 Hi, I'm Peter Adamson and you're listening to the History of Philosophy podcast, brought to you with the support of King's College London and the Leverhulme Trust, online at www.historyofphilosophy.net. Today's episode? By the Time I Get to Phoenix. Avicenna on Existence. I can't believe I haven't yet told you about my sister. She's a few years younger than me and also used to study philosophy, but she wanted a more exciting life and ran off to join the circus. Before long she became a skilled trapeze artist and married the bearded lady. After some initial confusion, the marriage was annulled. Her restless spirit led her to quit the circus though, and she moved into my basement, where she spends most of her time writing the scripts for this podcast, which I pass off as my own. Oh, one other thing you should know about my sister, she doesn't exist. I have never had a sister and, barring some very surprising news, am never going to have one. Yet it seems pretty clear that this sister of mine could exist. Everything I told you about her would be, if not likely, at least possible, well, apart from the idea that anything could be more exciting than philosophy. It isn't just my trapeze artist basement-dwelling sister who doesn't exist, but could have. There are an infinity of things that will never exist, even though they apparently could quite easily exist. They needn't be people. Unicorns and centaurs, the fourth of the five moons that are orbiting around the earth, the trophy that my favorite football team Arsenal won in the last five years. It seems obvious that such things could have existed, yet they never will. Then on the other hand, there are the things that do get to exist, but might just as easily not have existed. You and I, and every human who has ever lived or ever will, will fall into this category. In fact, if you look around you, you won't see anything that absolutely had to exist. Rather, the world is full of what philosophers would call contingent things. To call something contingent is just to say that it is neither necessary nor impossible. An impossible thing would be, for instance, a round square, or an activity even more worthwhile than philosophy. And what would a necessary existent be like? Let's set that aside for now, we'll talk about it as soon as my non-existent sister has written the next script. Philosophers refer to necessity, contingency, and impossibility as modal concepts, and to the whole phenomenon as modality, because these are three modes that can apply to things or to statements. You might find it strange to think about existing things in this context, and quite a few modern-day philosophers would agree. For them, it would be statements or propositions that are characterized by necessity, contingency, or impossibility. You can best think about this in terms of truth. A necessary proposition is one that is guaranteed to be true, an impossible proposition one that must be false, a contingent proposition one that might be true or false. For instance, I have a sister who was a trapeze artist. It's false, but could have been true. We already find this in Aristotle, minus the examples about trapeze artists. He talks quite a bit about modality in his logical works. He tells us, for instance, that if the two premises of a syllogism are necessarily true, then the conclusion that follows from them will also be necessarily true. We even saw modality turning up in his epistemology, when he said that knowledge in the strict sense must involve necessary truths. This was an aspect of Aristotle's logic that particularly interested Avicenna. His own extensive writings on logic respond to Aristotle and to his commentators, up to and including Al-Farabi. I've mentioned that Avicenna seems to have respected Al-Farabi more than any other predecessor who wrote in Arabic. Notwithstanding the story Avicenna tells about finally understanding the metaphysics thanks to Al-Farabi, his respect was based largely on their shared interest and expertise in logic. But as usual, Avicenna's respect for and use of his predecessors from Aristotle onwards didn't prevent him from putting forth innovative ideas of his own. Logic was certainly no exception. As I said last time, in the Islamic world Avicenna effectively replaced Aristotle as the author whom most personified philosophy. This was especially true in logic, since theologians and others trained in the later madrasa educational system were brought up on a diet of Avicennan logic, much as the philosophy students of late antiquity had begun with the Aristotelian Orgadon. Some of Avicenna's influential ideas in logic have to do precisely with the modal notions I've been discussing—necessity, contingency, and impossibility. As you might remember, Aristotle's own ideas about this were somewhat puzzling. On the one hand, he strenuously insists that there are some things that could be the case—could exist, could happen—but don't. He scornfully refutes a group of philosophers called the Magarians, who believe that there is no such thing as unrealized possibility. As Aristotle points out, this would eliminate the difference between being blind and just not seeing anything at the moment. In fact, it's perfectly possible to be able to see without actually seeing, for instance because one's eyes are closed. On the other hand, Aristotle argues in other contexts that what is eternally the case is also necessarily the case. For instance, he believes that if the heavens exist eternally, then it follows that they exist necessarily. That may be a seductive thought, but notice the apparent implication. If it is eternally the case that something doesn't exist, then it necessarily doesn't exist. In other words, my sister, who never has existed and never will, turns out on this theory to be impossible. That way of thinking of things seems unfortunate from our point of view, but generations of logicians and metaphysicians in antiquity and the early medieval period tended to work with precisely this way of thinking. It is sometimes called the statistical, or frequentist, view of modality. According to this statistical view, to say that something is impossible is nothing more nor less than saying that it never occurs, and to call something necessary is just to say it always occurs. Rather uncomfortably, this leaves us with only one remaining option regarding the contingent things in the middle, we'll have to say that they sometimes