The best books on Neoplatonism

What is Neoplatonism?

The term ‘Neoplatonism’ was coined in the 19th century to describe a school of thought in late antiquity, starting with the philosophy of Plotinus in the 3rd century AD. The members of this school were all followers of Plato, and they would have described themselves simply as Platonists. The 19th-century scholars who coined the term ‘Neoplatonism’ thought that there was something distinctive about Plotinus and his successors as compared to earlier followers of Plato, but many modern interpreters think that the use of the term exaggerates the extent to which Plotinus and his followers differed from earlier Platonists.

Plato emphasised the difference between appearance and reality. Reality was not as it seemed, but was constituted by the Forms, which had some kind of universal existence independently of the world we perceive with our senses. Is that the key aspect of Plato’s thought that comes through in Neoplatonism?

Yes, that is certainly an important part of it. The Neoplatonists distinguish between the world of Forms and the perceptible world. Forms cannot be perceived, but they can be known (that is, they are ‘intelligible’ or understandable). The things that we perceive with our senses (‘sensible’ or ‘perceptible’ things) are dependent on the Forms. For the Neoplatonists, reality has a hierarchic structure, in which the lower, sensible things are in some sense derived from the higher, intelligible things. The higher things are more unified, more valuable, and less involved with bodies. Bodily things are low down in this hierarchy because they are changeable, perceptible, and temporally and spatially extended. Forms are higher up. They are not subject to change and are not spatially extended or bodily. At the very top of the hierarchy is the Good or the One, which is entirely unified and simple. Interestingly, we are somewhere in the middle of this hierarchy. The human soul is not bodily or perceptible, but it is subject to change. It is intermediate between the realm of bodily things and the perfect realm of Forms.

Does this have a religious tinge, because that sounds very close to a Christian picture of the body’s imperfections and the soul’s perfections?

There is certainly a religious aspect to this. The Good (also sometimes called ‘the One’) is divine. There is one supreme divinity, although the Neoplatonists also acknowledged the existence of lesser divinities within the hierarchical structure. It is no accident that this description of Neoplatonist views about the soul and the body reminds you of Christianity. The Neoplatonists weren’t Christians, although they were active in the Christian era. But they had a lot of influence, both on Christian thought—on Augustine for instance—and also on Islamic thought.

That’s really interesting. Could you give me a kind of list of some of the key Neoplatonist thinkers, so we know the people we’re talking about—not just the ones that you’re going to mention?

Yes. As I’ve said, the first person we classify as a Neoplatonist is Plotinus. He lived in the third century. Plotinus’s pupil Porphyry was an important figure who edited Plotinus’s books and wrote a life of Plotinus. We know a bit about Plotinus through Porphyry. Porphyry also wrote works of his own, including “Against the Christians”, which has not been preserved, and a work on vegetarianism, which will be one of my five books. Porphyry’s pupil, the Syrian philosopher Iamblichus was another important figure. He was very influential on later thinkers, though his work is now preserved mainly in fragments. Hypatia was a female philosopher and mathematician, based in Alexandria. She is said to have been killed by a Christian mob. Unfortunately, none of her writings survive, but it is interesting to note that women were able to achieve prominent positions in Neoplatonist circles. Proclus, based in Athens in the fifth century, was a great systematiser. He wrote numerous commentaries on Plato, but also systematic works of philosophy of his own. Later Neoplatonist philosophers were mainly based in Athens or Alexandria. They included Damascius, who was the last leader of the Athenian school, and Damascius’s disciple, Simplicius, who is mainly known for his commentaries on Aristotle.

So they embraced both Plato and Aristotle?

The relation to Aristotle is quite interesting. Plotinus and Proclus are often critical of Aristotle, but some other Neoplatonist philosophers argued that where Plato and Aristotle seem to disagree, the disagreement is really only apparent. One strategy for defending this view was to say that the disagreement was ‘in words only’: the two philosophers had the same view, but used different words to express it. For instance, one apparent disagreement is over self-movement. Plato says that the soul is self-moving, whereas Aristotle denies this. On Aristotle’s view, an animal’s soul moves its body, but the soul is not itself moved. That looks like a real disagreement. But certain Neoplatonists said ‘Oh well, that’s just because Plato and Aristotle mean something different by “movement”. In Plato’s sense of “movement”, Aristotle would agree that a soul can be moved.’ Defending this kind of claim involves some creative and interesting interpretation of Plato and Aristotle.

