclude that the blocks were raised via an antigravity device. Week/Uncogent/ TP/PFC

7. People have been listening to rock and roll music for over a hundred years. Probably people will still be listening to it a year from now.

This is a prediction. Any social movement that has lasted more than one hundred years will probably continue in existence for at least a few more years. Strong/Uncogent/FP/PTC

14. Unlike monkeys, today's humans have feet that are not suited for grasping objects. Therefore, a thousand years from now, probably humans will still have feet that are not suited for grasping objects.

This is a prediction. The structure of the human body is not likely to change in a thousand years. Strong/ Cogent / TP/ PTC

13. Children love green M&M's. But brussels sprouts are green, too. Therefore, it must be the case that children love brussels sprouts.

This is an argument from analogy. Children do love green M&Ms, but they hate brussels sprouts. Weak/ Uncogent/ TP/PFC

4. Franklin Delano Roosevelt said that we have nothing to fear but fear itself. Therefore, people have no reason to fear serial killers.

This is an argument from authority. Roosevelt's statement is misapplied to serial killers. Weak/Uncogent/TP/ PFC

9. The Declaration of Independence says that all men are endowed by their creator with certain unalienable rights. Therefore it probably follows that a creator exists.

This is an argument from authority. The author of the Declaration of Independence is not an authority on the existence of God, nor did he intend that this statement in the Declaration be considered a claim that God exists. Weak/ Uncogent/ TP/UTVOC

1. The grave marker at Arlington National Cemetery says that John F. Kennedy buried there. It must be the case that Kennedy really is buried in that cemetery.

This is an argument from signs. Since you can normally trust what's written on a gravestone about the identity of the person buried there, the argument is strong. Valid, Cogent; TP ; PTC

Since some fruits are green, and some fruits are apples, it follows that some fruits are green apples.

Try modifying the argument but keeping the same form: Some fruits are purple, and some fruits are lemons. Therefore, some fruits are purple lemons. This argument is clearly invalid because it has true premises and a false conclusion. If the reasoning doesn't work for purple lemons, then it doesn't work for green apples. Invalid/Unsound/ TP/TC