occur, but not always. For instance, to say it is contingently true that a human sleeps would be to say that sometimes humans sleep and sometimes they don't. That sounds okay when you apply it to general types of things like humans. Probably if no humans anywhere ever went to sleep, we would indeed be tempted to conclude that it is impossible for humans to sleep. But if you apply it to individual things that don't occur, it looks much less plausible. As I say, it doesn't seem to follow from the fact that my sister never exists, that she couldn't possibly exist. Nowadays, the statistical view of modality is long dead, and Avicenna helped kill it. In his logical system, it remains the case that propositions have statistical implications, even if they may seem not to. In fact, he criticizes philosophers like the members of the Baghdad school for overlooking this point. For instance, if I say the giraffe is tall, Avicenna would take this to imply that the giraffe is tall at some time or other. However, he also ties modality to the natures or essences of things. For instance, if I say that it is possible for humans to be trapeze artists, that will mean that it is compatible with human nature to be a trapeze artist. This will apply to every human, including humans like me who wouldn't even consider attempting to become a trapeze artist. Thus, we can now apparently say that there are some things that could be the case, but never are. So far, I've been talking about this as if it were solely an issue of logic, but it is also an issue about what exists, an issue of metaphysics. What might go so far is to say that for Avicenna, it is the issue of metaphysics. Therefore, just as it is compatible with my nature for me to be a trapeze artist or not, it is also compatible with my nature to exist or not. Here, we have arrived at what may be Avicenna's most famous philosophical distinction, the distinction between essence and existence. He makes the point with the example of a triangle. If you just consider the nature or essence of a triangle, and if you were paying attention in geometry class as a kid, you'll be able to see that a number of things follow from that essence. For instance, it must have an odd number of sides, and it must not be round. If you were paying more attention than I was, you might even be able to deduce that its internal angles are equal to the sum of two right angles. But one thing the essence of triangle will not tell you is whether it exists or doesn't exist. So here is something I share with triangles, albeit not the only thing, for instance they don't have sisters either. Both the triangle and I are contingent existence. This simply means that we have essences that are compatible with both existence and non-existence. In this we are unlike, say, round squares or carnivorous giraffes. These things cannot exist, because their essences preclude their existence, which is just to say that they are impossible. That's pretty obvious with the round square, since its being round will prevent it from being square and vice versa. We might express the point by saying that supposing the existence of such a thing would yield a contradiction. You might object to my other example though. You might insist that you're perfectly able to imagine a meat-eating giraffe, so this can't be an impossible existent. But I think Avicenna would disagree. As any good Aristotelian knows, it is essential to giraffes that they be vegetarian. The test for metaphysical possibility is not sheer conceivability, but what is compatible with the essence of a thing. Hence, not only are round squares impossible, but also non-rational humans and carnivorous giraffes. As a side note here, you might recall that there is a logical category called the proper accident, which is an accidental feature shared by all members of a species. The standard example is the ability to laugh, which belongs to all humans at all times. With his notion of essence, Avicenna can now explain very nicely what this means. Even though all humans can in fact laugh, something could still have a human essence, even if it lacked the ability to laugh. It just wouldn't be much fun at parties. By contrast, rationality is actually part of the human essence, so non-rational humans are genuinely impossible. The upshot of this is that we can envision three kinds of things. Existence that are necessary, contingent, and impossible. They have these modal features because of what their essence tells us about whether or not they exist. An impossible thing has an essence that rules out its existence. A necessary thing would have an essence that guarantees its existence. So far we haven't talked about whether there is anything like that, but spoiler alert, Avicenna thinks there is, as we'll find out next time. In between would be what in Arabic is called al-mumkin, the possible or contingent. Avicenna speaks of such things as having essences that neither deserve to exist nor deserve not to exist. Obviously, pretty much everything that does exist falls into this category. As I said, if you just look around, you'll find nothing but contingent things as far as the eye can see or the mind can contemplate. For Avicenna, such things need to be, as he puts it, preponderated to exist or not to exist. Since they do not exist under their own steam, so to speak, they will require something else to bring them into existence, if they are going to exist. This is what it means for one thing to be a cause of another, or at least a cause of its existence. With all these distinctions in hand, it would seem that Avicenna is in a position to give a straightforward metaphysical account of my non-existing sister. She could exist, but she doesn't. This should mean that her essence is compatible with existence, but unluckily for her, she has not been preponderated to exist. Here though, things get a bit tricky. Avicenna says in several contexts that those things that never exist at all are impossible. Gives the example of the mythical bird known as the phoenix. This looks like a mistake. Really what he should say is that there are two kinds of things that never exist. First there are things like round squares. As I said, these would be things whose essence immediately rules out their existence. But then there are also things that might have existed, but don't, like the phoenix. Why would Avicenna also call these items impossible, as if they were like round