1. Unit 1 – Foundations of Reason and Logic
Section 1 – Reasoning about Reasoning

2. What is Reasoning?
We all have to make decisions about what to believe and how to act
Some of our questions are more personal and practical: ?
Whom should I invite to formal?
What will I do after completing high school?

3. Some questions involve our relationship with other and the world:
Is it right to tell a lie? ?
Why should I conserve energy?

4. Other decisions involve questions that are more philosophical:
Can we truly know anything? ?
Is the a god? .

5. So… What is Reasoning?! .
Given the importance of reasoning we will begin to explore:
The nature of reasoning
Good reasoning from bad
Our limits of reasoning

6. However, reasoning is not just thinking about ourselves
Its about thinking in accordance with standards of reasoning and being on guard against;
in our thinking.

7. Why is good reasoning important?.
More informed, well thought out course of action
$$$ is spent on advertising, which can be manipulative
Help us assess claims made in the media
Identify information that is credible and use it to our benefit
Defend our beliefs and have them hold up scrutiny
Why things are the way they are

8. General Principles of Reasoning.
In his works he identified some general principles of logic and founded a branch of reasoning that we call formal logic
Dedicated to the study of deductive arguments

9. Since his time many philosophers have attempted to build on his ideas by further defining laws of thought that are considered fundamental to the reasoning process
Law of ___________
However, prior to understanding these laws we must first understand __________________

10. Proposition: _________________________________________ _________________________________________
Questions and commands are not propositions because we do not label them true or false
Here are some examples
The room is messy – true sometimes
The shape of the earth is close to the shape of a sphere
The moon is made of cheese – false
5 is a prime number – true always
Capital punishment is never justified – up for debate

11. Law of identity
States that: _________________________________________ _________________________________________
Whatever the thing is, it is what it is and does not have alternate identity or multiple identities
So fundamental to our thinking is the view that something cannot be both what it is and at the same time and in the same respect, other than what it is

12. Law of non-contradiction
States that: _________________________________________ _________________________________________ _________________________________________
Thus contradiction occurs when a proposition is held to be both true and false
Example
If you believe, today is Wednesday and today is not Wednesday at the same time (eastern standard) and in the same respect (not today is Wednesday but it feels like Tuesday) then you hold a contradiction.

13. Law of the excluded middle
States that: _________________________________________ _________________________________________ _________________________________________
Example
“It is raining.” Depends on the time and place to which we are referring.
Thus the proposition may be true on July 23 in Toronto but not in Montreal or on July 23 but not on July 24
It is either raining or its not – there is no middle ground

14. Recap Using the example of a pencil, the laws work in this way:
This pencil (A) must be this pencil (A)--in philosophical terms, this is called a tautology, which is something which is true by definition
If this is a pencil (A), it cannot also not be a pencil (not A) at the same time
It is either true that this thing is a pencil or it is not true that this thing is a pencil. It can't be a little bit true and a little bit false

15. The Principles of Sufficient Reason
States that: _________________________________________ _________________________________________
There are several different versions of this principle
For every entity X, if X exists, then there is a sufficient explanation for why X exists
For every event E, if E occurs, then there is a sufficient explanation for why E occurs
For every proposition P, if P is true, then there is sufficient explanation for why P is true

16. Ockham’s Razor
Ockham stated that: _________________________________________ _________________________________________
Example
You tell your teacher you don’t have your textbook because aliens took it and they went back home
Your teacher is faced with two choices
Believe or not
Based on Ockham’s razor your teacher will reject choice 2 based on reasoning that your lose can be explained without aliens – that is, without adding entities (aliens beyond necessity)