as above

1. Descartes: Infallibilism
His arguments in Meditation One

2. Goldman’s view of Cartesianism
• ‘The Cartesian view combines a theory of knowledge with a
theory of justification. Its theory of knowledge asserts that S
knows that p at t only if either a) p is self-warranting for S at t
or b) p is strongly confirmed by propositions each of which is
self-warranting for S at t.’
• ‘These must be propositions about S’s mental state and
perhaps some obvious necessary truths.’
• ‘A major task…is to show that there is some such set of self-
warranting propositions that support external-world
propositions.’

3. Infallibilism outlined
• another way of rescuing the JTB account
• strengthens the Justification condition to include
notion that justification must be infallible (=‘can’t be
wrong’)
– as only certainty is sufficient justification for a knowledge-
claim to succeed
– knowledge itself is certain / cannot be mistaken
• Goldman: Infallibilism is the ‘traditional Cartesian
perspective in epistemology’
• a.k.a. knowledge must have infallible foundations.

4. Strengths of Infallibilism
• infallibilists can dismiss Gettier counterexamples
because
– They are not infallibly justified
– So are not examples of justified true belief
– So are not examples of lucky but successful JTB
knowledge-claims
– So are not counterclaims against the tripartite definition.
– If anything, they show only that our beliefs are rarely well-
enough justified to count as knowledge.

5. But! Issues with infallibilism…

6. Infallibilism in Standard Form
1. You cannot know what is false
2. So if you know that P, you cannot be mistaken about P.
3. So for knowledge-claims to succeed, justification must
be infallible.
4. Therefore if I am justified in believing that P, I cannot be
mistaken that P.
5. So if it is possible I am mistaken that P, then I cannot
be justified in believing that P.
6. So infallibilism is true.
So infallibilism rules out Gettier counter-examples, because
in these cases you do not have justified true belief.

7. Infallibilism in Standard Form
1. You cannot know what is false
2. So if you know that P, you cannot be mistaken about
P.
3. So for knowledge-claims to succeed, justification must
be infallible.
4. There are infallible justifications.
5. Therefore if I am justified in believing that P, I cannot be
mistaken that P, (and if it is possible I am mistaken that P, then I
cannot be justified in believing that P).
6. So infallibilism is true.
So infallibilism rules out Gettier counter-examples, because
in these cases you do not have justified true belief.

8. Rene Descartes, infallibilist
• An example of someone who
thought that knowledge had
to be infallibly justified
• 1596-1650
• irritatingly polymathic:
mathematician, scientist,
philosopher, soldier etc
• Lazy: “I have my best ideas
in bed…”
• Known for (vaguely religious-
sounding) ‘Meditations on
First Philosophy’

9. Descartes: not a sceptic
• For Descartes, knowledge = 100% certain
• Because:
– in his time, C17 belief system has weak foundations
– weak foundations = the whole structure collapses
– so all knowledge-claims in his time are dubitable
• Descartes is a rationalist foundationalist
– Rationalist: basing knowledge on pure reason, not
sense experience
– Foundationalist: knowledge must rest on a
foundation of infallible beliefs.

10. Descartes’ Decision
• To demolish and start over:
– Descartes will not doubt each individual belief, as this
is a bare long mission.
– Rather he will generalise his doubt, and if he can find
doubt in one instance, he will doubt everything in this
category.
– He is not saying that all his beliefs are false, just that
he will WITHHOLD ASSENT from them, meaning that
he will not trust them as truth
• The Barrel of Apples metaphor.
– First barrel of apples: the senses and sensory
experience
– …so, all ideas derived from sensory experience.

11. Descartes’ Method
• Known as ‘Cartesian Method’ or ‘methodological
scepticism’
• Amounts to:
– Using the tool of systematic doubt to dismiss whole
classes of ideas…
– to arrive at certain foundation for knowledge-claims
– …so uses the sceptic’s own sceptical method, like a
judo expert using opponent’s body weight to win.

12. Descartes’ Conclusion
• The view that claims to know about what exists
or occurs can be ultimately justified by sense
experience has serious problems.
– (We will look at the defenders of empiricist
foundationalism later on…)
• In contrast, the view that some fundamental
claims about what exists can be grounded in
and justified by a priori intuition and/or rational
demonstration is highly plausible.
– Descartes is a rationalist foundationalist,
remember?