squares? Well, Avicenna himself had something in common with triangles, he was pretty sharp. So it's unlikely that this is just a mistake on his part. In fact, there are several reasons he might want to say that all the things that never exist and not just obvious absurdities like round squares are impossible. For one thing, there is more than one way to exist. So far we've been thinking about what Avicenna calls external or concrete existence, that is existence out there in the world. But he also has the notion of mental existence. In this sense, my sister on the flying trapeze does exist. We've been thinking about her for a good 15 minutes or so, so she exists in our minds. By contrast, something that really didn't exist at all would be something that never existed in any mind, anywhere, at any time. Perhaps because the mere thought of it would be absurd. That would give Avicenna a good reason to say that something that never exists must be impossible. If it really never exists, not even in the mind, then it must be inconceivable and hence impossible. Unfortunately, this is definitely not Avicenna's rationale. When he talks about the Phoenix example, he explicitly says that although it is impossible, it does have mental existence, which is actually pretty obvious. People do think about Phoenix's after all, though not as often as they used to. According to Avicenna, then, even things that are impossible can have mental existence, they just can't exist in concrete reality. So, let's try something else. Think back to what I said before about the two kinds of impossible things. Some like round squares must be non-existent by virtue of their very essences. Merely to suppose that such a thing exists would land you in absurdities. Not so for the Phoenix. No contradiction would arise if there were such a bird. But it might be impossible in a different way. Something apart from its essence might prevent it from ever existing. As we'll see next time, Avicenna talks about things that are contingent in themselves as being made necessary through another, that is, given a kind of guaranteed existence thanks to an external cause. So the converse might be true for things that are caused not to exist. They may in fact be contingent in themselves, but impossible through another. For instance, perhaps God prevents them from existing by not including them in his providential plan for the universe, in which case they are prevented from ever coming to be. Again, this would apply only to concrete existence in the world. The Phoenix seems possible to us, and it has mental existence, because we think about it, but God has arranged the world in such a way that the Phoenix can never be real, and it in that sense it is impossible. Here it's worth remembering that in and of itself, a contingent thing neither deserves to exist nor not to exist. Neither existence nor non-existence will be a default situation for it, rather it will have to be preponderated one way or another. So for every contingent essence, there are two ways things could go. Either there is a cause that makes it exist, in which case it necessarily follows that it will exist, and then it is necessary through another. Or there is a cause that makes it not exist, in which case it is rendered impossible. I should hasten to add that Avicenna doesn't spell this out the way I've just done. In particular, he doesn't give us the nice distinction between two kinds of impossible things, the absurd ones like round squares and the apparently possible ones like Phoenix's. He just says that in general, what never exists is impossible. The line of thought I've just sketched though would explain why he says that. Some things that never exist could have, but were caused not to. Others could not have been caused to exist, even by God, because they are intrinsically absurd. And both kinds are in a sense impossible. But the first kind, like the Phoenix, is made impossible by the chain of causation that ultimately flows from God, which prevents the thing from existing. The second kind, for instance the round square, is impossible all by itself, because the thing's own essence guarantees that it will never exist. This solution prompts the following question. What does God have against my poor sister? Was it really part of God's providential plan to exclude her from the universe, along with those other unfortunate people who don't exist? This seems a bit harsh, especially since I could really have used her help writing these podcasts. It is more likely though that Avicenna is not thinking of the whole issue at such a fine level of detail. After all, humans all share the same nature, as would all Phoenixes if they existed, albeit that only one would exist at any given time, according to legend. Avicenna's deliberations about what is and is not possible, then, are probably at the level of the universal, and not the particular. Not me and my sister, for instance, but the universal type, human being. This relates to one of Avicenna's most controversial philosophical discussions, which concerns precisely this question of how God relates to particulars. After all, if God didn't go out of His way to make my sister not exist, then apparently He also didn't make any special effort or decision to make sure that I do exist. Does God's providence even extend down to the level of particular things? Or is He only concerned that the right types of things exist? In that case, He providentially ensures that there will be humans, but not Phoenixes, while giving no attention to the question of which humans exist and which don't. We'll have a chance to get into this issue next time, as we turn our attention to Avicenna's philosophical account of God. At least as much as his work in logic, this will prove to be an area where Avicenna exerts tremendous influence on subsequent philosophers in the Islamic world and beyond. At the core of his theory is the identification of God with wajib al-wujūd, the necessary existent. Already in this episode, we wondered a couple of times whether there is anything that exists necessarily. Avicenna thinks he can prove that there is indeed a necessary existent, and that this necessary existent can be shown to have all the traditional attributes associated with God. How does he prove these things? To find out, it will be necessary for you to listen next time, for Avicenna on God, here on The History of Philosophy, without any gaps. God bless!