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A priori knowledge
Michael Lacewing
[email protected]
© Michael Lacewing
A priori knowledge
• A priori: knowledge that does not
require (sense) experience to be
known to be true (v. a posteriori)
• It is not a claim that no experience was
necessary to arrive at the claim, but
that none is needed to prove it.
Analytic and synthetic
propositions
• An analytic proposition is true or false in virtue of
the meanings of the words.
– Not all analytic propositions are obvious: In five days’ time,
it will have been a week since the day which was tomorrow
three days ago.
• A synthetic proposition is one that is not analytic,
i.e. it is true not in virtue of the meanings of the
words, but in virtue of the way the world is.
Rationalism v. empiricism
• Rationalism: we can have substantive a
priori knowledge of how things stand
outside the mind.
– Substantive knowledge is knowledge of a
synthetic proposition. Trivial knowledge is
knowledge of an analytic proposition.
• Empiricism: we cannot.
Empiricism on a priori
knowledge
• For any area of knowledge,
either
– Knowledge is possible, but
empirical, not a priori
– Knowledge is possible and a priori,
but analytic
• Hume: we can only know
‘relations of ideas’ (analytic and
a priori) and ‘matters of fact’
(synthetic and a posteriori)
• Ayer’s verification principle: all
meaningful statements are
either analytic or empirically
verifiable
Locke: religion and morality
• Knowledge of God and moral knowledge
is ‘demonstrable’ and ‘self-evident’
• We know that we exist (synthetic) and
that something cannot come from
nothing (analytic).
• So something must always have existed,
and everything else which exists must
have come from this (analytic).
• As we have knowledge and intelligence,
we may deduce that this original being is
a knowing intelligence (analytic).
• From our knowledge of the existence and
nature of God, and of ourselves as
creations of God, we can deduce what
our moral duties are.
Hume’s response
• Locke’s analytic truths are, in fact, unjustified
assumptions.
• To deny an analytic truth is a contradiction in terms,
e.g. ‘some bachelors are married’. But it is not a
contradiction to deny that something exists, e.g.
that God does not exist.
• So analytic truths can’t tell us what exists.
Kant and mathematics
• Kant argued that
mathematics is a priori, but
synthetic
• Most empiricists argue it is
analytic - we don’t allow
true mathematical claims (2
x 5 = 10) to be false, they are
true by definition
• So maths is a roundabout,
complicated way of saying A
=A
Metaphysics
• Kant: a priori synthetic truths are
about the way experience must be for
us, e.g. ‘Nothing can be coloured in
different ways at the same time in the
same part’
– If this is analytic, it is made true by rules
of language. But is this the (arbitrary)
source of how we experience things?
Rational intuition?
• How could we gain knowledge of
‘metaphysical’ truths? ‘Reason’
• But how does ‘reason’ work here? What
is rational ‘intuition’ into how things
are? Is it reliable?