Sounds more like Derrida to me. You’ve written a book about Neoplatonism. What’s that about?

My book is called Freedom and Responsibility in Neoplatonist Thought. I explain how the kinds of questions the Neoplatonists discuss arise out of earlier thinking about freedom and responsibility. Often these questions aren’t quite the same as the questions that naturally occur to us, although they overlap in various ways with modern concerns.

The Neoplatonists have a very demanding notion of freedom. Something that is free must be unhindered in its pursuit of the good. To be free one must be one’s own master, not dominated by anything else. The Neoplatonists argue that only something that is perfectly good can be free in this sense. This raises a question about whether anything other than their highest divinity, the One, can really be free, and it also raises questions about responsibility. If being free involves being perfect, then normal human intentional action, especially bad action, doesn’t count as free action. How, then, can it be right to hold us responsible for what we do when we act badly? A similar question arises for Plato, given his claim that no one voluntarily does wrong.

“For Plotinus, philosophy is not only an intellectual exercise but also a way of life”

Neoplatonist answers to these questions often invoke notions of self-reflexivity. For instance, they argue that being free involves being self-determining and self-knowing, and they argue that human beings are responsible for what they do because they have a capacity for self-reflection. These arguments raise further questions. Is self-determination really possible, and if so, in what sense? What is it to know oneself? Rationality is often thought to distinguish human beings from other animals. Is there some important connection between being rational and being self-reflective? And if so, does this explain why humans are responsible for their actions in a way that other animals are not? Those are the sorts of questions I discuss in my book.

Those questions are questions at the heart of the current freewill debates, actually.

Yes. I think there are interesting connections with modern freewill debates – especially with those modern discussions that emphasise the ways in which one’s freedom can be compromised by things that are internal to oneself. But there are also important differences, partly because the Neoplatonists are approaching these questions from such a different philosophical background. For instance, the idea that being embodied is an impediment to freedom is alien to most modern discussions.

Let’s go to your first book choice, Plotinus: An Introduction to the Enneads by Dominic O’Meara. 

This is a very short and accessible introduction to Plotinus. One of the things I really like about it is that it brings out the excitement of Plotinus. It doesn’t just tell you what he thought. It looks at his ideas in a way that engages with the philosophy and isn’t afraid to ask, ‘what could Plotinus possibly mean by this highly metaphorical language? Can we really make sense of it?’

Another thing that I like about this book is that each chapter points the reader to a relevant chapter in Plotinus. This means that the book connects you with the text so you can explore it for yourself. O’Meara does this very well. So the book gives you a lively introduction to what’s exciting about Plotinus, what’s puzzling or peculiar about him, and it also encourages you to go and read Plotinus yourself to see what O’Meara is talking about.

I would also like to mention here two other books that are not among my five, but that are nicely complementary to O’Meara’s. One is Eyjólfur Emilsson’s Plotinus, which is similar in scope and aim to O’Meara’s book but slightly more advanced. It would be a good thing to read after O’Meara. The other is Pierre Hadot’s Plotinus or the Simplicity of Vision (in the original French, Plotin ou la simplicité du regard). Hadot is especially good at bringing out the way in which, for Plotinus, philosophy is not only an intellectual exercise but also a way of life: a means to self-improvement and self-transformation.

O’Meara’s book is a commentary on The Enneads. What does that mean? And what’s the main thrust of the Enneads?

Plotinus wrote on a wide variety of themes within metaphysics, psychology and ethics. All of Plotinus’s writings were collected and edited by his student Porphyry, who called the collection ‘the Enneads’. ‘Enneads’ means ‘nines’, and the name reflects the fact that Porphyry arranged Plotinus’s writings thematically, into six books, each including nine shorter treatises. There are some places where Porphyry’s attempt at thematic arrangement pulls apart things that one might think should be kept together. However, Porphyry also recorded for us the order in which these treatises were written, so as well as having the order in which Porphyry arranged them, we also know the order of their chronological production.

