Limits of knowledge AQA (scepticism)

What is moral incredulity

doubt a fact such as 'Paris is the capital of France', ordinary doubt

What is philosophical scepticism

beyond ordinary doubt and casts uncertainty over everything we think we know (e.g. Descartes evil demon, the matrix, simulation hypothesis, brain in a vat)

Explain the brain in a vat argument

If all your experience is just electrical signals interpreted by your brain, then you wouldn't be able to tell the difference if you were a disembodied brain in a vat being fed these same electrical signals artificially

Give an example of the brain in a vat using the statement 'I am outside walking my dog'

you may think you are outside walking your dog, but actually you are a disembodied brain in a vat being fed electrical signals that make you think you are outside walking your dog, so your belief you are outside walking your dog would be false and you have no way of knowing

Give the global sceptic argument for 'Brain in a vat'

If you can't justify your belief that you're not a brain in a vat, then you can't justify your belief that "I'm outside walking my dog"

And if you can't justify your belief that "I'm outside walking my dog", then you can't know "I'm outside walking my dog"

You can't justify your belief that you're not a brain in a vat

So, you can't know "I'm outside walking my dog" (or any other ordinary knowledge claim, such as "I know I have hands")

Explain ordinary doubt and justification

If you are unsure about ordinary doubt, you can resolve it by referring to some justification. E.g. If I doubt that my friend's birthday is tomorrow, I can check my calendar and once I see that I have written their birthday there, I know my belief is true

Explain what a global scepticism scenario is

go beyond normal incredulity and cast doubt on all typical methods of justification. E.g. If all my experience is just an illusion created by an evil demon, then I can't trust my calendar, I can't even trust my visual perception

Explain Descartes evil demon scenario

Can be shown with any ordinary knowledge proposition: "I know that grass is green" - the evil demon was tricking you and the grass is actually orange. "I know that Paris is the capital of France" - the evil demon was tricking you and France doesn't exist

All the scenarios are possible and there is no way to know otherwise

Thus, the possibility of the evil demon undermines all our usual justifications and casts doubt over everything we ordinarily consider to be knowledge

The global sceptic thus believes that all knowledge is impossible

Describe Descartes cogito

'Cogito ergo sum' - 'I think, therefore I am'

Even if you were to doubt you are thinking then you're showing that you're still thinking and an evil demon can't deceive you of this as thinking is self-evident

Argues his indubitable truth: He is a 'thinking thing'

What argument did Descartes produce from his cogito

1. In this first item of knowledge (cogito) there is simply a clear and distinct perception of what I'm asserting 2. If clarity and distinctness don't guarantee truth, then I cannot know that I exist 3. I do know that I exist 4. Therefore, generally, whatever I perceive clearly and distinctly is true

What are clear and distinct ideas

He is arguing that certainty is found in knowledge such as his cogito for 2 reasons

Clear = when we can think about an idea fully with all the attention of our mind (therefore we can't be distracted by other information and there is nothing missing that could make it false)

Distinct = if the idea is clear and not defined in terms of anything else; it is something in and of itself (not defined in terms of anything that could be false in itself and then put the current idea in doubt)

What is Descartes definition of God

clearly and distinctly a 'supremely perfect being'

What is the causal adequacy principle

'There must be at least as much reality in the efficient and total cause as in its effect'

If something occurs, what caused it to occur must have the necessary force or power to produce it

What does Bernard Williams say on this?

If you saw a picture of a sophisticated machine, you would think it was something from the future. If you saw an actual working sophisticated machine it would be more impressive. He argues the greatness of an effect (something created) must be matched or surpassed by its cause

Trademark argument

The cause of anything must be at least equal to its effect (causal adequacy principle)

My ideas must be caused by something

I am an imperfect being

I have an idea of God who is a supremely perfect being

Therefore, I can't be the cause of my idea of God

Only a perfect being can be the cause of my idea of God

Therefore, God must exist

Wax example (argument for substance)

When you look at wax you always perceive something different (qualities different)

However, we still know it's wax even if all its qualities have changed

This shows the concept of wax isn't understood from its qualities

In fact, I know that wax can change into all sorts of forms - more than I can imagine

Therefore, whatever wax is, as a substance, I know in my mind alone, not from my perceptions of the object

Descartes argument for substance

When I melt a piece of wax, it loses all its original sensory qualities

Despite this, I believe it is the same wax

Therefore, what I think of as wax, does not come from its sensory qualities

The concept of 'substance' I have is something extended (size, shape ect.) but something changeable (its sensory qualities: smell, colour ect.)

I know that wax can undergo more changes than I can imagine

Therefore, I know my concept of substance doesn't come from imagination

Therefore, my concept of wax is understood by my mind alone

Therefore, my concept of substance is clear and distinct

Argument for certainty of the external world

I have perceptual experiences as if of physical objects, which must have a cause

This cause must either be my own mind, God or external physical objects

If the cause were my own mind, these experiences would be voluntary (under my control)

However, they are not voluntary

If the cause were God, then those perceptual experiences would be deceptive (given that I have a strong tendency to believe physical objects exist)

However, they can't be deceptive as God exists and isn't a deceiver

Therefore, those experiences must be caused by external physical objects

Therefore, there is an external world of physical objects

What does Descartes say about the external world and rationalism?

