Philosophy 100, Fall 2006					

Idealism Handout 1



Idealism: Everything that exists is either an immaterial mind or is "in" an immaterial mind---a thought, a mental representation, or a sensation.

Realism: There are things other than immaterial minds and the things "in" those minds.



Definition:	X correctly perceives Y's color =df. Y really has the color it 
			appears to X to have.




An Argument based on the case of Larry and his Parakeet:

Part 1:


	1.	Either Larry or his parakeet fails to correctly perceive the thing's 
		color.

	2.	If either Larry or his parakeet fails to correctly perceive the thing's 
		color, then both Larry and his parakeet fail to correctly perceive the 
		thing's color.

	3.	If both Larry and his parakeet fail to correctly perceive the thing's 
		color, then no one ever correctly perceives the color of anything that 
		exists outside the mind.

	4.	Therefore, no one ever correctly perceives the color of anything that 
		exists outside the mind.
		
	
Part 2:

	
	1.	If things outside the mind are colored, then it is not the case that (no 
		one ever correctly perceives the color of anything that exists outside 
		the mind). 

	2.	No one ever correctly perceives the color of anything that exists 
		outside the mind.

	3.	Therefore, things outside the mind are not colored.
	
	

Definition:	X correctly perceives Y's size and shape =df. Y really has the size 
			and shape that it appears to X to have.
	
	
	
An Argument based on the size and shape variation scenario:

	
	1.	Either Larry or the spider fails to correctly perceive the fly's size 
		and shape.

	2.	If either Larry or the spider fails to correctly perceive the fly's size 
		and shape, then both Larry and the spider fail to correctly perceive 
		the fly's size and shape.

	3.	If both Larry and the spider fail to correctly perceive the fly's size 
		and shape, then no one ever correctly perceives the size and shape of 
		anything that exists outside the mind.

	4. 	Therefore, no one ever correctly perceives the size and shape of 
		anything that exists outside the mind.



A General Form of Argument for Idealism, revised:


	1.	If Realism is true, then we know very little about ordinary things (like 
		tables, chairs, tulips...).

	2.	It is not the case that we know very little about ordinary things.

	3.	Therefore, Realism is false.