Porphyry sounds like a combination of Boswell (who wrote a biography of Samuel Johnson) and Henry Hardy (the scholar who edited Isaiah Berlin’s works posthumously).

Yes, Porphyry also wrote a short life of Plotinus, which tells us some interesting details about him. Of course, we can’t be sure how reliable it is. Porphyry wanted to paint a particular picture of his own relation to Plotinus. But it’s interesting to have the little details that we get from that portrait.

Let’s move on to the second book, Neoplatonism by Pauliina Remes.

This is a more general book on Neoplatonism, going beyond the writings of Plotinus. It’s very hard to write a good general introduction, because a lot of the writings are quite abstruse. Remes’s book does a really good job of bringing out what’s philosophically interesting about the Neoplatonists. Each chapter focuses on a particular theme. In each case, Remes starts off with Plotinus on the topic, and then goes on to discuss later Neoplatonist reactions to, and disagreements with, Plotinus.

The disadvantage of this approach is that it foregrounds Plotinus in a way that sometimes underplays the importance of later Neoplatonists, especially when they are not simply reacting to Plotinus. But as an introduction, the book has the great merit of giving you a grounding in Plotinus, and telling you something about how these later Neoplatonists reacted to or disagreed with him. Learning about these disagreements also helps one to engage philosophically with these works oneself.

Remes is very good at bringing out why the Neoplatonists have interesting things to say to us today, and why modern philosophers should pay attention to them. One consequence of this is that, compared to some other writings on the Neoplatonists, Remes downplays aspects of Neoplatonist thought that seem especially weird to us nowadays, in particular some of the religious and ritualistic aspects. But this book provides a wonderful introduction to the Neoplatonists for anyone who has general philosophical interests and wants to explore their thought.

I studied philosophy and never knowingly read any Neoplatonic text – I barely read any Plato, but Plato and Aristotle were on the syllabus. Neoplatonism doesn’t tend to be on a philosophical syllabus in most philosophy departments. Is that because it’s particularly difficult or is there some other reason, do you think?

I suspect the Neoplatonists might figure more prominently in France or Italy, and there are also interesting connections with German Idealist thought. It seems to me that the philosopher who really should be on the syllabus is Plotinus. I think the fact that he’s not studied much in modern Anglophone departments is partly a matter of fashion, but there are also reasons why his work might not appeal to a certain type of modern analytic philosopher. Firstly, Plotinus’s views are quite weird, and his general approach would seem obviously misguided to modern philosophers who presuppose naturalism or physicalism. Secondly, much of Plotinus’s work is reacting to earlier philosophers, so it is hard to understand what he is up to without having some knowledge of his predecessors. And thirdly, his writing style is very different from that of a modern analytic philosopher.

It might be useful at this point to say what kind of a writer Plotinus is. Porphyry tells us that Plotinus had very bad eyesight. For this reason, he tended not to re-read his writings and revise them. Perhaps partly because of this, when you read a bit of Plotinus, it’s as if you’re thinking through a problem with him. This is something I find exciting. He has a very discursive way of writing. It’s almost as if he’s written a dialogue, except without indicating when he is switching from one speaker to another. He will explore one idea for a bit, but then ask, ‘on the other hand, what about this?’ It isn’t always obvious, in any one part of the text, whether what you’ve got is something that Plotinus is asserting, or instead something that he’s putting forward as a position someone might hold, a position that he is then going to qualify or even refute.

You could be describing Ludwig Wittgenstein in the Philosophical Investigations. That’s almost exactly what he does.

Yes, there is perhaps something in common with the style of the Philosophical Investigations. Once you’ve got the hang of what Plotinus is doing, you feel as if you are thinking things through with him.

Is this a pedagogic technique that is forcing the reader to think for him or herself? That’s what Wittgenstein always said about his own approach.

