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PHL (100)
Chapter

Notes simplified from the textbook!


Department
Philosophy
Course Code
PHL201H1
Professor
Brian Baigrie

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[PHL 201: LOGICAL TOOLKIT LECTURE 1 ]
1
LOGICAL TOOLKIT
LOGIC AND PHILOSOPHY
1. Philosophy is about asking questions (does God exist? What can we know?)
2. Since not everyone is going to agree on the correct answers to these questions,
it is extremely important to give reasons WHY you think one answer is better
than another!
3. In the process of giving reasons, you are doing what we call as logical
thinking.
4. Logic is just another way to articulate clearly of your reasons
5. If we want to persuade someone of our reasons, we must think logically for
them to believe our position
ARGUMENTS
1. Argument is not just some verbal dispute
2. An argument is a series of statements where the last statement supposedly
‘follows from, or supported by’ the first statements
3. The last statement is called the conclusion
4. The first statements are called as premises
5. For example:
a.Everyone who lives in Los Angeles lives in California
b. Alvin lives in Los Angeles
c.Therefore, Alvin lives in California
i.First, we know that Alvin lives in Los Angeles
ii.Second, we know that Los Angeles is in California
iii.So, anyone who lives in Los Angeles automatically lives in
California
iv. In this example, if you were to accept the two premises, you
would have to accept the conclusion
v. This is a good argument.
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2[Type text]
VALIDITY
1. There are some arguments with conclusions that dont actually follow from the
premises, even though they supposedly do
2. There are valid and invalid arguments
3. VALID ARGUMENTS:
a.It is valid if the conclusion supported by its premises
b. If the premises were true, then its conclusion would HAVE be true
c.For example, the previous argument of Alvin living in California
4. INVALID ARGUMENTS:
a.Everyone who lives in Los Angeles lives in California
b. Alvin lives in California
c.Therefore, Alvin lives in Los Angeles
i.This is not a valid argument
ii.Premise 1 is true
iii.Premise 2 could be true
iv. The conclusion is false (because Alvin could live in San
Francisco, for instance)
v. The conclusion does not follow the premises
SOUNDNESS
1. Even though sometimes we succeed in putting forth valid arguments, we
sometimes want our premises to actually be true
2. Sometimes we dont know whether our premises is actually true
3. An argument is SOUND if its valid and has all true premises or:
a.It must be valid
b. All of its premises are true
4. For example:
a.Abortion is the killing of an innocent person
b. Killing innocent people is morally objectionable (horrible)
c.Therefore, abortion is morally objectionable
i.Is it valid? It is sound?
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