Scepticism

Scepticism is the view

that our usual justifications

for claiming our beliefs amount to knowledge are inadequate,

so we do not in fact have knowledge. Scepticism can target knowledge from any source, including perception and reason.

And so it challenges both empiricism and rationalism.

is scepticism about some specific claim scepticismim, or more commonly, about some area/branch of supposed knowledge.

We might doubt whether we can know how many planets exist in the universe (without doubting astronomy in general).

Or more broadly, we might doubt whether there can be any knowledge about God’s existence and nature (without doubting, say, scientific knowledge)

Global scepticism is scepticism about all knowledge claims.

focused esp. on having no knowledge of an external world of physical objects.

The brain in a vat provides an example.

If we can’t know whether or not we are brains in vats,

and cannot even trust our reasoning, then it seems all our knowledge comes into question.

If we can secure knowledge of such a mind-independent world, we will have defeated global scepticism.

scepticism about some specific claim scepticism, or more commonly, about some area/branch of supposed knowledge.

eg. We might doubt whether we can know how many planets exist in the universe (without doubting astronomy in general).

whereas

Global scepticism is scepticism about all knowledge claims.

Focused esp. on having no knowledge of an external world of physical objects.

The brain in a vat provides an example.

If we can’t know whether or not we are brains in vats, and cannot even trust our reasoning, then it seems all our knowledge comes into question.

P.S starts with ‘how’ we know something

doesn’t have to be practical or reasonable

attack the justification for knowledge

whereas

R.I. (e.g everyday doubt) attack certainty

we still work with practical use and questions whether something is completely true or not

1. the argument from illusion

2. the argument from dreaming

3. the argument from the evil demon

Descartes first wave of doubt begins by presenting an argument from illusion as any of his beliefs are based on his sense experience

In the past, been deceived by his senses – things have looked a way that they are not.

Things distant look small

pencil in water looks crooked.

BUT

Descartes remarks, such examples from unusual perceptual conditions give us no reason to doubt all perceptions

• special cases (and ones we can frequently explain).

• Otherwise wouldn’t be illusions.

• don’t undermine perception generally

Descartes second wave of doubt is that he could be dreaming and in this way he doubts the existence of his body and the world around him.

There is no reliable way to tell whether I’m awake or asleep.

arg. attacks all sense perception.

I cannot know that I see a piece of paper because I cannot know that I am not dreaming of seeing a piece of paper.

It questions whether we can tell what reality is like from what we experience, since those experiences could be no

We can object that there are reliable ways of distinguishing waking perception from dreaming, such as the far greater coherence of perception.

there are reliable ways of distinguishing waking perception from dreaming, such as the far greater coherence of perception.

The objection assumes that I can rely on my memory of what I have experienced to compare it with my dream.

the truths of geometry seem secure,

as to truths of arithmetic, such as ‘2 + 3 = 5’.

dreams are constructed out of basic ideas

must correspond to something real –

ideas of body, extension, shape, quantity, size, motion and time.

And so Even if he is dreaming, this seems impossible to doubt.

all experiences are produced evil demon who wants to deceive me.

If this were true, I wouldn’t know, because my experiences would be exactly the same (just as with the brain in the vat thought experiment).

I cannot know I am not being deceived by an E.D.

Descartes uses the E.D. ensure that he doesn’t believe anything he can’t know.

It seems that he can’t know anything - global scepticism.

John Locke responds to the problem of scepticism by claiming–

1) We are passive in perception which means we are not the source of our perception, something outside of us is.

• This is the same point Descartes made above and has the same problem. Also, all this shows is that we are not the source of our perceptions, it doesn’t show that our perceptions accurately reflect the world, i.e. it’s compatible with an evil demon or matrix style scenario.

2) If all our senses are in agreement we can be sure

• what we are perceiving is real –If you’re not sure whether a fire you’re seeing is real or not put your hand in it, if your hand burns the fire is real, if it doesn’t the fire is not real.

2. This response doesn’t work either because it’s simply not true, we often have experiences of things where all our senses agree and yet they are not real, e.g. dreams or hallucinations. Also, again, this is compatible with an evil demon or matrix style scenario (the senses of people in the matrix are all in agreement yet none of what they experience is real)

Russels best hyposhesis responds to the problem of scepticism by - Russell uses an inference to the best explanation type of argument.

Like Descartes earlier he asks ‘where do our perceptions come from?’ There are competing hypotheses:

1)There is no external world –our perceptions come from an evil demon or just from nowhere

2)There is an external world but it’s very different from what we experience (e.g. a matrix style scenario)

3)There is an external world and it’s just like what we experience He says the third of these is ‘the best hypothesis’. As we’ve seen, perceptions only last as long as they’re perceived (if you close your eyes or turn around your perception of whatever you were seeing is gone)

. If there were no external world and just perceptions then when you’re not looking at or seeing something it doesn’t exist. So how come the things we experience behave as if they DO exist as more than just perceptions? How come if I light a candle in a room and leave it on its own for a few hours when I return the candle has burned down? How come if I leave an apple in a drawer for a few weeks when I come back it has gone rotten?

argues we have 3 types of knowledge

• a priori knowledge

• a posteriori knowledge

• knowldege of our own minds based on sensation and reflection

this means that we might still be sceptical of some things that aren’t part of tese kinds of knowldge, such as God or of morality

however we still shoukd blieve in phyicla objects as they are the best hypothesis

isue:

the sceptic might suggests that the external world i still just a hypothesis

we cannot know with certainty that physical objects exists

counter:

sceptic might be setting the standard for knowledge too high

empiricist might simply reject demand for certainty

If the bar for JTB has been ‘set too high’, we might object that the sceptic is simply searching for infalliablism

If the sceptical argument contends that sense-data tells us nothing about the reality of an object, Russel had a ‘common' sense’ response to this:

while we understand sceptical arguments, there is no reason to believe them.

A hundred different viewers have a thousand different kinds of sense data for a given table YET each agrees that they are looking at the same table #

consistency = existence of a single, articular, real table - “instinctive” belief,

R adds - ‘physical objects cause the sense-data we receive’ and

T, correspond to them in some significant way.

physical objects might not be the best explanation for our experience

• If i were a brain a vat, that would also explain my experiences equally well as physical objects

Perhaps experience only shows that something is external to our mind, but it doesn’t show us what

This arg. doesn’t go much further, it continues to appeal to inlliablism