Perhaps
BonJour goes the furthest towards the kind of rationalism we would
recognise from the Rationalists of the late 17th and early 18th
centuries. Nevertheless, there are substantial differences between
BonJour’s work and these philosophers. The principle
difference, to my mind, is BonJour's acceptance of the possible
experiential/empirical defeasibility of a priori claims,
‘reasons’ and beliefs.
Is
Thought Itself A Priori?
BonJour
argues that in reasoning one can't ever rely solely on experience.
Even in the case of reasoning about premises which are empirical or
experiential, something a
priori is required to be added to the reasoning process.
BonJour
particularly talks in terms of the relations between the antecedent/s
and consequents of arguments (or claims). His position comes in three
parts:
i)
“If all the things for which there are direct
experiential reasons are already contained in the antecedent.
ii)
“and if the consequent genuinely goes beyond
the content of the antecedent.
iii)
“then experience can offer no direct reason
(and no indirect reason without assuming some other conditional of
the same sort) for thinking that such a conditional proposition is
true.” [2008]
What's
being stressed here is that the a priori move (or inference) –
i.e., from the antecedent to the consequent - can't itself rely on
experience. Experience itself doesn't provide the grounds for such a
move.
What's
stated in i) to ii) BonJour argues can be said of all reasoning and
indeed of thinking itself. If the a priori is rejected, it will
lead to
“a
deep and pervasive version of scepticism, one in which we have no
reason for thinking that any of the various seemingly empirical
claims that are not directly justified by experience are true”.
[2008: p. 102]
The
point which is repeatedly made by BonJour is that even if our claims
or premises are empirical (indeed even if they're directly or fully
empirical), the empirical or experiential itself can't account for
the transitions between these empirical/experiential premises and
other empirical claims or conclusions.
It
can of course be said that such logical moves have been made - and
experienced - before and that's an empirical fact. Despite
that, experiencing logical moves (in the past) and the logical moves
themselves aren't the same thing. We can make an inductive inference
about the kinds of moves "average reasoners" make; though that won't
tell us anything about the move itself or whether or not it's a
priori in nature.
The
basic point is that conditionals, for example, can't be shown - or
known - to be true by recourse to experience itself; even if the
antecedent and the consequent of a conditional are themselves
empirical/experiential in nature.
According
to BonJour, naturalists and Quineans do believe that
“we
never have a priori
reasons for thinking that if one claim or set of claims is true, some
further claim must be true as well”. [ibid., p. 103]
If
such people do believe that, then what does BonJour think will follow
from this? He believes that
“there
is simply nothing that genuinely cogent reasoning could consist in...
the rejection of a priori
reasons is tantamount to intellectual suicide”. [ibid., p.
103]
What is
BonJour’s problem? Why these severe words? If a priori
logical moves are really necessary and fundamental, then even if
Quineans reject the a priori in word - they won't do so
in deed. After all, BonJour has already argued that they can't
do so. Thus there couldn't be any such thing as “intellectual suicide”- according to
BonJour’s own lights!
Reference
BonJour,
Laurence. (2008) 'In
Defence of the a Priori', in Contemporary Debates in
Epistemology (edited by Matthias Steup and Ernest Sosa).
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