Cartesian Doubt


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  • Created by: Amy
  • Created on: 12-05-12 16:52


  • We could be wrong about what we 'know' 
  • discounted anything that could possibly be mistaken
  • 3 waves of doubt: failure of one's senses; we are dreaming; the whole world is a fiction generated by an evil genius
  • The Cogito - "Cogito ergo sum" - i think therefore i exist/am. This is all that he knows to be true
  • Apple Barrel - the first apple we pick out of the apple is good, as is the second. However, the third is rotten. We now know that the barrel could be tainted, and cannot be trusted. Whatever knowledge is like this, cannot be trusted
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Knowledge attained through our senses is easily confused and therefore cannot be relied upon. The only way to aquire knowledge is through contemplation and reasoning.

·         Descartes explained that a traditional candle (wax) was specific to the senses; it made a sound when struck, it looked solid and cylindrical, it felt smooth and waxy and gave a smoky smell when lit and otherwise smelt of honey.

However, when it melted, it changed completely. It made no sound, it was liquid and had no smell. Therefore, we cannot trust what we perceive to be true, as it can change. 

Due to Descartes’ analogy of the wax, we cannot perceive things with our senses as they are, as they can change and our perceptions of them are different. Also, our ideas of things are subjective and could change from person to person

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Backs wax theory up with his theory – he looks outside the window on a winter’s day and sees people in hats and coats. He knows that there are people wearing them, as he knows hats and coats do not walk around on their own. You can’t know specific facts about the world but you can understand concepts. You need the a priori knowledge of maths, logic and language to get you started

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  • Dreams can be distinguished from waking life – very different. 
  • Dreams come from waking life. A copy, or a response to waking life. (hume's complex ideas???) If dreams weren’t distinguishable from waking life, you wouldn’t know that you’d had them. 
  • In dreams, we have no control. In this world, we do have control.
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even with mathematical truths we can make mistakes – could someone or something be causing us to make mistakes about our perception of the world?

Hypnotists can make as perceive objects that do not exist. Could there be an ‘all deceiving demon/hypnotist’ at work?

“if we cannot tell the difference between the real world and a perfectly created false world, does it matter we’re being deceived?”

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