Think: A Compelling Introduction to Philosophy

by Simon Blackburn

It is interesting that Leibniz uses a mathematical analogy. It is not just that he was an even better mathematician than Descartes, and amongst other things invented the calculus. It is rather that for Leibniz the whole order of nature must eventually be transparent to reason. When things fall out one way or another it is not just that they happen to do so. There must be, if we could only see far enough, a reason why they do. Things have to make sense. When Leibniz says God does nothing in an arbitrary or unprincipled way he is not really expressing a piece of theological optimism, so much as insisting that we ought to be able to see why things are one way or another. This is his ‘principle of sufficient reason’. In Descartes’s terms, we ought to be able to achieve a clear and distinct idea of why things fall out as they do. We should be able to gain insight into why the way things are is the way they must be. It is this confidence in what ought to be possible to reason that makes Leibniz, like Descartes, a ‘rationalist’.