Week 1:
Lecture notes
Rationalists favour reason over all other forms of knowledge.
Knowledge from experience is knowledge which comes from the senses, observation and
testimony whilst reason is the capacity for pure thought.
For example one can know that a triangle’s area is height*base/2 through experience (by
measuring each triangle) or rationally (by doing a mathematical proof…a deductive
argument for a mathematical statement, showing that the stated assumptions logically
guarantee the conclusion)
The debate between rationalists and empiricists is, generally:
To what extent can reason give us knowledge on it’s own?
● Plato (the first empiricist) stated his answer to this question when he said ‘there is
nothing in the intellect that wasent first in the senses’
● Empiricists generally agree that some propositions (such as theorems of logic) can be
known through reason. Although Wittgenstein denys that theorems of logic are
propositions)
● Within rationalism there are differences of opinion as to the extent of what can be
known rationally. There is also differences in opinion as to what type of knowledge it
can reveal.
1. Propositional Rationalism/knowledge about propositions
We can know some important propositions on the basis of reason alone.
● All Swedish aunts are aunts (logical)
● All aunts are female (analytic truth)
● 7 is greater than 4 (arithmatic)
● The diagnols of a parrallelogram meet at their midpoints (geometry)
● Whatever is necessary is possible (modal logic)
● Every event has a cause (metaphysics)
A proposition (in philosophy is a declarative statement. They (and only they) can be
true/false/denied/debated
On the basis of… The gounds upon which we believe something
A posteriori: propositions based partly an experience
A priori not based on experience at all. True even if our senses entirely deceive us. (however
we still need enough experience to have knowledge of concepts)
Propositional rationalists vary on which propositions they feel can be known a-priori
● Descartes and Kant believe that some propositions that are analytic can be known
A-priori (Synthetic A Priori)
● Leibniz’ seems to have felt that all propositions can, in principle, be known a-priori.
As did Hegel. Although neither men believed anyone was clever enough to actually
know all propositions a priori.
One person can know something a priori while others know it a posteriori.
2. Innate Propositional knowledge:
We know some propositions as part of our rational nature, without having to learn them. We
don’t discover them through thought; we remember them.
,Innate propositional knowledge is knowledge that you born with. Any proposition that
can be known with no experiential input is innate. E.g. In Meno, Plato argued that everyone
has knowledge of mathematics because even his slave knew geometry seemingly
immediately.
Innate knowledge is different to a priori. For example we know A-priori that ‘all barking dogs
bark’ but first we have to learn the concepts barking and dog… this requires experience. All
innate propositions are A-priori but not vice versa.
3. Innate Concepts
We possess certain concepts as part of our rational nature. We do not learn them, we are
born with them.
A concept is a mental or logical item, expressed with a common noun or adjective (e.g horse
or red). A concept is produced anytime the subject terms are removed from a proposition
(creating a predicate). E.g. X loves Jill and expresses the concept of loving Jill.
Concepts are different to the thing they represent. E.g a dog can lick you; a concept cannot
lick you.
● In meditation 3 Descartes argues that the concept of God is innate.
● Kant believes that space, time, cause, possibility and negation are innate. We must
have them in order to have any experience in the first place
● Chomsky claimed (looking empirically at children learning their first language that
basic grammatical concepts like nouns and verbs are innate.
Having innate propositional knowledge requires that we have innate concepts but not vice
versa.
Lecture2:
Descartes’ method of doubt: Accept only propositions that are ‘completely certain and
indubitable (destructive stage) and accept only new beliefs that pass it (constructive stage).
What is it for a belief to be ‘completely certain and indubitable’?
● Psychological certainty: maybe we’re psychologically incapable of doubting it.
However, this only shows the strength of my subjective attachment to these beliefs
● Epistemic certainty: there is no chance, given my evidence, that i could be
mistaken about it
Sceptical arguments:
1. There is a certain scenario, which for all I know is possible, on which the relevant
belief would be false
2. I cannot conclusively rule this scenario out (it is consistent with all my evidence
3. The belief could be false, despite all my evidence. It is not certain and indubitable
Descartes evil demon
The conclusion that there is a deceiving demon is weaker than if there was a deceiving god
because the demon cannot deceive our reasoning so our a-priori knowledge is not
challenged.
The God deceiving scenario (where god confounds our reasoning) cannot be disproven, for to
do so would require using our reason. In fact, there is no belief that could be certain and
indubitable.
Descartes doubts a-posteriori knowledge but has faith in our a priori knowledge.
Olsen’s criticism about the method of doubt:
The method of doubt says that we can only accept, as true, propositions that are completely
certain and indubitable.
Is the method of doubt a good one? Consider the 3 assumptions upon which it is based:
, ● No falsehood can ever pass the test.
○ The law of additive velocities: if i am going 50mph north and Ethan is going
50mph south then we will pass each other at 100mph. The law would
probably pass Descartes test. However it does not always hold, for example,
light always has the same speed no matter your relative velocity (Michelson
Morely experiment 1887). The law of assistive velocities is a ‘completely
certain and indubitable’ whilst also being false
● Some propositions pass the test:
○ In order for the method to work it must allow some substantive propositions
will pass the test. Enough for Descartes to use it as the basis for a substantial
body of knowledge. He wants to establish the existence of god and the
immateriality of human beings etc.
● We can tell whether a proposition passes the test
○ What if there is a proposition that seemed to us be absolutely certain and
indubitable but wasent really? Or, if the beliefs that do past the test all appear
to fail it.
○ What if you were to accept only propositions that an omniscient being would
accept? This would give pure truth but we would need to know what an
omniscient being would believe, and for that you would need to know
Descartes’ 1st meditation.
Descartes's meditations are a stream of consciousness in which we follow Descartes through
his thought process. He noticed errors that needed amending. He follows the epistemic belief
that his current knowledge is doubtful. The 1st meditation is the destructive process in which
we see Descartes doubt everything and then in meditations 2 and 6 we watch as he
reconstructs his beliefs from the ground up.
What is epistemic certainty?
‘If there is a scenario, consistent with the appearances, on which a belief would be false, it’s
not certain’
This is a strong sceptical criterion
Realising that he might accept many things to be true which are in fact false; Descartes felt
he needed to completely demolish his beliefs in order that he may rebuild a more secure set
of beliefs. Rather than individually addressing each of his beliefs he decided to analyse his
foundational beliefs and dismiss them (temporarily) if there was any room for doubt. ‘Once
the foundations of a building are undermined, anything built on them collapses of its own
accord’ (P23 S18)
He noticed that any of his beliefs are based on information provided by the senses. He also
noticed that his senses have, on occasion, deceived him (for example a figure far away may
look like a square but is actually a circle). ‘It is prudent never to trust completely those who
have deceived us even once.
Denying the body:
● It is possible to have a dream that resembles everyday life. It is impossible to
confidently distinguish waking from sleeping. Suppose i am in a dream, then the
belief that my eyes or open and my hand is moving might not be true. I might not
even have hands or eyes.
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