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What’s a hole made of and other enigmas

Interview by Richard Marshall.


Roberto Casati is the philosophical disquieting muse of de Chirico as he thinks about holes and shadows, parts and places, the role of imagination, collaboration, language’s influence on metaphysics and the analytic/continental divide. Start thinking twice…

3:AM: What made you become a philosopher? Were you born into an atmosphere encouraging it, or did you overcome resistance?

Roberto Casati: I come from a family in the medical profession, but curiously enough I was the first in my family to get a scientific baccalaureate in high school, everyone else being a humanities person by education. My original interest in philosophy was more of the wisdom-historical type. My family felt I should have been better off as an engineer, so after some bargaining I took a minor in design. This opened up a whole new field of topics to think about. Visual perception being one of them – I was fortunate enough to sit in a hands-on class led by Gaetano Kanizsa, one of the most interesting figures of last century’s perceptual psychology ( I assume everyone has seen an illustration of Kanizsa’s triangle.). I think that when I’m looking for intuitions I still tap the huge visual stock that built up during those early years.


3:AM: You’ve thought about the peculiarities of holes. Kit Fine called them ‘troublemakers.’ You make a striking observation: ‘no identity without ontology.’ Before saying what you think holes are, what are the various options that you reject?

RC: The work on holes originated at a summer school in 1989 in which I attended a course on logic (on supervaluations) taught by Achille Varzi. At the same summer school Kit Fine introduced identity issues by presenting borderline cases of two distinct entities, such as two distinct shadows, that can occupy the same region of space. With Achille we started discussing various options, and holes provided many nice examples of entities about which we have rich and a times conflicting intuitions. These include the idea that holes do not exist, that holes are just parts of the holed-object, or that they are properties that we erroneously re-conceptualize as individuals. All theories we ended up criticizing in the book.

3:AM: So what are holes according to you?

RC: We tried to take some intuitions at face value, in particular the idea that holes exist, that you can count holes (so that they are not property-like but rather individual-like) and that you can describe their shape (they are not parts-of objects.) Our account is that holes are lesser individuals: they are quasi-objects, in the sense that they have most properties of individual objects like tables and chairs, in particular they are located and have a shape and a size, but they just lack materiality. One idea we worked at is that holes are actually made of something – they are made of space.


3:AM: In your book ‘Parts and Places’ you examine more mysteries of spatial things. What does it mean for an object to be somewhere? You offer a unified theory of spatial location don’t you? Can you say what the problem is and how you go about solving it? And this leads us on to one of the big subjects of your work, and one that links back to both holes and issues of non-material objects. Your book ‘The Shadow Club’ is subtitled ‘the greatest mystery in the universe.’ Why do you find shadows so mysterious? You connect them not just with intellectual puzzlement but also emotions too don’t you?

RC: Shadows are holes in light. So most of what you can say about shadows is just transferable from what we already knew about holes. At the same time shadows are holes in light, and this introduces an additional degree of complexity – and of interest. Light is our primary source of information, and holes in light are hugely informative, as they create an additional layer of patterns in the informational structure. This make shadows a bonanza for the visual system, which harvests them to retrieve a whole set of spatial properties of the perceived scene: we have distance-from-shadow, shape-from-shadow, illumination-from-shadows… Thinking of it, our visual world would be all the poorer, and our life in it all the more difficult, if it was not crowded with shadows.

I do not work much on the emotional side of shadows – this is at the boundary of my competences. At the same time, I’m interested in why certain properties of shadows led themselves to be exploited by the emotional system. There is recent work by William Sharpe on that that is quite fascinating.


There are many puzzles of shadows, but these are mostly limit cases that philosophers use for testing definitions of light and shadow. At the same time there are many wonderful examples of scientific discoveries that have been made thanks to shadows, and that could only have been made thanks to them. My favorite thinker is Aristarchus of Samos, who figured out the relative distances and sizes of Sun and Moon by measuring the angle dividing them in the sky when the Moon is halved. He came up with a result that is quite removed from the actual measurements, but he was able to show that Sun is much, much bigger than the Moon, in spite of their apparent sizes. An astounding discovery, for the time.

3:AM: In your book ‘Shadows: Unlocking Their Secrets’ you set out to understand for your own satisfaction how best to think about shadows. So what do you say a shadow is? You imagine a world without shadows to explain what they are for don’t you? So would we be blind without them?

RC: As I said, a shadow is a hole in light. This is the simplest way to characterize it. You may think of it as of an absence, but this requires you to have a theory of absences, of things that are not there, and I would prefer a simpler theory. As soon as there is light and there are objects in light, there are shadows, so it is difficult to have a shadowless world. However we can come close to a model of it. Too much light form extended light sources has the effect of creating so many shadows that they cancel out and become invisible. When you walk in a large department store you discover that there are very weak, almost nonexistent shadows. At an exhibit at DAM in Frankfurt many years back we created a shadowless room, with opaque perspex floor, ceiling and walls, backlighted with diffuse neon light, and when you walked in it felt as if you were floating in mid-air, as if there were no shadows to anchor you to the floor. Spooky.

