the limits of knowledge Flashcards
am i a brain in a vat
- if I know that P, then I know that I am not a brain in a vat (if A then B)
- I do not know that I am not a brain in a vat (not B)
- thus, I do not know that P (therefore no A)
- where P is any proposition
Putnam’s response
- our words do not refer to something unless there is an ‘appropriate causal connection’
- eg if an ant traced out the name Winston Churchill in the sand it would not be referring to Winston Churchill
- when a brain in a vat thinks ‘tree’ that word is not casually connected to trees, but to electrical circuits in a computer
- so, when the brain thinks about trees, its belief can be true because the word ‘tree’ refers to something different for the brain in the vat than for us
normal incredulity
- ordinary doubt or everyday scepticism
- doubting whether some claim is true
- it is usually in response to particular reasons or evidence
- eg having doubts about what the capital of Canada is
philosophical scepticism
- not in response to particular circumstances
- often a doubt about a whole way of knowing
local scepticism
- scepticism about a particular claim or area of knowledge
- eg scepticism about ethical knowledge
global scepticism
- scepticism about all knowledge
- eg brain in a vat, Descartes’ evil demon, simulation thesis
the purpose of philosophical scepticism
- philosophical sceptical scenarios are usually not proposed as serious theories to be accepted
- they are a challenge to our theories of knowledge
- they challenge us to consider whether our ways of knowing or theories of knowledge can refute them
- they challenge us to explain how knowledge is possible given that sceptical scenarios are a possibility
Descartes’ response to scepticism
- the cogito: I think therefore I am
- I know the cogito because it is clear and distinct therefore all clear and distinct ideas are true
- I can use this to prove that God exists and God is no deceiver
objections to Descartes
- even if ‘I’ exists, how do I know what the ‘I’ is, or whether it exists through time
- cartesian circle: Descartes uses clear and distinct ideas to prove that God exists, the argues that he can trust his clear and distinct ideas because God is no deceiver
empiricist responses
empiricists limit knowledge to the following:
1. a priori knowledge of analytic propositions
2. a posteriori knowledge of synthetic propositions about the external world
3. knowledge of our own minds
- empiricists also reject high standards for knowledge such as infallibilism
- we should accept fallible knowledge
empiricists responses - Locke, Russell and Berkley
- John Locke and Bertrand Russell argue that the external world is the best explanation of our experiences
- eg Russell says when we see a cat in one place and then look back and see it in another, the best explanation is that there is a mind independent cat that exists when we are not looking
- in contrast, Berkley argues that there is no appearance/reality distinction
- appearance is a reality
objections to empiricism
to Locke and Russell
- this means the external world remains a hypothesis
- is the external world the best hypothesis
- brain in a vat explains it just as well
to Berkley
- creates new problems, eg hallucinations, solipsism
reliabilist responses
- reliabilism rejects the view that justification is required for knowledge
- knowledge is a true belief produced by a reliable method
- the embodied person and the brain in a vat person are both equally justified in their belief
- but the embodied person’s beliefs are produced by a reliable method and the brain in a vat person’s are produced by an unreliable method
- this means that you have knowledge as long as you are not in a sceptical scenario
objections to reliabilism
- how do i know that i am not a brain in a vat
- response: i don’t need to know, reliabilists claim that you can have knowledge without knowing that you know
- the new evil demon: reliabilism doesn’t explain what is good about the brain in a vat’s belief, the brain in a vat is being a responsible believer
- response: the brain’s beliefs appear good because the brain is doing what would normally be reliable
kk principle
- to know, you must know that you know
- reliabilists reject this
