“Does this mean that you can explain them in terms of monads, Doctor?”
“Not yet. Not in the sense of being able to write out an equation that predicts the refraction of light, or the pointing of a compass-needle, in terms of interactions among monads. But I do believe that this type of theory is more fundamentally coherent than the Atomic sort.”
“Madame la duchesse d’Arcachon has told me that monads are akin to little souls.”
Leibniz paused. “Soul is a word frequently mentioned in connexion with monadology. It is a word of diverse meanings, most of them ancient, and much chewed over by theologians. In the mouths of preachers it has come in for more abuse than any other word I can think of. And so perhaps it is not the wisest choice of term in the new discipline of monadology. But we are stuck with it.”
“Are they like human souls?”
“Not at all. Allow me, your highness, to attempt to explain how this troublesome word soul became entangled in this discourse. When a philosopher braves the labyrinth, and sets about dividing and subdividing the universe into smaller and smaller units, he knows that at some point he must stop, and say, ‘Henceforth I’ll subdivide no further, for I have at last arrived at the smallest, elemental, indivisible unit: the fundamental building-block of all Creation.’ And then he can no longer dodge and evade, but must finally stick his neck out, as it were, and make an assertion as to what that building-block is like: what its qualities are, and how it interacts with all the others. Now, nothing is more obvious to me than that the interactions among these building-blocks are stupefyingly numerous, complicated, fluid, and subtle; just look about yourself for irrefutable proof, and try to think what can explain spiders, moons, and eyeballs. In such a vast web of dependencies, what laws are to govern the manner in which one particular monad responds to all of the other monads in the universe? And I do mean all; for the monads that make up you and me, your highness, feel the gravity of the Sun, of Jupiter, of Titan, and of the distant stars, which means that they are sensitive of, and responsive to, each and every one of the myriad monads that make up those immense bodies. How can they keep track of it all, and decide what to do? I submit that any theory based on the assumption that Titan spews out atoms that hurtle across space and whack into my atoms is very dubious. What is clear is that my monads, in some sense, perceive Titan, Jupiter, the Sun, Dr. Waterhouse, the horses drawing us to Berlin, yonder stable, and everything else.”
“What do you mean, ‘perceive’? Do monads have eyes?”
“It must be quite a bit simpler. It is a logical necessity. A monad in my fingernail feels the gravity of Titan, does it not?”
“I believe that is what the law of Universal Gravitation dictates.”
“I deem that to be perception. Monads perceive. But monads act as well. If we could transport ourselves much closer to Saturn, and get into the sphere of influence of its moon Titan, my fingernail, along with the rest of me, would fall into it—which is a sort of collective action that my monads take in response to their perception of Titan. So, your highness: What do we know of monads thus far?”
“Infinitely small.”
“One mark.”
“All the universe explainable in terms of their interactions.”
“Two marks.”
“They perceive all the other monads in the universe.”
“Three. And—?”
“And they act.”
“They act, based on what?”
“Based on what they perceive, Dr. Leibniz.”
“Four marks! A perfect score. Now, what must be true about monads, to make all of these things possible?”
“Somehow all of these perceptions are flooding into the monad, and then it sort of decides what action to take.”
“That follows unavoidably from all that has gone before, doesn’t it? And so, summing up, it would appear that monads perceive, think, and act. And this is where the idea comes from, that a monad is a little soul. For perception, cogitation, and action are soul-like, as opposed to billiard-ball-like, attributes. Does this mean that monads have souls in the same way that you and I do? I doubt it.”
“Then what sorts of souls do they have, Doctor?”
“Well, let us answer that by taking an inventory of what we know they do. They perceive all the other monads, then think, so that they may act. The thinking is an internal process of each monad—it is not supplied from an outside brain. So the monad must have its own brain. By this I do not mean a great spongy mass of tissue, like your highness’s brain, but rather some faculty that can alter its internal state depending on the state of the rest of the universe—which the monad has somehow perceived, and stored internally.”