It certainly does have this effect. I suspect that Plotinus’s writing has this discursive character because it arises out of his discussions with his pupils. The fact that Plotinus was so immersed in Plato’s dialogues may also have influenced his way of writing.

Your remaining three books are primary texts. Which is the first of those?

The first is one of Plotinus’s works, Ennead VI.8, On the Voluntary and the Free Will of the One. There is a good recent translation, with commentary, by Corrigan and Turner.

Ennead VI.8 deals with two connected sets of questions about freedom: questions about what it is for human beings to be free and questions about what it is for a god (and in particular, the highest god, the One) to be free. With regards to human beings, he asks what it is for our actions to be in our control, or ‘up to us’. Plotinus ends up arguing for a very constrained picture of what it is for our actions to be up to us: we’re not properly in control of what we do when we’re ignorant or when we act on false beliefs. But even when we act on true beliefs, our actions aren’t properly speaking ‘up to us’ unless they are based on knowledge of what we should do.

What’s the difference between true beliefs and real knowledge?

If you have knowledge, then you not only believe something true, but also understand why it is true. If you have true belief without knowledge, then you are just lucky that you are right. Plotinus thinks that if you act on a mere belief of this kind, then you aren’t properly in control of what you do. For example, if you believe something just because you’ve accepted what someone else has told you, and you act on the basis of this belief, Plotinus thinks you are not really in control of what you do, because you are just going along with what somebody else has said. By contrast, if you understand why what you believe is true, there’s a sense in which you take ownership of your belief, and hence have a kind of control both over what you believe and over what you do as a result.

Plotinus also says that if you act on your passions (e.g. from anger or from appetite) then you are not acting freely. In such cases, there is a sense in which you are dragged about by your desires and emotions. Plotinus even says that you aren’t fully free when you act virtuously in response to circumstances you would prefer not to be in. For instance, if you go to fight in a war because you think this is the right thing to do given your circumstances, you are not fully free. In this case, you are not free because you are adapting to circumstances you would never have chosen to be in.

So, you have to choose the circumstances in which you act as well as how you react to them?

Plotinus thinks if you were fully in control, you would do just what you ideally want to do. That wouldn’t include going to war. People fight in wars because it is the best option available to them in their circumstances, not because it is what they would want to do if they had full control over their circumstances. Plotinus thinks that all ethically virtuous action is in response to such non-ideal conditions. Because of this, he ends up arguing that we are only fully free, insofar as we are engaged in pure philosophical contemplation of the realm of Platonic Forms.

The equivalent of heaven for Plotinus.

The idea seems to be that when you engage in pure contemplation, you assimilate yourself to the realm of the Platonic Forms. Ultimately, we aim to assimilate ourselves to the One itself.

But what does that mean to assimilate yourself to something? Does that mean you become part of that thing? Or you are one with it?

These are difficult questions. Plotinus’s view is that when you fully understand something, you become one with what you understand. And he also thinks that understanding one Form requires understanding all the others. So when you contemplate the Platonic Forms, you become one with all the Forms.

In fact, Plotinus has the view that there’s a sense in which you are always already one with the Platonic Forms. In your fallen bodily state, you engage in activities in the world, but your true self remains on a higher plane, always contemplating the Forms. For Plotinus, that’s what makes it possible for you to fully assimilate yourself to the higher realm and to be free, and it is also what justifies us in holding you responsible for your actions, even when you fail to be free.

So that sounds to me almost like a Buddhist idea. There’s a sense in which the self that you think is yourself is illusory. There’s a truer self which is what you really are.

The similarity is probably just a coincidence, but interestingly, we know from Porphyry that Plotinus was eager to learn about Indian and Persian philosophy. He even joined the Emperor Gordian III’s military expedition to Persia, in an attempt to do so. But the expedition was unsuccessful. The emperor was assassinated and Plotinus made his way to Rome.

The aim of the Buddhists would be to achieve no self, but that might be what you have when you’re assimilated to ‘the One’. Presumably, everything that really exists is the One. Is everything that really exists part of ‘the One’ or do all the other Forms still exist?

