We will often attempt to provide definitions for key philosophical terms.  For example, we'll be discussing how to define "knowledge," starting on 8/26, and "free will" and "God" later in the semester.

A philosophical definition is much more analytical and precise than a dictionary definition.  What we aim for, in a philosophical definition, is to state a set of necessary and sufficient conditions.  Here's what a definition looks like, using a not-very-interesting concept (bachelor) as an example.

To confirm a definition, it's useful to come up with confirming examples.  For this definition, Ryan Lochte, the swimmer, is a confirming example--he is a bachelor and he meets all of the conditions.  

To challenge a definition, you want to come up with counterexamples.  A counterexample can show one or more of the conditions isn't necessary (type 1).  Another sort of counterexample can show that the conditions aren't jointly sufficient (type 2).  Study the diagram above to understand the difference. Can you think of any type 1 counterexamples to the definition above?  Can you think of any type 2 counterexamples?

Now let's try to define something more interesting:  knowledge!  The reading assignment for 8/26 will prepare you to think about this.  Rosen 99-101 discusses different kinds of knowledge and explains the classic definition of knowledge as justified true belief.  That definition is depicted below.  (Also read Plato, 103-107), though that reading is less relevant to the homework.)

Once you've finished the reading, the homework (due 8/26) is to discuss whether each of the three conditions in the definition above is really necessary for knowing that p. In other words, are there any type 1 counterexamples to this definition?  Can you think of a scenario in which somebody knows some proposition, but they don't believe it, or it's not true, or the person lacks justification for believing it?    

To present your counterexample, describe the scenario and the proposition involved.  Try to make a convincing case that the person does know that p, but doesn't meet one of the three conditions.

ARGUMENTS (8/24, Rosen 1069-1076)
  1. What is an argument?
  2. Deductive vs. inductive arguments
  3. Evaluating deductive arguments
  4. Exercise
  5. Reconstructing arguments
1. What is an argument?
  • fights, debates, involving multiple people
  • controversial claims
  • sequence of statements meant to support a conclusion (this is what we'll mean)

2.  Deductive vs. inductive arguments

  • Deductive arguments: demonstration, proof (e.g. the Socrates argument)
  • Inductive arguments: merely some support for the conclusion (e.g. the lottery argument)
  • Most philosophical arguments are deductive, but we will encounter some inductive arguments later in this course.
3. Evaluating deductive arguments

  1. VALIDITY: an argument is valid when it's impossible for the premises to be true and the conclusion false.  In other words, if the premises were true, the conclusion would also have to be true.
  2. SOUNDNESS: an argument is sound when it's both valid and the premises are actually true.
Note:  in ordinary English, we don't use the words "valid" and "sound" this way.  These are technical terms in philosophy.
Some argument forms are always valid (so, formally valid) or always invalid (so, formally invalid).  Here are some examples: 

More examples contrasting MODUS TOLLENS (valid) with AFFIRMING THE CONSEQUENT (invalid):

4. Exercise from Rosen 1073-1074 (spot the valid arguments)

[i] is valid (modus tollens)
We will talk about the rest on 8/26.

5.  Reconstructing arguments--when we read a philosopher, we will often have to work on extracting and reconstructing the argument they're making.  After we extract it, our next task will be to evaluate whether it's valid and/or sound.

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