Leibniz is a 17th century rationalist and Berkeley is a 18th century empiricist. Leibniz uses math and reason in his knowledge, goes step by step toward his conclusion, and he is missing experience. Berkeley, on the other hand argues that earlier philosophers used words that they themselves did not understand and his philosophy begins in experience. .
In his first paragraph, Leibniz talks about monads. He describes monads as simple substances or "without parts." Here he uses reason to analyze the universe. He describes that in analyzing the universe, we reach a level where we can't cut or divide it anymore. This is the point at which it stops. He calls this the atomic theory: although we don't see atoms, we know they exist through reason, and because there are compounds, there must be simple substances that make them up. These are monads, and these monads are real atoms of nature, or elements of things. These substances don't have to have a body because substance isn't a body. We cannot create or destroy them which leads to the idea of God. .
God could create or destroy them because God could create or destroy anything. The universe is the aggregation of monads. Monads have no windows. They are unrelated and cannot connect with other monads. They are atomic un-relatable units. Each atom is in a world in itself. The basis of relationship between each monad is God. He fits them together in the best possible arrangement. Therefore, of the possible worlds, God does not have replication; in nature there are no two things alike. .
This leads Leibniz to spin out his philosophy from sufficient reason. Principle of sufficient reason: there is reason for everything. There be no fact real or unreal without sufficient reason. In this principle, Leibniz is missing experience. This leads him to two truths. The first being reasoning-things are necessary ( x must be y). The second is fact-things are contingent and their opposite is possible ( x may or may not be y).