For Plotinus, everything is ultimately derived from, and in some way dependent on, the One. The One itself is perfectly simple. Plotinus tells a story about how the different levels of his ontological hierarchy can be derived from the One. For instance, the Forms exist because the One overflows in its abundance, as it were. This overflow from the One strives to return to the One by attempting to grasp the One intellectually. That is impossible, so the attempt fails, but in making this attempt, this overflow from the One succeeds in intellectually grasping itself. In doing so, it constitutes itself as the Platonic Forms. The Forms make themselves as like the One as possible, by unifying themselves in a kind of self-knowing activity, but they remain distinct from the One.

As I said, the other main question Plotinus addresses in Ennead VI.8 concerns the One. After discussing what it is for our actions to be ‘up to us’, he asks about the One: is the One free? Does the One have control over what it is or what it does?

“The Neoplatonists have a very demanding notion of freedom”

Plotinus raises a puzzle. Nothing can cause the One to be the way it is, because if anything caused the One to be as it is, then that other thing would be the highest thing. But if nothing causes the One to be as it is, that suggests that the One is the way it is by chance. And Plotinus says that it can’t be right to think that the One is the way it is by chance. Remember that the One is meant to be the source of all goodness. How could it explain the goodness of everything else if it were simply the way it was by chance?

An obvious solution is to say, ‘the One isn’t caused to be as it is by anything external. Instead, it causes itself to be as it is’. But Plotinus can’t say that either, because he thinks that something could only be self-causing if it were complex. A self-causing thing would have to be both cause of itself and caused by itself, so it would have to have two aspects: as cause and caused. But the One is meant to be something that has no complexity at all. So it can’t be self-causing.

In fact, Plotinus claims that the simplicity of the One raises a deeper problem. If the One is in no way complex, how can we say anything about it at all? How can we be having this conversation about the One? Plotinus wants to say that, strictly speaking, you can’t talk about or think about the One. So all the stuff we’ve just been saying about the One can’t really be right.

In the second half of Ennead VI.8, Plotinus is struggling with these problems. His response is to advocate a kind of ‘as if’ way of talking about the One. Instead of claiming that the One is self-causing, we have to say that things are ‘as if’ the One is self-causing. Strictly speaking the One is ineffable: we cannot say or think anything about it. But nevertheless, we need to be able to gesture towards some truths about the One, if we are to encourage people to strive for what is best, so we need some way of gesturing towards the ineffable. Plotinus’s struggles with this problem influenced later Christian discussions of how one could or could not talk about God.

There’s a long tradition in Islam and Christianity of God being incomprehensible in some ways to humanity. The limits of our intelligence are met when we try and think about something so different from us. So, the start of that is in Neoplatonism.

There is certainly quite a sophisticated discussion of this puzzle in Plotinus. The later Neoplatonist philosophers tend to be stricter about insisting that we cannot make positive claims about the One at all, so they reject even Plotinus’s qualified way of talking about the One.

This sounds a bit like the role of noumena for Kant, the ultimate nature of reality that we can’t access directly. Kant gets around that by thinking that you can have some kind of transcendental argument that leads to you being able to say something about the thing you can’t say anything about, and also you can have direct experience of the will. That is an indirect way of finding out about noumena, as I see it. Do you think that’s Plotinus’s influence on Kant?

I don’t know whether Kant studied Plotinus, but he would surely have studied Christian thinkers who were influenced by the Neoplatonists. Some of the German Idealists certainly read, and were influenced by, the Neoplatonists.

As somebody who hasn’t read Plotinus, I am persuaded by your enthusiastic description. It makes him sound like an incredibly clever thinker, a really imaginative logical thinker, pushing ideas as far as he can, recognizing the limitations of reason, looking for another solution. Given the premises that he had, he seems to have been something of a genius.

Yes, I think he’s a deep and imaginative thinker. He’s in some ways less easily accessible than, say, Plato and Aristotle, at least for people trained in modern analytic philosophy. Although I think that difference can be overplayed. Some bits of Plato and Aristotle are also difficult for analytic philosophers, but that doesn’t stop us studying their works. It’s not as if the works of Aristotle and Plato are all transparent, easy, and straightforward.

