Another Rationalist: Wilhelm Leibniz
Like Descartes and Spinoza, Leibniz (1646–1716) was one of the great rationalists. As with his two rationalist predecessors, he believed that reality is knowable by reason. Leibniz's philosophical system is founded on a small number of basic principles, of which the best known are the principle of sufficient reason and the principle of the indiscernibility of identicals (sometimes known as Leibniz's Law).
The first says that there is a reason that every fact is what it is and not otherwise; nothing happens without a reason. For example, Leibniz argued that because there could be no reason for the world to be created at one moment rather than another, the world couldn't have been created at a particular moment. The second says that if two things are identical, they have all their properties in common.
The Life of Wilhelm Leibniz
Leibniz was a polymath almost without peer. He was a mathematician, jurist, historian, scientist, diplomat, poet, inventor, and courtier. His father was a professor of philosophy at Leipzig University, but Leibniz turned down an academic career. He entered into the employ of Baron Boineburg in Frankfurt, while also continuing his study in the law and pursuing his interest in physics, especially of motion.
Leibniz claimed that all monads were connected with one another. “This connection or adaptation of all created things with each, and of each with the rest, means that each simple substance has relations which express all the others, and hence is a perpetual living mirror of the universe.”
His best-known works are the
Monads and God
Descartes was a
God is an infinitely perfect being who from an infinite number of possible worlds creates the best possible world. He cannot, however, create a perfect world, for that would be logically impossible. To do so he would have to reproduce himself exactly. God is nonextended spirit; thus, a reproduction of his qualities would be indiscernible and so nonexistent. Thus the best of all possible worlds is the one containing as much existence as possible compatible with the greatest degree of perfection. Everything in the universe unfolds according to a pre-established pattern.