1. NOTE: To change the image on this slide, select the picture and delete it. Then click the Pictures icon in the placeholder to insert your own image. FOUNDATIONS OF REASON & LOGIC Chapter 1

2. Our expectations: You will be able to:  Demonstrate your understanding of philosophical reasoning & critical thinking skills  Identifying & avoiding common fallacies of reasoning  Apply those skills in various contexts

3. What does it mean to be rational? Being able to:  Articulate why you think something is true  Justify your beliefs  Give reasons supporting your answers to fundamental questions If you can’t give a reason, at least give a reason why you cannot. REASONING IS CENTRAL TO PHILOSOPHICAL DEBATE & INQUIRY

4. Have you ever heard of Sherlock Holmes?  For what skill is he famous? (What does he call himself?)  Deductive reasoning (Master of Deduction) But, is that what he really does? We’ll need to discuss terms like:  Reasoning  Deduction  Induction  Abduction IMHO: The authors are big teases! They ask these questions on page 20, but don’t get to the answers / ideas until page 30!

5. What is reasoning?  It’s all pervasive:  We are constantly reassessing our ideas, assessing the merits of others  Reasoning is not just “thinking for ourselves”  We can be “sloppy”  Reasoning is about thinking in accordance with standards of reasoning, being aware of biases, prejudices, stereotypes  It’s related to autonomy  Mastering our thoughts & behaviours

6. Good Reasoning is Important, since it helps:  us make decisions  avoid being manipulated  determine the validity of information, and use it effectively  us defend our positions  us make sense of our world

7. General Principles of Reasoning  Aristotle one of earliest to examine reasoning  In Organon (it means “instrument”) he identifies principles of what we call FORMAL LOGIC  Formal Logic: DEDUCTIVE arguments  Helps us to identify VALID arguments, and faulty ones (ch.3)

8. Other “laws” of reasoning  Law of identity  Law of non-contradiction  Law of the excluded middle  To describe these laws:  we need to know what a proposition is

9. Propositions:  A proposition: a statement that declares something about something else  Either true or false  Questions / commands are not propositions  Examples of Propositions:  Your room is messy.  The moon is made of cheese.  The number 5 is a prime number.  Some BR students are Leaders in Black.

10. The Law of Identity  A is A.  E.g., a dog is a dog. A dog is not a cat.  Identity of a thing deals with the actual properties that the thing possesses, and without which, would not be that thing.  “If a thing did not have an identity and was not identical to itself, then it would be unintelligible. We could not understand it in order to talk about it.”

11. The Law of Non-Contradiction  A proposition cannot be true and false at the same time in the same respect.  CONTRADICTION occurs when something is held to be both true and false at the same time and in the same respect.

12. Law of the Excluded Middle  A specific proposition is either true or false.  There is no middle ground, such as sort of true or neither true or false.

13. Principle of Sufficient Reason  Everything must have a reason or cause.  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 a sufficient explanation for why P is true.  The rationalist philosopher Gottfried Leibniz (1646-1716) stated it explicitly.  Anaximander (612-545 BCE) used it implicitly

14. Ockham’s Razor  After William of Ockham (1287-1347) a Franciscan friar and logician  “we should avoid multiplying entities beyond necessity”  i.e. the simplest explanation or theory is the best choice  Uses fewest assumptions, fewest entities to explain the same facts  But, if the simplest theory doesn’t work: use a more complicated one!