Limits of Knowledge and Scepticism AQA A-Level Philosophy

What is normal incredulity?

• commonplace everyday questions about human life

• the kinds of practical considerations that happen to matter in that context

• secondary derivative concern which is dependent on knowing that I have a body and veridical experiences

What is philosophical scepticism?

• Philosophical scepticism is not so concerned with practical knowledge but more about abstract knowledge

  • Descartes’ evil demon

  • The Matrix

  • The simulation hypothesis

  • Perfect virtual reality

  • Brain in a vat

• less concerned with discovering if we can judge things that affect practical life

• more concerned with whether we can hold any knowledge at all regardless of its significance for human life

• casts doubt on pretty much everything we ordinarily consider to be knowledge

What is the the role/function of philosophical scepticism within epistemology?

• most view it as a challenge or difficulty to be overcome

• to determine what, if anything, we can know

• the sceptic typically questions the adequacy of the justification for supposed knowledge

  • if the justification is that we can perceive what we claim to know, the sceptic would point out that we might be a brain in a vat with no veridical perceptions and so that justification fails

What is local scepticism?

* scepticism about:
* particular claims (e.g. a particular sense experience)
* domain of claims (e.g. all sense experience)
* Local scepticism occurs when our reasons for doubting are the sort which apply to specific knowledge claims.

What is global scepticism?

Global scepticism results from the reasons for doubt apply not to specific knowledge claims but seem to undermine all possible knowledge claims:

* e.g. the brain in the vat where scientists could manipulate our reasoning about mathematical concepts and our perceptual experiences both of the external world and our own mind.

What is Nick Bostrom’s simulation argument (contemporary global scepticism argument)?

P1: Minds can be simulated on computers.

P2: Once a civilisation gains the technology to do so, it will simulate minds on computers which have conscious experiences indistinguishable from our own.

P3: This will occur multiple times such that the number of simulated worlds will vastly outnumber the number of real worlds (one).

C1: we should expect as a matter of probability to be in one of the simulated worlds.

What strength of the simulation argument over the dreaming argument or the brain in the vat hypothesis?

it’s not simply a very difficult possibility to rule out but is actually overwhelmingly probable

What are Descartes’ sceptical arguments (three waves of doubt)?

• Argument from illusion

• Argument from dreaming

• Deception (demon controlling your mind)

What is the first wave of doubt?

**The 1st wave of doubt** is the argument from illusion

* Descartes doubts his perception since it has gone wrong in the past
* e.g sticks in water look bent

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however, Descartes does not think this subjects all perceptions to doubt, only those special cases

What is the second wave of doubt?

**The 2nd wave of doubt** is the argument from dreaming

* casts doubt on all my current perceptions by claiming that I could be dreaming
* in that case my perceptions might not be of reality
* therefore they cannot provide certain knowledge

What is the third wave of doubt?

• The 3rd wave of doubt casts doubt on knowledge of mathematical and logical truths, which Descartes claims withstands the dreaming argument

• Another example of global or philosophical scepticism

Descartes postulates that instead of a God there could be an evil demon deceiving you about supposed mathematical truths, so even they cannot be certain knowledge

What is a modernised example of the demon controlling your brain argument?

The brain in a vat scenario:

• supposes that your brain is not in your body but is being manipulated by scientists to generate your conscious experiences

• if that were the case you would never know

• this is similar to the evil demon argument but more conceptually analysable and can therefore be more easily said to be a logical possibility

• seems to have the same outcome as Descartes’ third wave of doubt, as the scientists could manipulate our brains to think that 1+1=3 when really it is 5

These are situations where everything you believe could be false and there would be no way of knowing.

What is Descartes own response to the demon argument?

• Cogito shows that if we’re being deceived by the demon, we can at least be certain that we exist

• God exists and is a perfect being

• God would not allow us to be globally deceived

• We can therefore trust our own perceptions because the external world exists

• If we can trust our perceptions then they can justify the knowledge of ordinary propositions- eg, I exist

• This therefore defeats global scepticism

What is the evil demon argument?

• Third wave of doubt, the arguments of deception, global/philosophical scepticism

• Ordinary doubt requires justification

• Global scepticism goes beyond normal incredulity, and casts doubt upon typical methods of justification, ie. Vision

• You cant be sure anything exists because you can't trust your perception

• Eg, grass may not be green, 2+2≠4 because the demon may be tricking you, and the external world is an illusion created by them

• Therefore, all knowledge may be impossible since our perception may not be veridical

What is Locke’s first empiricist response to scepticism?

• Perception is involuntary, like our imagination

  • suggests something external causes our perceptions

  • he is unable to avoid having certain sense data produced in his mind when he looks at an object

  • memory and imagination allows him to choose what he experiences

  • One’s differing perceptions are coherent (e.g.. sight and sound)

  • suggests a common reality causing both

What is Locke’s second empiricist response to scepticism?

• One’s differing perceptions are coherent (e.g.. sight and sound)

  • suggests a common reality causing both

  • different senses confirm the information of one another

    • you can write something on a piece of paper and see the words

    • You can get someone to read the words out loud and thus hear the same information via a different source

    • our experience in one sense allows us to predict what we experience in another sense

  • The external world explains why our perceptions are:

    •  involuntary

    • cohering

    • allowing the prediction of experince in other senses

What is Russell’s empiricist response to scepticism?

