Sep 27, 2006
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- Recap predicate logic proofs
	- define a vocabulary
	- write down sentences in first-order logic
	- write down the goal and negate it
	- convert to clausal form
		- IMPORTANT: Negate before converting to clausal form
	- try to arrive at a contradiction

- More on converting to clausal form
	- removing existential quantifiers
		- Skolem constants
		- Skolem functions
	- apply distributive law to get rid of nested expressions
	- list conjunctions as separate clauses

- Example
	- Using the vocabulary
    		- Man(x): true when x is a man.
    		- Barber(x): true when x is a barber.
    		- Shaves(x,y): true when x shaves y. 
	- Write out the sentence
		- There exists a barber who shaves all those
		  who are not self-shavers.

- Another example (from your book)

- Given
	- Everyone who loves all animals is loved by someone.
	- Anyone who kills an animal is loved by no one.
	- Jack loves all animals.
	- Either Jack or Curiosity killed the cat, who is named Tuna.

- Answer
	- Did Curiosity kill the cat?