Discourse on Metaphysics, Correspondence With Arnauld, and Monadology

"Leibniz was one of the most brilliant thinkers who ever lived, I think, and one of the most interesting philosophers. He wrote many short things, and so Leibniz’s work is often collected into collections. They’re actually surprisingly readable given the abstract nature of the ideas. I would recommend a collection that has two of his great works, one is called the Discourse on Metaphysics , which is an early work of his, and the other is his correspondence with the great philosopher Antoine Arnauld. The correspondence with Arnauld is the best place to begin if you want to understand Leibniz. There’s a connection here with what you just said about Spinoza, but also with Descartes. Descartes thought that the mind and body were two separate substances, and in the notion of substance there is the notion of a fundamental being. The idea that the world contains substances is something that goes right back to Aristotle, it’s an idea about what the fundamental reality of the world is. For Aristotle , a substance was a persisting thing, a thing that continues to exist through change. I think the best way to think of it is that substances are sort of natural unities. The world contains, in a sense, natural unities or a natural order. Descartes thought that there were two kinds of substance, there were the mental substances, which are our souls, whose essence are what he called thought, and then there is the material world itself, and the material world for Descartes was just one substance. It was just one huge extended thing because Descartes identified the essence of matter with extension, by which he meant size and shape, so matter was a purely geometrical idea. The material world around us is fundamentally just one thing, and the material objects we encounter here and there are a kind of arbitrary clumping of matter, so to speak. Material objects have no real unity, and this is very much in opposition to Aristotle’s view where an organism, for example, has a natural unity of its own. Aristotle thought that an artefact, like a table, was not a substance, but that an organism, like a horse, was a substance, because it has a kind of natural unity. Leibniz thought that Descartes had gone a bit too far, and that there was some use for these Aristotelian ideas. In his early work he emphasised that it was important to go back to Aristotelian ideas, like the Aristotelian idea of substance in terms of a natural unity. He thought Descartes’ view of material substance was ok as far as science went, but metaphysics, he said, needed something more than simply the geometrical conception of matter. Leibniz thought that every substance had what he called a complete notion, and the complete notion of a substance was everything that was true of it — absolutely everything. So the fact that you’re sitting here now, the fact that you’re holding the microphone, the fact that you are twenty feet away from the window, all these things are part of your complete notion. In the correspondence with Arnauld, Arnauld raises the question, well if this is true, how could things have been other than they were? How could it have been that you didn’t conduct this interview with me, or that Julius Caesar didn’t cross the Rubicon, because it seems like from Leibniz’s view, if Julius Caesar hadn’t crossed the river Rubicon, he wouldn’t have been Julius Caesar because he wouldn’t have the complete notion of Julius Caesar. Leibniz was fully aware of this question, and what he said was that those things that are necessarily true of you, are those things that you, a finite being, could deduce from thinking about yourself, just from thinking about the nature of yourself. Whereas those things that are contingently true — that are true, but could have been otherwise, like Julius Caesar crossing the Rubicon — those are the things that only God can work out from looking at what he sees about your notion. So he has this very peculiar view about the nature of the reality where it seems as if, in a certain way, things couldn’t have been other than the way they are. If we add to this another element of his view, which is that God must choose the best, then it follows from this that things couldn’t have been better than they are. This is why Leibniz is often accused and mocked as thinking that this is the best of all possible worlds, that things couldn’t have been better than they were. This was the view that was mocked by Voltaire in Candide . Because it’s very funny! I mean a good caricature has to resemble the thing that it’s caricaturing… No, I don’t think so. The way I’ve put it makes it sound slightly frivolous, but in fact what Leibniz was doing was following through the consequences of what seemed to be very simple principles, and if you really want to follow through the consequences of your principles, then you have to accept certain things. Philosophers sometimes do this, but sometimes they’re not very good at doing this, sometimes they just refuse to follow through the consequences, and just say ‘Ah, I couldn’t possibly believe that, but I still hang on to my principle.’ Leibniz’s principle was first that God chose to create this world as it is, rather than in some other way. He also thought that God was wholly good, and that God must choose the best. It follows from that that this world is the best, so if this world contains things that seem less than the best, then we have to understand how that can be so, and Leibniz devoted a whole book to that which was called Theodicy – theodicy here being the explanation of why there can be evil in the world, given the existence of God. It’s an old problem, but Leibniz faced up to it in a way that many religious thinkers don’t. Absolutely. Descartes invented Cartesian coordinates, the representation of geometry that we all learn at school. Leibniz invented calculus, along with Newton. They were both very rigorous thinkers. I actually think philosophically Leibniz was a more rigorous thinker than Descartes, he was more aware. Descartes had more sense in a way. For example, Descartes defined substance as something which was capable of independent existence. It follows from that definition, and other things he believes, that God is the only substance, because everything is dependent on God, so why didn’t Descartes say, as Spinoza said, that God is the only substance? Because he didn’t follow through the consequences of his definition. That’s true, he wanted to be theologically orthodox. What he says, essentially, in his Principles of Philosophy is ‘Ok I can see that this definition sort of implies that God is the only substance, but let’s put that to one side for the moment.’ Sometimes you have to do that in philosophy if you don’t want to end up with these crazy positions like Leibniz’s. There’s the general reasons I mentioned earlier, in connection with reading the great philosophers, and learning about our tradition. In the case of Leibniz, what you see is that he faced up to certain questions about the essence of things, the essence of people, in a way that few thinkers have really faced up to them. Even if you don’t agree with him, it’s really good to ask yourself the question that he’s asking. ‘Was it part of the nature of Caesar that he crossed the Rubicon?’ And you want to say, ‘Well, no, because he might have existed without crossing the Rubicon,’ and you say ‘What makes him Caesar then? What is the essence of Caesar?’ And almost no one has a good answer to that. Now of course one way you could go is to say ‘It’s a ridiculous question, it’s a meaningless question,’ or ‘It doesn’t make any sense.’ But it’s not a ridiculous question. I can easily contemplate how my life would have been if I’d done certain other things, and I’m assuming there that I’m the very same thing. What does that mean for me to be the very same thing? That’s the metaphysical question that you have to face, and it’s raised by Leibniz’s work. He has an answer to it. He provides one extreme view that we have to balance ourselves against, and actually it’s very similar, in many ways, to the views of one of the leading philosophers of the twentieth century, David Lewis. In some ways he had similar views to Leibniz, and Lewis is now someone whose views are widely accepted and followed by people in philosophy."