The second primary text that you’ve chosen is On Abstinence from Killing Animals by Porphyry (translated into English by Gillian Clark).

As I’ve said, Porphyry was one of Plotinus’s pupils. In this treatise, Porphyry argues for vegetarianism and, more generally, that we should not kill animals apart from in self-defence. There were earlier traditions of vegetarianism in Greek philosophy, but Porphyry gives us insight into a range of arguments for and against meat eating. The treatise is written as a letter to a friend, Castricius, a fellow Platonist who had reverted to eating meat. So this treatise is addressed to somebody who shares a lot of Porphyry’s presuppositions, trying to explain why he should be a vegetarian.

One argument is that it’s not good for you to eat meat—and spiritually not good for you, not just bad for your physical health. The Neoplatonists thought, quite generally, that indulging in luxury is not good for you. You should be attempting to detach yourself from bodily things, as far as is possible. By indulging your appetites you tie yourself more firmly to your body. So one argument against meat eating is that it undermines your attempt to assimilate yourself to the divine.

“One argument against meat eating is that it undermines your attempt to assimilate yourself to the divine”

A very different kind of argument responds to a Stoic view of our relations with other animals. sto held that non-human animals don’t fall within the sphere of justice, because such animals don’t have reason. On this view, we are only bound by the demands of justice when dealing with other beings that are rational. Porphyry has a number of arguments in response to this line of thought. One is to claim that the distinction between humans and other animals is much blurrier than the Stoics supposed. We can communicate with, and even train, certain animals. That suggests that such animals have at least some degree of rationality. Even those animals that don’t communicate with us often seem to be communicating with each other. We can’t assume that they don’t have reason, just because we aren’t able to understand them.

Another argument is that your behaviour towards non-human animals is likely to end up affecting how you treat other human beings. So there’s a kind of slippery slope. If you are prepared to kill and eat non-human animals, then that’s going to impact your attitude to other human beings, too.

Those arguments have parallels in contemporary debates about vegetarianism and the rights of animals and how we should treat other animals. But again, I don’t think I’ve seen Porphyry’s versions of these arguments referred to. People have arrived at those sorts of arguments independently, I suspect.

That’s probably true, though Porphyry’s treatise has been getting quite a bit more attention in recent years, mainly because there’s been a revival in studies of late ancient philosophy. For instance, Richard Sorabji has written interestingly about ancient Greek attitudes to non-human animals in his book, Animal Minds and Human Morals.

One reason why certain ancient philosophers, in particular Platonist philosophers, tend to be vegetarian, is that they follow Plato in believing in reincarnation. You might be reincarnated as a non-human animal. Perhaps these views about reincarnation also encouraged the idea that there’s more continuity between humans and other animals than some other philosophers had thought. But this is also in tension with a view many Neoplatonists had that human beings are distinctive in being rational, and that that is why human beings (unlike non-human animals) are blameworthy when they act badly.

Was this written for students as it were, or was it for a general readership?

It was written as a letter, but it isn’t a private letter. It’s quite a long and complex treatise. Given its length, it must have been intended for wider dissemination, but it presupposes quite a lot of knowledge, so I don’t think it can have been intended as a popular work for a general readership.

What’s your final book choice?

My last choice is a book by Proclus, On Providence (translated by Carlos Steel).

As I said before, Proclus was a fifth-century philosopher. We have many of his works, including substantial commentaries on Plato’s Republic, Timaeus and Parmenides. His Elements of Theology is an attempt to lay out the whole of Neoplatonic metaphysics, in an axiomatic form, modelled on Euclid’s Elements. This is well worth looking at (and there is a wonderful translation and commentary by E. R. Dodds), but it is quite hard, so I have decided instead to recommend On Providence. This is one of three short works Proclus wrote, all of which deal with questions about the problems of evil, providence and freedom.

‘Providence’ is a word that most of us recognize, but don’t really know what it means. It might be worth glossing it?

