Leibniz was a bright fellow; for one thing, independently of Newton, he invented the calculus. But for a bright fellow he certainly had his share of screwy ideas. He saw there was a problem understanding the relationship of mind and matter, so he proposed that both were constructed of the same substance, which he called "monads". This dodge sounds to any sensible person as though it only needlessly complicates the issue. But it is always a convenient philosophical trick to evade difficulties by introducing new difficulties.
Another question that Leibniz applied his powerful mind to is the the old "problem of evil" which dates back to Epicurus. Since God is supposed by Christians to be all good, all knowing, and all powerful, there should not be any evil in the world he created—but there obviously is. How to explain away this embarassing fact? Leibniz suggested that though there may be evil in the world, that overall this is the best of all possible worlds (and we should therefore let God off the hook). But really! This is the best of all possible worlds??? Voltaire found this notion amusing and wrote an influential book criticizing it (Candide). It is harder to say if the following item is supposed to be ridicule or not: