by Mr Erickson » Wed Feb 22, 2012 10:49 am
Nicely put Sab the moment people start claiming reality is how it is because their senses tell them so means they are lost in the logical fallacy of circular argument and at that point I show them the statement made by Professor Thomas Nagel it normally helps them:
If you think about it, the inside of your own mind is the only thing you can be sure of.
Whatever you believe - whether it's about the sun, moon, and stars, the house and
neighborhood in which you live, history, science, other people, even the existence of
your own body - is based on your experiences and thoughts, feelings and sense
impressions. That's all you have to go on directly, whether you see the book in your
hands, or feel the floor under your feet, or remember that George Washington was the
first president of the United States, or that water is H2O. Everything else is farther
away from you than your inner experiences and thoughts, and reaches you only
through them Ordinarily you have no doubts about the existence of the floor under your feet, or the tree outside the window, or your own teeth. In fact most of the time you don't even
think about the mental states that make you aware of those things: you seem to be
aware of them directly. But how do you know they really exist?
If you try to argue that there must be an external physical world, because you
wouldn’t see buildings, people or stars unless there were things out there that reflected
or shed light into your eyes and caused your visual experiences, the reply is obvious:
How do you know that? It’s just another claim about the external world and your
relation to it, and has to be based on the evidence of your senses. But you can rely on
that specific evidence about how visual expereicnes are caused only if you can already
rely in general on the contents of your mind to tell you about the external world. And
that is exactly what has been called into question. If you try to prove the reliability of
your impressions by appealing to your impressions, you're arguing in a circle and
won't get anywhere.
Would things seem any different to you if in fact all these things existed only in your
mind - if everything you took to be the real world outside was just a giant dream or
hallucination, from which you will never wake up? If it were like that, then of course
you couldn't wake up, as you can from a dream, because it would mean there was no
"real: world to wake up into. So it wouldn't be exactly like a normal dream or
hallucination. As we usually think of dreams, they go on in the minds of people who
are actually lying in a real bed in a real house, even if in the dream they are running
away from a homicidal lawnmower through the streets of Kansas City. We also
assume that normal dreams depend on what is happening in the dreamer's brain while
he sleeps.
But couldn't all your experiences be like a giant dream with no external world outside
it? How can you know that isn't what's going on? If all your experience were a dream
with nothing outside, then any evidence you tried to use to prove to yourself that there
was an outside world would just be part of the dream. If you knocked on the table or
pinched yourself, you would hear the knock and feel the pinch, but that would be just
one more thing going on inside your mind like everything else. It's no use: If you want to find out whether what's inside your mind is any guide to what's outside your mind, you can't depend on how things seem - from inside your mind - to give you the answer.
Thomas Nagel