What the heck is a monad?

Good question. I wonder if Leibniz himself had any clue himself. At any rate, he certainly says a lot of something in his Monadology.

As far as I can tell, monads are to metaphysics as atoms are to the natural order. They are the elementary particles of… everything, utterly simple and indivisible. Naturally, they are eternal and indestructible without divine intervention. When brought together, they form composites. Each is wholly unique. Monads cannot be affected by any outside influence. As such, all cause and effect relationships are illusionary. All are capable of perception, and “see” the universe from their own unique perspective, yet not all monads are minds. Some monads are minds, though. I am a monad, and even God is a monad, the perfect, unlimited monad. In reality, the myriad of monads that is the universe could not be any better. All chaos and apparent evil are really a matter of blurred perception, for “nothing is confused in itself—what’s happening here is that you are perceiving confusedly” (69).