The philosophy of Gottfried Wilhelm von Leibniz was strongly influenced by two factors, rationalism and Christianity. Leibniz disagreed with Newton that the universe was made up of indivisible elements called a-toms (Greek for "not-divisible"). He believed that the universe was made up of pieces called "monads". In his Monadology, he describes the monads as having no material existence, hence no movement, and no place or time. Each monad had a distinct potentiality, that, when combined with other monads and the directives of God, created material substances. In addition, each monad had a copy or DNA of the entire universe inside it.
Leibniz believed in two different kinds of truths, necessary truths and contingent truths. A necessary truth is one that is true by definition, such as that a child is young. A contingent truth is one that is dependent on other factors, such as "A child comes from a mother." Leibniz, being a rationalist philosopher, wanted to arrive at a base from which to work. He wanted to come down to a base necessary truth to build the contingent truths upon in order to find out the truths of the world. But he found a contradiction - that if everything has a cause, there can be no cause. Since we have no base truth to work from, we can only describe the appearances of events, and their apparent causes, not the ultimate case of anything. He then claimed that all truths ultimately rely on an ultimate cause - God. No explanation can exist without God.
His philosophy that is most relevant to my life is this doctrine of optimism. Last night, I have attended a production of Leonard Bernstein's Candide. Candide is a musical based on the French philosopher Voltaire's satire on the optimism of Leibniz in a novella of the same name. The theme critiqued by Voltaire was Leibniz's "All is for the best in this best of all possible worlds." - a belief started by Leibniz and popularized by Alexander Pope. Leibniz justified the doctrine by creating a model of worlds, starting with the best of all possible worlds at the top, and descending with lesser worlds. Since God is omnibenevelent and omnipotent, he would only choose the best of all possible worlds. And again because he is omnibenevelent, all in this world would be for the best. This is not to say that all is good, simply that it must be so, because it is for the best.