Russell’s response to the IDR sceptical challenge that says the existence of the external world is the best hypothesis.

• Either:

  • A: the external world exists and causes my perceptions

  • B: an evil demon exists and causes my perceptions

•  I can’t prove A or B definitively

•  So, I have to treat A and B as hypotheses

•  A is a better explanation of my experience than B

•  So, mind independent objects exist and cause my perceptions

What is the first sceptical objection to Locke’s empirical argument?

Initial sceptical response:

• Locke succeeds in proving something external is causing his perceptions

• doesn’t succeed in proving that this perception is accurate representation of the external world

  • the external something, could be the demon

What is the second sceptical objection to Locke’s empirical argument?

Sceptical response to Locke’s point about the coherence:

• our different senses are coherent

• may not be representative of reality

• evil demon could create coherent experiences

• could deceive you into hearing dogs barking at the same time as seeing dogs

  • would be subjectively indistinguishable

  • Demon could just be creating coherent sound and visual perceptions

What is a possible response to Russell’s empiricist response to scepticism?

Russell could respond back that the possibility of the evil demon hypothesis does not mean knowledge is impossible

Descartes is assuming an infallibilist definition of knowledge, but certainty is not necessary

as long as we’re not being deceived and our beliefs are true then our ordinary (uncertain) justifications are sufficient for knowledge

What is the reliabilist response to scepticism?

Reliabilist definition of knowledge:

• true belief formed via a reliable method.

• my perception would count as a reliable method of gaining knowledge

• my perceptions reliably cause me to form true beliefs

Although you cannot prove whether or not the demon exists, it does not matter because, you don’t have to know my perception is reliable in order for it to count as a reliable method

• reliability is a fact independent of their knowledge

What is the first scenario posed by the reliabilist response to scepticism?

• Scenario 1: I am not a brain in a vat

  • My perception is a reliable method because I’m living in the real world and am perceiving it accurately

  • My perception leads me to the belief “I have hands”

  • My belief is true, because this is scenario 1 and I’m not a brain in a vat

  • So I have a true belief formed via a reliable method that “I have hands”

  • So, according to reliabilism, I know “I have hands” in scenario 1

    • (so, if you’re not actually a brain in a vat, you can know “I have hands”)

What is the second scenario posed by the reliabilist response to scepticism?

• Scenario 2: I am a brain in a vat

  • My perception is not a reliable method because I’m a brain in a vat being fed artificial stimuli

  • My perception leads me to the belief “I have hands”

  • But my belief is false, because this is scenario 2 and I’m actually a brain in a vat

  • So I have a false belief formed via an unreliable method that “I have hands”

  • So, according to reliabilism, I do not know “I have hands” in scenario 2

    • (which would be correct – you don’t want a definition of knowledge that says you know you have hands when you don’t have hands)

What is Descartes’ project?

In order to have a secure foundation for knowledge, science, like mathematics needs some/a foundational propositions upon which all other knowledge can be built 

In order to ensure that foundation is secure there must be no possibility of doubt 

Rather than go through his beliefs one by one Descartes will examine if there are any grounds to doubt the senses which are the source of all our beliefs 

Therefore, we should treat all beliefs that could be wrong as though they have been proven to be false 

What are the three empiricist responses to scepticism?

• Russell

  • External world best hypothesis example

• Berkeley

  • Idealism

• Locke

  • IDR responses that perception is

    • involuntary

    • coherent

What is Berkeley’s empiricist response to scepticism?

• Idealism rejects mind-independent objects

• Sceptical scenarios where mind-independent objects:

  • don’t exist

  • radically different from our perceptions, aren’t really possible

• idealism doesn’t make a distinction between perceptions and reality

  • the immediate objects of perception are mind-dependent ideas

  • no external world independent of minds

• his perceptions must be caused by something outside of him

• Therefore must be the mind of God

  • benevolent version of the demon

  • causing his perceptions, rather than being a deception

  • said perceptions are just reality

We can’t know whether we’re in scenario 1 or 2, so we can’t know that we know such propositions – but we don’t have to.

What is the conclusion of the reliabilist objection to scepticism?

You can know something without knowing that you know that thing.

Knowledge is possible if ‘knowledge’ is defined as true belief formed via a reliable method, assuming we are not in a sceptical scenario

If I am not a brain in a vat, then my perception is as a reliable method and so I can know ordinary propositions such as “I have hands”

What is the possible response to the reliabilist objection?

• Sceptics can argue that the reliabilist definition of knowledge is untrue

  • fake barn county

    • Henry’s true belief that “there’s a barn” is caused by a reliable cognitive process – his visual perception

    • Reliabilism would thus (incorrectly) say that Henry knows “there’s a barn” even though his belief is only true as a result of luck

• we can’t provide proper justification for ordinary knowledge as we can’t justify that we’re not in a sceptical scenario if we use another definition of knowledge

• if any of the other definitions of knowledge are correct, I cannot know “I have hands”

• you must first defeat the sceptical challenge and we’re back to square 1