Directions: Complete this worksheet to demonstrate your understanding of the logic.
Logic is an organized body of knowledge that evaluates arguments.
Argument is group of statements, one or more of which (the premises) are claimed to provide support for one of the others (the
conclusion).
A statement is sentence that is either true or false, typically a declarative sentence or sentence component that could stand as a
declarative sentence, such as:
Politicians always tell the truth.
Ice cream is loaded with calories.
Steph Curry plays basketball.
Premise s are statements that set for reasons or evidence. Premises usually start with a premise indicator, such as:
For
As
Since
Given that
Because
Owing to
Seeing that
As indicated by
A conclusion is a statement that the evidence is claimed to support or imply; the statement that is claimed to follow from the
premises. Conclusions usually start with a conclusion indicator, such as:
Therefore
We may infer
Thus
Hence
Consequently
Implies that
For this reason
As a result
Syllogism is an argument in which a conclusion is drawn (whether validly or not) from two given or assumed premises, each of
which shares a term with the conclusion, and shares a common or middle term not present in the conclusion.
Valid argument is when the conclusion is a logical conclusion of the premises - but the premises might not be true.
Sound argument is when the premises are true and the conclusion is a logical conclusion of the premises.
Example of a valid argument:
Some film stars are women. (premise)
Brad Pitt is a film star. (premise)
Therefore, Brad Pitt is a woman. (conclusion)
Example of a sound argument:
All film stars are celebrities. (premise)
Jennifer Lawrence is a film star. (premise)
Therefore, Jennifer Lawrence is a celebrity. (conclusion)
Information adapted from Hurley, Patrick J. A Concise Introduction to Logic (9th Edition). Wadsworth Publishing, 2004
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Practice
Practice: Read the following arguments and identify the premises and conclusion. Please
note that the conclusion might not necessarily come at the end. For example:
Cats with long hair shed all over the house so you should not get a long-haired cat. I have
heard that they also have lots of fleas.
P1:
P2:
C:
Long-haired cats shed all over the house.
Long-haired cats have fleas.
You should not get a long-haired cat.
Now try to identify the premises and conclusion for the following examples.
The first premise will be identified with P1, the second premise with P2, and the conclusion
with C.
1. Since the auto market is depressed and interest rates are low, it's a good time to buy a
car.
P1: The auto market is depressed.
P2: The auto market interest rates are low.
C: Now is a good time to go and buy a car.
2. The U.S. should refuse to deal with the present North Korean government. North Korea is
guilty of extreme human rights abuses. Further, they refuse to implement democratic
reforms.
P1: North Korea is guilty of extreme human rights abuses.
P2: North Korea also refuses to implement democratic reforms.
C: The U.S. should refuse to deal with the present North Korean government.
3. Cynthia is one year old. Most one-year-olds can walk. It follows that Cynthia can walk.
P1: Cynthia is one-year-old.
P2: Most one-year-olds can walk.
C: So it follows that Cynthia can walk.
On the previous page, you learned the difference between a valid argument and a sound
argument. Please provide your own example of each:
1. Valid argument example:
P1: Most pop singers are females.
P2: Justin Timberlake is a pop singer.
C: Therefore, Justin Timberlake is a female.
2. Sound argument example:
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P1: All pop singers are famous.
P2: Justin Bieber is a pop singer.
C: Therefore, Justin Bieber is famous.
Examples adapted from University of Kentucky Introduction to Logic.
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