Rationalism 2

Rationalism 2

1. Using a priori intuition and demonstration to establish claims of what exists

   • Hume claimed that all matters of fact (including claims about what exists) must be grounded on experience and use of inductive reasoning
     • Rationalists say - some claims about what exists can be grounded instead on a priori intuition and demonstration
       • Demonstration - deduction
       • a priori intuition - can 'see' the truth of a claim just by thinking about it
   • Descartes
     • can establish the existence of the mind, the physical world and God through a prioir reasoning
       • Cogito - the mind
         • 'i think therefore i am' - so because i think i know i exist. may not have a body though ( a priori reasoning)
       • The physical world and God
         • what causes experience? God, physical objects or an evil demon?
           • if God - would be deceiving us. If evil demon - god is as good as deceiving us.
             • But God is perfect and would not deceive - if god exists physical world exists
     • say were plugged into super computer from the matrix - sense experience not good for telling what exists
     • criticisms
       • Cannot know you exist, only know that you think - therefore are thinking
       • thinks mind can exist without body - just because can conceive of possibility does not show that it is possible
       • Hume claims only 2 types of knowledge - reason can only demonstrate analytic truths; no such thing as intuition
     • Wax example - extension in space and infinity idea

2. Certainty is confined to introspection and the tautological

   • Descartes said knowledge is what' is completely certain and indubitable'
     • certainty and justification are different, need argument to show that it is certain
   • what is certainty?
     • 1) could be subjective, psychological meaning e.g. i feel certain that..". feeling of conviction
     • 2) could be logical meaning e.g. truth of proposition can be certain because logically true proposition
     • 3) Something that cant be doubted
     • 1) too subjective 2) cannot doubt most because must be true, 3) relevant
   • Necessary and contingent
     • proposition contingent if it could be true or false
     • proposition necessary if MUST be true e.g. maths or analytic truths
   • tautology: saying something twice in different words e.g. analytic proposition. what is tautological is certin. analytic truths are necessary;certain
   • introspection: beliefs on ones mental states and processes - known to be certain and cant doubt
     • contingent e.g. cannot doubt i seem to be seeing a table - but still certain (certainty def. no. 3)
   • Descartes thought necessity and certainty confined to a priori propositions.
     • What about necessity of causal chain?
       • Hume said an illusion! Habituated experience
       • E.g. flame melting ice