Routledge History of Philosophy Volume IV

160 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
These considerations are certainly not the only ones, but they are enough to
make us question the received view. Before we can provide an alternative
reading, however, it will be helpful if we can get a better idea of what exactly
Descartes is rejecting in traditional accounts of method, and what kind of thing
he is seeking to achieve in his scientific writings.
THE REJECTION OF ARISTOTELIAN METHOD
Aristotelian syllogistic was widely criticized from the mid-sixteenth century
onwards, and by the middle of the seventeenth century had been completely
discredited as a method of discovery. This was due more to a misunderstanding
of the nature and role of the syllogism, however, than to any compelling criticism
of syllogistic.
Aristotle had presented scientific demonstrations syllogistically, and he had
argued that some forms of demonstration provide explanations or causes whereas
others do not. This may occur even where the syllogisms are formally identical.
Consider, for example, the following two syllogisms:
The planets do not twinkle
That which does not twinkle is near
The planets are near
The planets are near
That which is near does not twinkle
The planets do not twinkle
In Aristotle’s discussion of these syllogisms in his Posterior Analytics (A17), he
argues that the first is only a demonstration ‘of fact’, whereas the second is a
demonstration of ‘why’ or a scientific explanation. In the latter we are provided
with a reason or cause or explanation of the conclusion: the reason why the
planets do not twinkle is that they are near. In the former, we have a valid but not
a demonstrative argument, since the planets’ not twinkling is hardly a cause or
explanation of their being near. So the first syllogism is in some way
uninformative compared with the second: the latter produces understanding, the
former does not. Now Aristotle had great difficulty in providing a convincing
account of what exactly it is that distinguishes the first from the second syllogism,
but what he was trying to achieve is clear enough. He was seeking some way of
identifying those forms of deductive inference that resulted in epistemic
advance, that advanced one’s understanding. Realizing that no purely logical
criterion would suffice, he attempted to show that epistemic advance depended
on some non-logical but nevertheless internal or structural feature which some
deductive inferences possess. This question of the epistemic value of deductive
inferences is one we shall return to, as it underlies the whole problem of method.
For Aristotle, the epistemic and the consequential directions in demonstrative
syllogisms run in opposite directions. That is, it is knowing the premises from