13. How does Descartes reach his
conclusion?
• By offering us three sequential
steps or waves of argument
• the ‘Three Waves of Doubt’
• Which undermine our certainty
that our senses are to be relied
on as a source of justification

14. Wave 1: The Argument from
Error (or Illusion)
• My senses sometimes deceive me.
• Anything that sometimes deceives me
cannot be trusted at all
• So I cannot trust my senses.
– The Towers example

15. Responses to the Argument from
Error
• But not to trust my senses is crazy, unliveable.
• And I can check again or cross-check with other senses
to see e.g. if my crisps do taste of cheese and onion
• And – the Benchmark or Forgery problem
– the only way I know my senses are deceiving me is through my
senses…
– so I have to trust my senses to show me that my senses are
wrong…which might be contradictory
• And perhaps I am not entitled to generalise on the basis
of only a few examples of sensory error
– Is Descartes’ 100% rule for certainty correct?
• And (Descartes admits this) when I have sensory
experience, I am conscious of something, after all.

16. Wave 2: The Argument from
Dreaming
• What if, says Descartes, consciousness
itself is suspect?
– I have sometimes been unsure whether I was
asleep or awake, because of vivid dreams.
– And if I have even once been unsure, then I
cannot be sure that I am not dreaming now.
– So my senses are not to be trusted at all.

17. Responses to the Argument from
Dreaming
• Appeal to consistency – dream-logic is odd and we can
usually tell in the end
– Thomas Hobbes – there are ‘conclusive signs’ that one is
dreaming…
– Does this reply work? (‘Even once…’)
• Appeal to content – dream content isn’t derived internally
– For dreams to be possible, there are preconditions: dreams
remake content that we have received from the outside world.
– the idea of ‘Simples’ – basic ideas which we use to make up
more complicated ones – means that imaginary things still have
real shapes and colours.
– So we must have been awake at least once, to absorb this
simple content.
• But what if Descartes were to point out that we could still technically
be dreaming at this moment?

18. And: is dreaming radical enough?
• Even in a dream, mathematics still applies.
– Two purple flying mice + two green flying mice will
still= four flying mice.
– The dreaming argument is not enough to allow him to
doubt maths, geometry and logic.
– These still apply even in dreams, surely?
• Appeal to a priori concepts shows that these are
still certain…
– Could anything loosen Descartes’ hold on a priori
knowledge?
– …or might a priori knowledge be infallibly justified?

19. Wave 3: The Evil Demon
Argument
• …what if an infinitely powerful being deliberately
misleads you about your sensory experience?
– Descartes calls this being ‘an Evil Demon’ – why?
• for example, by feeding you experiences which are
entirely simulated…
– would you be able to escape this imprisonment by false senses?
– would a consistency argument help?
– would a transcendental argument about enabling conditions for
dreaming allow you to refer to prior sensory content?
– would there be any available contrast between dream and
reality?
• what would such an argument show?

20. Modern Demons
Rewrite the Evil Demon Argument in
Standard Form
P1: If I really know that P, then I can rule out
the possibility that there is an all-powerful evil
genius deceiving me about P.
P2: But I cannot rule out the possibility that
there is an evil genius deceiving me.
C: So I do not really know that P.
Other tasks:
Can you update Descartes’ notion of the Evil Demon for
today?
Can you think of any filmic or literary examples?

21. • Supposing the argument to be correct…What
difference would it make?
– If we could not know the difference between the
world of illusion and the real world, would there be
one? (Could we know there was a difference?)
– The sceptical anxiety is predicated on there being a
difference in the first place to be exploited…
• How ‘real’ a possibility might this be said to be?
• Can it be a problem if there is this incoherence?
Responses to the Demon

22. Infallibilism in Standard Form
1. You cannot know what is false
2. So if you know that P, you cannot be mistaken about
P.
3. So for knowledge-claims to succeed, justification must
be infallible.
4. There are infallible justifications.
5. Therefore if I am justified in believing that P, I cannot be
mistaken that P, (and if it is possible I am mistaken that P, then I
cannot be justified in believing that P).
6. So infallibilism is true.
So infallibilism rules out Gettier counter-examples, because
in these cases you do not have justified true belief.

23. A problem with Infallibilism
• Premise 2 is ambiguous: ‘if you know that P, you can’t
be mistaken about P’.
– 2a) (weaker) It could be taken to be a claim about whether you
actually are mistaken: ‘If I make the successful knowledge-claim
that P, it can’t be such that in fact I am mistaken that P.’
• this follows logically from 1., ‘You can’t know what’s false’, and supports 3.
– 2b) (stronger)) It could be taken to be a claim about whether you
could be mistaken: ‘If I make the knowledge-claim that P, I can’t
possibly be mistaken that P.’
• This is a stronger claim still: I am not mistaken, nor can I possibly be
mistaken.
• But it is unfortunately false: there are many cases in which I could make a
knowledge-claim which then failed.
• So 2b) is not a correct inference from 1.
– Yet infallibilism seems to rely on 2b), and is not so entitled.
– So infallibilism is incorrect.