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Shirly asked:
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What is Descartes's thesis regarding senses?
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As a philosopher, Descartes sought a true foundation for empirical knowledge which is knowledge of
the world received through sense experience. As a philosopher, he suggested that it is unwise to trust
the senses, since if they have deceived us once, they may do so again. However, as an ordinary
man, he thought that it is madness to doubt one's senses and as a philosopher he recognised that
although you can sometimes be wrong about sense experience it doesn't follow that you always are.
So the real problem of scepticism about knowledge of the external world is posed when Descartes
considers that he has dreamt in the past that he has been sitting by the fire with a paper in his hand
and he finds that "there are no certain indications by which we may clearly distinguish wakefulness
from sleep". So it is not that we can doubt our senses generally because they have deceived us once,
but that in any particular case we do not know whether or not we are dreaming. There is nothing
essentially qualitative in our experience that we can point to as proof that we are not dreaming. For
this reason, in any particular case we do not know whether we possess empirical knowledge.
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The general problem of scepticism, ie whether or not empirical knowledge is possible or whether we
are always dreaming, is answered by Descartes' arguments for the proof of the existence of God. If
we are not constantly being deceived by an evil demon, and if Descartes' argument for a benevolent
God is accepted, we can be sure that there is an empirical world and that our senses do not in
general deceive us. The argument lends support to the ordinary man's confidence in his senses, and
the philosophical position that even if we doubt our senses once, this doesn't mean we should doubt
the senses in general. So although Descartes argues that we can generally be confident in our sense
experience because of a benevolent God, and it is madness in a particular case to doubt our sense
experience, he does not solve this particular sceptical problem about how we know we are awake.
We do normally know this and it is only a practical problem if we are insane, but it remains a
philosophical problem of how we are to account for it.
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Rachel Browne
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