1. The Limits of Knowledge
Understand what is meant by “philosophical scepticism”
Understand the role of scepticism in epistemology
Begin to evaluate Descartes’ use of scepticism

2. Philosophical scepticism vs. normal incredulity
We often doubt people’s claims. If someone says “it’s going to snow this weekend”, we may doubt whether this is true. But this is not the same as philosophical scepticism. This is just normal incredulity (disbelief).
At what point does this person’s thinking move from normal incredulity to philosophical scepticism? What is the difference between them?
It’s going to snow this weekend – I don’t think it will.
It says so on the weather forecast – the forecast could be wrong.
The forecast is based on science – science could all be wrong.
Science is the basis of all our knowledge about the world – all our knowledge about the world might be wrong.

3. Philosophical scepticism vs. normal incredulity I
Normal incredulity is sensitive to evidence – this means that new evidence can make you change your mind about it.
Philosophical scepticism is not, because when presented with new evidence, the philosophical sceptic can just doubt the evidence.

4. Philosophical scepticism vs. normal incredulity II
Philosophical scepticism is also more extreme. In everyday life, we may doubt certain small issues, but the philosopher may doubt whether his own hands exist, whether other people are mindless zombies, or whether the sun will rise tomorrow.

5. Philosophical scepticism vs. normal incredulity III
Philosophical scepticism is theoretical, rather than practical. For the philosopher, doubt is a tool used for investigating what we can know, not as a practical guide for how to behave.
For example, the philosopher may doubt whether physical objects exist, but will continue to lean on her desk and drink her cup of tea.

6. Local/ global scepticism
Local scepticism raises doubts with one particular area of knowledge
Global scepticism raises doubts with all our knowledge
Can you think of any examples?

7. Scepticism in Epistemology
Scepticism is used to test our knowledge claims. If we know something, then it must be true (remember the tripartite definition).
If our knowledge claims are easily doubted, we have less justification for believing them to be true. If they withstand our efforts to doubt them, they are more likely to be true.

8. Problem with scepticism
How do I prove that one belief is true? – by appealing to another belief. How do I prove that belief 2 is true? – by appealing to belief 3…
Problem – infinite regress
Why is this a problem??

9. Response to infinite regress
Foundationalism – find foundational beliefs that we trust, and base the rest of our beliefs on them.
Examples of foundationalist approaches are rationalism (based on the belief that rational deduction and intuition can provide us with a starting point for knowledge) and empiricism (based on the belief that sense experience can be relied upon as a basis for knowledge).

10. Reading Task Descartes’ first meditation
Read it slowly.
Use a sharp pencil to identify key points or bits that aren’t clear.
Use the margin to ask questions, and to summarise each paragraph/point.

11. Descartes’ scepticism

12. Descartes’ scepticism

13. Descartes’ scepticism

14. Descartes’ scepticism

15. Descartes’ scepticism

16. Descartes’ scepticism
How can we evaluate Descartes’ sceptical approach?

17. The Limits of Knowledge
Understand what is meant by “philosophical scepticism”
Understand the role of scepticism in epistemology
Begin to evaluate Descartes’ use of scepticism