argues our idea of 'substance' (i.e. the matter that things are made of) is a concept deduced using rationality, not perceptions. So, our concept of physical substance can't be doubted in the same way the properties it has can be - properties are subject to deception, but substance is not. Argues for a form of indirect realism

Hume on self (response to cogito)

Hume says a thought implies one thought

He says we don't experience a continuous self but rather a series of conscious thoughts one after another, constantly changing

There is similarity in these thoughts as we connect them up as we notice similarity and therefore infer there is a single mind thinking this series of thoughts

Hume points out we never experience a single mind, we reflect upon each thought but not on all at once

Hume on substance (response to substance argument)

As with the mind, he argues we never perceive one, continuous object

Instead, we perceive one object, then another, then another ect. Each time we look in a similar direction

The idea of continual substance then comes from seeing similarity between these perceptions and assuming there is a continuous, existing substance or physical object (even though we never directly experience it)

So, like the mind, we find the concept of substance not through experience, but through similarity in our experiences

Attack on clear and distinct ideas

Descartes accused of using circular logic as C and D ideas are only certain if God exists but for God to exist, we must know that C and D ideas are certain. Each point relies on the other to be true, there is no foundation for the other to be true

Attack on causal adequacy principle

There are times when it is possible to create something with more reality or perfection than its cause

Example = using a match to start a large fire, clapping to produce an avalanche, evolution

Hume on causation (response to causal adequacy principle)

The only reason we know about cause and effect at all is from experience (for example, if you have never seen water freeze in cold temperatures you wouldn't know what caused ice)

The only way to know about the cause of anything is by observing it in conjunction with its effect, as we have never experienced the cause of our idea of God, we cannot say it's God himself

We can't apply physical rules to the metaphysical (crosses Hume's fork)

Attack on God as 'supremely perfect' (Hume)

God is just a being with all the attributes of a human, but 'extending beyond all limits', we get these ideas from experiencing them in humans, then augment them in our imagination

Hume argues we don't in fact have the idea of 'infinite' but instead something that isn't 'finite'

So, we can explain God as a complex idea made up of qualities that we have adapted from experience of humans

Descartes response to Hume's attack on God

Descartes argued that to have the concept of 'not finite' or 'imperfect' requires an idea of 'perfect' to negate - we don't know we are imperfect unless we have an idea of perfect, which we aren't

Response to this

Others have argued this isn't true; we have degrees of perfection we understand but we don't need to have a clear idea of 'perfect' to understand that some things are better than others

Attack this: 'The cause of anything must be at least equal to its effect (causal adequacy principle)'

examples against the principle, causation needs to be experienced to be known, causation can't be applied beyond the physical world

Attack this: 'I have an idea of God who is a supremely perfect being'

don't have the idea of an 'infinite' or 'perfect' being, only ideas of 'not finite' and 'not imperfect' being

Russel's response to scepticism

Existence of the external world is the best hypothesis

P1. Either physical objects exist and cause my sense-data or physical objects do not exist and do not cause my sense-data, P2. I can't prove either claim is true or false, C1. Therefore, I must treat them as hypotheses, P3. The hypothesis that physical objects exist and cause my sense data is better, C2. Therefore, physical objects exist and cause my sense-data

Response to Russel

Descartes was never trying to prove that the evil demon doesn't exist, he was saying it was possible (a viable hypothesis)

Critique on that response

the possibility of the evil demon doesn't mean knowledge is impossible, Descartes is assuming an infallibilist definition of knowledge - he's assuming that we must know we're not being deceived by an evil demon to have knowledge. Russel could say certainty is not necessary, if we're not being deceived and our beliefs are true then our ordinary (uncertain) justifications are sufficient for knowledge

Possible other response to best hypothesis

Is the external world the best hypothesis? If we are being deceived by the evil demon, then our experience would appear the same as the external world, we have no grounds to prefer one hypothesis to the other

Locke's response to scepticism

Perception is involuntary, so suggests that perception is caused by something external to the mind

My different perceptions are coherent, suggesting a common reality causing both

Response to involuntary perceptions

even though Locke succeeds in proving something external is causing his perceptions, he doesn't prove this perception is an accurate representation of the world, the external thing causing them would be the evil demon

Response to coherence of senses

just because they are coherent doesn't mean they are representative of reality, an evil demon could create coherent senses

Berkely's response to scepticism

Idealism rejects mind-independent objects, evil demon argument never gets going against idealism as idealism doesn't make a distinction between perceptions and reality ('to be is to be perceived')

Argues his perceptions must be caused by something outside of him (God), almost like a benevolent version of the evil demon, his perceptions are not deceptions but his reality

Response to idealism

For this response to succeed, idealism must be the correct theory of perception. But idealism faces various problems, such as illusions and hallucinations

Definition of reliablism

a true belief formed from a reliable cognitive process

Examples of reliable cognitive processes

The senses, clear memories and testimony from other reliable people all counts as reliable methods so we can say we 'know' something

Argument for reliablism

I may be a brain in a vat, and I don't have a reliable process to determine if that is true or false. But that doesn't mean I can't say 'I know there is a tree over there' - this still makes sense according to my senses which generally show themselves to be reliable

How would they phrase not knowing something?

We don't know for sure that we know that a tree exists

Possible response to reliablism

reliablism doesn't show that objects exist, only that perceptions of objects exist

Reliablist response to critique

reliablist claims this is misunderstanding their theory - I do know that physical objects exist, I just don't know if I know it