THE ARGUMENT FROM ILLUSION
(1) S’pose you are hallucinating a pink rat.
(2) Then you must be seeing something.
(3) But what you see corresponds to no external material object.
(4) Rather, it must be an internal, immaterial object. (a "sense datum")
(5) But your experience is the same as it would be, if you were really looking at a pink rat.
(6) So what it is that you see is the same in each case.
(7) So what it is when you are really looking at something (e.g., a pink rat), all you ever really see are immaterial sense data.
Q.E.D.
(8) It follows that you must infer the existence of an external, material world from your sense data.
IDEALISM (Berkeley):
(9) One cannot justifiably infer the existence of an external, material world from sense data.
(All the properties we normally attribute to an external world are really just the properties of sense data.)
(10) So there is no justification for believing in an external, material world.
(11) Instead, all of our statements about things in an external world should be reconceived as statements about bundles of sense-data.
-- (A "sceptical solution")
Bertrand Russell: You are entitled to believe in the existence of an external, material world after all, because of the durability, persistence, and inter-subjective character of sense-data.
THE ARGUMENT FROM ANALOGY
The Argument:
(1) Much of our own behavior is directed by conscious thought and planning.
(2) We observe similar behavior in others.
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(3) We can infer that their behavior is also directed by conscious thought and planning.
Objections:
à
Why think that the analogy holds? Computers, robots, and the like might be able to do things that, in our case, requires conscious thought and planning. Yet despite the fact that they "behave like we do," we might not be tempted to think that those things have minds of their own.à
Why be sure of premise (1)? Indeed, some of this behavior in others seems to have physical (neural) causes. Why couldn’t we turn the argument around and conclude that our own behavior is "simply" caused by complex physical events?
Skepticism about other minds:
(1) All the evidence we have to infer the existence of other minds is others’ observable behavior.
(2) This observable behavior isn’t sufficient to infer the existence of other minds.
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(3) So we don’t have good reason to believe in the existence of other minds.
Logical Behaviorism (Ryle): A "skeptical solution" to the worry:
All talk about mental states and activity is to be translated into talk about observable behavioral dispositions.