Monads described above are monads for formula 118. The pure functional programming language Haskell implements them using monads, derived from category theory. Alternatively, one can describe algebraic structures using monads. Leibniz's best known contribution to metaphysics is his theory of monads, as exposited in "Monadologie". A more recent philosophical source of perspectivism is Leibniz's theory of monads. Specifically, Leibniz writes a potential false premise in his definition of how monads interact. The do-notation eases working with monads. He builds this idea of monads, connecting ideas with logical reasoning and explanation where needed. Leibniz is also known for his theory of monads, as exposited in "Monadologie". Monads present opportunities for interesting techniques beyond just organizing program logic. These simple substances or monads are the "ultimate units of existence in nature". They are sometimes used for doing I/O operations in functional languages in lieu of monads. In his monadology he advances a sophisticated novel argument for the immortality of monads. Monads are the ultimate elements of the universe. There are many types of monads, each one solves a particularly common issue.