Leibniz constructed a large interlocking metaphysical system.
IT seems that the best place to start with Leibniz is with his understanding of the monad.
Leibniz argued that reality is composed of elements, which he called monads. The term "monad" was used by Leibniz to designate a single unit, which constituted a simple component of reality.
The real world for Leibniz was composed of these spiritual entities that Leibniz designated as monads, which existed from the most important one, God, down to the human soul and further down to what we conceive of as matter.
Leibniz contended that everything complex must be analyzed into simpler elements and that sooner or later we will arrive at a level of reality, which is no longer analyzable.
Interestingly one of the most influential doctrines of the 20th century world of physics contended that all matter is constituted by energy.
Leibniz it seems was moving toward this conclusion in arguing that monads are centers of activity.
In a sense Leibniz was a very modern thinker.
One of the most striking dimensions of Leibniz thought centers in his contention that all meaningful statements must be of one or two kinds.
On the one hand, he argued that there is a type of statement that is true by definition, such as the statement "all bachelors are unmarried males" and on the other hand he further argued that there is a type of statement which is knowable only by experience such as the statement "a monkey is in the next room," which is confirmable only by going into the room to observe.
One statement is true by definition while the other statement requires experience.
Leibniz was the first to expound this distinction clearly.
