Keyboard Shortcuts?

×
  • →Next step
  • ←Previous step
  • ↓Skip this slide
  • ↑Previous slide
  • mShow slide thumbnails
  • nShow notes
  • hShow handout latex source
  • NShow talk notes latex source

Click here and press the right key for the next slide (or swipe left)

also ...

Press the left key to go backwards (or swipe right)

Press n to toggle whether notes are shown (or add '?notes' to the url before the #)

Press m or double tap to slide thumbnails (menu)

Press ? at any time to show the keyboard shortcuts

 

Cosmic Doubt

‘How do I know that he has not brought it about that there is no earth, no sky, no extended thing, no shape, no size, no place, while at the same time ensuring that all these things appear to me to exist just as they do now?’

Meditation 1

Terminology:
you are cosmically deceived exactly if he has done this.

\subsection{Cosmic deception} ‘How do I know that he has not brought it about that there is no earth, no sky, no extended thing, no shape, no size, no place, while at the same time ensuring that all these things appear to me to exist just as they do now? What is more, since I sometimes believe that others go astray in cases where they think they have the most perfect knowledge, may I not similarly go wrong every time I add two and three or count the sides of a square, or in some even simpler matter, if that is imaginable?’
Is this a reason to doubt all things?

Sensory perception plus knowledge of platitudes alone do not enable you to know that
this planet is round, not flat.your birthplace has not been struck by a meteor.the world outside this room continues to exist.you aren’t cosmically deceived.

The senses are concerned with the appearances of things here and now.

You do know this platitude:
if you are drinking coffee, then you are not cosmically deceived

Suppose sensory perception alone enables you to know you are drinking coffee.

Then you would be in a position to know you are not cosmically deceived on the basis of sensory perception plus knowledge of platitudes only.

Therefore sensory perception alone does not enable you to know you are drinking coffee.

Look where we got from and to!
Note the limits of the argument. It is not a general scepitcal argument.
Are the premises of this argument true? Is it valid?

Meditations (Synopsis)

Reasons are provided ‘which give us possible grounds for doubt about all things, especially material things,
so long as we have no foundation for the sciences other than those we have had up until now’

Earlier I asked, what are those reasons? Now we know.
Note the qualification!

✓

Earlier I asked, How can the mere possibility that cosmic deception might occur give us grounds for doubt? Now we know.

How can the mere possibility cosmic deception might occur give us grounds for doubt?

This question is answered by the argument. The argument shows that we lack of knowledge of mundane things on the basis of sensory perception and knowledge of platitudes alone.

so long as we have no foundation for the sciences other than those we have had up until now

These are the questions I’ve been thinking about. I’ve given you my answers. You can find other answers by reading Descartes and the secondary literature. What will your answers be?

Questions

1. Is Descartes’ appeal to cosmic deception supposed to provide reasons which give us possible grounds for doubt about all things?

2. If so, how is Descartes’ appeal to cosmic deception supposed to provide reasons which give us possible grounds for doubt about all things?

3. Does it succeed?

\begin{enumerate} \item Is Descartes’ appeal to cosmic deception supposed to provide reasons which give us possible grounds for doubt about all things ? \item If so, how is Descartes’ appeal to cosmic deception supposed to provide reasons which give us possible grounds for doubt about all things? \item Does it succeed? \end{enumerate}
Steve’s attempt to answer question 2: \begin{enumerate} \item Sensory perception plus knowledge of platitudes alone do not enable you to know that you aren’t cosmically deceived. \item You do know this platitude: if you are drinking coffee, then you are not cosmically deceived \item Suppose (for a contradiction) that sensory perception alone enables you to know you are drinking coffee. \item Then you would be in a position to know you are not cosmically deceived on the basis of sensory perception plus knowledge of platitudes only. \item Therefore sensory perception alonedoes not enable you to know you are drinking coffee. \end{enumerate}

Argument ideas from Meditation 1

The senses sometimes deceive us

My brain may be ‘damaged by the persistent vapours of melancholia’

The dream argument

The deceiving God hypothesis

Cosmic deception

We’ve been considering just one argument idea.
Lots of arguments. Can ask the same three questions about each.