The chief aim of the world is this, that we should  cognize the perfection of God from it. Now if God would attain this  aim, he also had to arrange the world in such a way that a rational  being could extract from the contemplation of it grounds that would  allow him to infer with certainty the properties of God and what can  be known about him. (Rational Thoughts on the Aims of Natural  Things, §8, p. 6) 