By ‘providence’, he means divine influence over the world for the good.

Is the idea that there’s a god that intervenes to help people?

Not really. Proclus has a very non-anthropomorphic idea of divinity. The highest divinity is the ultimate first principle, the One. This has the role of Plato’s Form of the Good. There were lesser types of divinity below this ultimate first principle. Divine beings do not engage in anything analogous to human action, so it is misleading to describe them as helping us. Nevertheless, they have an influence over everything that happens, and this is an influence for the good. Everything in the cosmos is in some way ordered to the good, because everything is governed by these divine principles, and ultimately everything is derived from the first principle, which is the One or the Good. If that’s so, then this raises questions as to how we can make sense of human freedom, or of human evil.

Like Porphyry’s treatise on vegetarianism, On Providence is written in the form of a letter. Proclus addresses someone called ‘Theodore the Engineer’, who had a very mechanistic view of the universe. Theodore basically seems to have thought everything in the cosmos works mechanistically, like clockwork, and ‘everything’ here includes human beings. On this view, there is no human free will, and humans cannot rightly be praised or blamed for anything they do. This is the view Proclus sets out to refute.

Proclus argues that if we are to understand what is wrong with Theodore’s view, we have to distinguish rational souls from physical bodies, and relatedly, we have to distinguish between Providence and Fate. The Stoics had regarded ‘Fate’ and ‘Providence’ as two names for the same thing. Proclus disagrees. He argues that Fate and Providence represent different kinds of causal influence. Fate is a kind of causal nexus that governs physical things. If everything were fated, then there would be no free will. We would all be pushed and pulled about mechanistically. But Proclus thinks that human souls are not physical things. They can be caused to be the way they are by Providence, without this undermining free will. So Proclus thinks there are two different kinds of causality, one appropriate to physical things and another to rational souls or intellects. Being fully determined by the former kind of causality would be in tension with being free, but being fully determined by the latter kind of causality is compatible with being free.

Another question Proclus discusses concerns divine knowledge of what will happen. If there is an all-knowing god, then that god knows what’s going to happen in the future. How, then, can we be free to act in one way or another? Proclus argues that divine knowledge of the future is compatible with human free agency: I can still count as acting freely even if what I will do is already infallibly known by some divine being.

So it’s a version of compatibilism, making free will compatible with determinism?

Yes. A kind of compatibilism. But the interesting extra dimension is that, for Proclus, if everything we did was subject to physical causes, then we wouldn’t have the right kind of control over what we do. So his version of compatibilism depends on making this distinction between different kinds of causation.

There’s a sort of dualism too. It seems that there are two sorts of things, the stuff which is subject to mechanical cause and effect relations, and then a spiritual stuff, which is subject to a different kind of causal relation.

Yes, it is a kind of dualism. The way in which it’s different from certain more familiar, modern versions of dualism is that the spiritual and the physical are not two distinct substances. For Proclus, everything that is physical ultimately depends on and comes from things that are spiritual, or immaterial. Modern philosophers worry about how these two different kinds of things could interact. That worry does not arise for the Neoplatonists, since in their view the physical stuff only exists in the first place because it is in some way derived from the non-physical higher beings.

I know you’ve devoted a lot of time and energy to thinking about Neoplatonist thought. How do you justify that to yourself? Is it like a crossword puzzle for you, or is it something that feeds back into life in other ways?

It’s not like doing a crossword puzzle; it’s more like a great imaginative adventure. Ultimately, I’m interested in questions about free will and responsibility, the nature of human reason and the limits of understanding, self-knowledge, self-determination, and so on. For me, thinking about the Neoplatonists is a way of thinking about these questions. I don’t study the Neoplatonists because I believe they have the right answers. But I do think that engaging with these rather alien thinkers can help us to better understand ourselves. This is partly because we come to understand ourselves better when we see our own assumptions against the backdrop of alternative possibilities, but also because many of the concepts we employ in philosophy today have grown out of earlier discussions in the history of philosophy, and the Neoplatonists had a crucial influence on some of these earlier discussions. We can better understand our own use of these concepts if we know their history.