Scepticism

Plato’s definition of knowledge

A justified, true belief

Local scepticism

Doubting one particular thing, concept or piece of knowledge

Global scepticism

Doubting everything at once

Questions our own bodies, the world around us, knowledge based on our experiences

Cartesian Doubt

Where Descartes systematically strips away any belief that can possibly be doubted to find an indubitable foundation for knowledge

Descartes 3 waves of doubt

We could be seeing things wrong (our senses)

We could be dreaming

An evil genius/demon could be controlling us (like a brain in a vat)

Descartes - how do we know we exist?

Cogito Ergo Sum- I think therefore I am.

If you are to doubt you are thinking, you are still thinking.

Descartes - why is certainty found in knowledge?

The idea must be clear and distinct

Clear

When we are able to think about an idea fully with all the attention of our mind- there is nothing missing that could make it false.

Distinct

the idea is clear and is not defined in terms of anything else- it is something in and of itself.

Descartes and God

God is clearly and distinctly a ‘supremely perfect being’

God is an ‘infinite being’

The Casual Adequacy Principle

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

Descartes Trademark Argument

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

My ideas must be caused by something.

I am an imperfect being.

I have an idea of God, which is a supremely perfect being.

Therefore, i cannot 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.

Can we rely on clear and distinct ideas?

God is a ‘supremely perfect being’.

One perfection is being all powerful.

if God is all powerful then an evil demon could only deceive me if God allowed it.

This would make God a deceiver.

God is not a deceiver because he is a supremely perfect being.

Therefore, God will not, nor permit an evil demon to deceive me.

What is the trademark we are all born with?

The innate idea of God.

Descartes Wax Argument

When you look at wax you always perceive something different - its qualities don’t remain the same.

However, we still know its wax even if its qualities have changed.

This shows that the ‘concept of wax’ is not understood from its qualities.

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

Know it’s wax - clearly and distinctly.

Descartes approach

Descartes is a rationalist

Empiricists responses to scepticism

Trotter-Cockburn, coherence of experience.

Locke, voluntary and involuntary

Russell, ‘best hypothesis’

Problem with empricism

They give no reason why globally, it is a better hypothesis that there are things in the world.

We have as much evidence that we are a brain in a vat as we have that we aren’t- nothing can prove to us either way.

Arguments may work for local scepticism but not for global.

Reliabilism

rather than defining knowledge as needing to be ‘justifiable’, it argues it must be ‘reliable’ meaning it is based on some reliable cognitive processes.

So, the senses, clear memories, testimony from other reliable people can all constitute a reliable process which means we can say we ‘know’ something.

Reliabilism explained

So according to reliabilism, I may be a brain in a vat and I don’t have a reliable process to demonstrate if that is true or false. But that does not mean I cannot say that ‘I know there is a tree over there’- this still makes sense as according to my senses, which generally show themselves to be reliable, there is.

What they might say is that we don’t know for sure that we know that a tree exists.

Much more flexible way of defining knowledge.

Does reliabilism work?

reliabilism doesn’t show that objects exist, only that perceptions of objects exist (based on reliable processes).

but the reliabilist could argue that this is misunderstanding their theory- i do know that physical objects exist, I just don’t know if i know it.

Think about animals, they know things they can eat through perception but they don’t know why they know it. does this mean the animals don’t know anything

another response to scepticism -acceptance

accepting radical scepticism - there really isn’t anything we know for certain. we have to accept that everything we ‘know’ could be false.

There are definitions of knowledge that accept this, but not for Descartes who wanted indubitable knowledge.

You can be a radical sceptic and argue against a definition of knowledge that requires certainty.

You can also claim that it is the best hypothesis considering we cannot know for sure.

Cartesian Circle

Clear and distinct ideas are true, C+D idea of God used to prove, God exists, God’s omnipotence and goodness and confirm C+D ideas are true.

How to disprove Descartes trademark argument

The causal adequacy principle- if we can prove this wrong then the idea of a perfect being does not have to come from a perfect being

-examples against causal argument principle

-causation needs to be experienced to be known

- causation cannot be applied beyond the physical world

I have an idea of God as a Perfect being- if we can prove this wrong then the basis for the whole argument, that fact that our idea of God as an infinite and perfect God falls apart.

-do not have the idea of a ‘infinite’ or ‘perfect’ being, only the ideas of a ‘not finite’ and ‘not imperfect’ being.

Against causal adequacy principle

Evolution

David Humes on Causation

 The only reason we know about cause and effect at all is from experience.

for example if you had never seen water freeze before in cold temperatures - you would not know what caused water to become 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 is God himself.

Humes: cannot apply physical rules to the metaphysical

At best, Hume might allow that based on experience, the CAP can be applied to physical things. However, metaphysical things are beyond the physical universe and therefore the same rules may not apply.

Therefore, even if the casual adequacy principle is true, we cannot apply to God=this crosses Hume’s fork.

Hume’s attack on God as ‘supremely perfect’

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.

Humes argues that we do not in fact have the idea of the ‘infinite’ but instead something that is ‘not finite’.

In this way, we are able to explain God as a complex idea made up of qualities that we have just adapted from experience of humans.

Descartes vs Hume

Descartes considered Hume’s response himself. Descartes argued that to have the concept of ‘not finite’ or ‘imperfect’ requires an idea of a ‘perfect’ to negate- we don’t know we are imperfect unless we have an idea of perfect which we are not!

Other have argued this is not true- we have degrees of perfection that we understand but we don’t need to have a clear idea of ‘perfect’ to understand that some things are better than others.

Hume on substance

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

Instead, we perceive one object, 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 itself, but instead inferring it through similarity in our experiences.