3:AM: An interesting thing you do in that book is discuss different species of shadow – you have shadows that are created by technologies, you have ancient shadows that have always been with us and modern shadows ‘colonizing the empire of the night’ , you have New York shadows and Tokyo shadows and so on, all with important narratives attached that you then develop to deepen our understanding. Can you say something about all these various shadows?

RC: Well it’s a long story – or series of stories – but my favorite is the realization that until we had electric lightbulbs all shadows were moving shadows: both those produced by the Sun, and those produced by fireplaces and candle flames. Electricity created stable sources of light. All of a sudden our visual landscape was populated, and still is, by still shadows. I would like to call this a sort of shadow domestication. Of course the vast majority of shadows are moving shadows. Domesticated shadows are a signature of the contemporary way of living, though. Maybe there is something to be said here about the desire to be in control of each aspect of what we see.

3:AM: You were part of the homage to Hans Christian Anderson’s 1846 uncanny tale ‘The Shadow’, which included reflections on the story by artists such as Boltanski, de Chirico and others. Did you find that thinking about this story helped clarify your thoughts further about the nature of shadows and their perplexities?

RC: Here we enter the realm of imagination. I value stories and narratives (and I think they are an important part of the fabric of our life) also because they tell us something about our imaginative resources. Andersen’s story is a sort of revenge of the shadow. It has been always considered as an ancillary entity. Now it takes the upper hand. Fine. But we can only understand the story and appreciate it because we do consider shadows as ancillary entities, that is things that would not exist had their shadow-casters, and light, not existed. Shadows can have the upper hand only in a tale. In real life, they are lesser entities, forever.

3:AM: You collaborate with Achille Varzi a great deal. Do you find working with another thinker helps you philosophise better than when solitary?

RC: This is an important question and I welcome it as it also allows me to say how fortunate I have been and am in having had the opportunity to work with Achille all these years. There is something with such long-term collaborations that concerns the ethics of writing. One writes more creatively, as one knows that the other is there to double-check. At the same time, one wants to make sure that one is not wasting the other’s time and energy, thus one prunes, pays attention to dead ends. It’s exhilarating.

3:AM: And as a bilingual thinker, do you think that metaphysics is changed by the language you’re using. So for instance, is an Italian shadow different from a Danish one? I’m thinking that perhaps de Chirico’s shadows do seem Italian. And there’s a serious point maybe, that our ideas, even metaphysics, might have cultural biases? Is this something that perhaps the xphi people ought to be investigating, or do you think there are no important relevant differences derived from different languages and cultures?

RC: All I know about the issue of how language influences ways of conceiving the world points out to the fact that there are language-dependent differences, and many of them, but that these differences are small, of not much importance. Large cultural differences depend on many other factors: education, tradition, opportunities. It has to be shown that there are clear metaphysical differences here, in the sense of radically different ways of conceiving the world at a level that is immediately operant for our action. The landscape I suppose is most likely is that we all have a common core metaphysics, that is mostly a biological endowment, and that science provides the only viable alternate metaphysics. I am aware that these ideas may be controversial.


3:AM: Your book ‘Insurmountable Simplicities’ is both playful and serious, and shows your interest in telling stories that contain puzzles and paradoxes. Many philosophical papers are pretty dry and tough going, but one thing you seem to want to do throughout is make your ideas entertaining. What were you trying to do in this book and why was it important to tell the puzzles as stories? Is there something about the way a puzzle is presented that contains important elements of the puzzle that are lost if dried out, or is it more a matter of your intellectual nature to entertain? Or is it because you are working in a non-English speaking University setting where the formal constraints aren’t the same?

RC: This again is the result of the long collaboration with Achille Varzi, we wrote (and still write) these short stories for Italian newspapers, and it was very nice to see that they were translated in ten languages… so many readers wrote back to us with ideas and comments. I think the main inspiration is actually a kind of Carrollian nonsense, sometimes with Borgesian dark views. The main idea is simple. People who do scientific popularization usually tend to start out with a very complex issue and try to make it simple for their intended readers. We do the exact opposite: we start out with very simple things and try to show that there is a beautiful, hidden complexity behind even the simplest of simplicities. The hope is to invite our readers to think twice about many issues. This is what philosophers mostly do.

3:AM: Can you give an example?

RC: Why do mirrors invert left and right but not up and down?

3:AM: Your approach to philosophy is full of imagination. How important is imagination to you as a philosopher ? Do you find engaging with artists and imaginative writers as well as philosophers helps you grapple with the metaphysical issues you discuss? If so, can you say who your favourites are?

RC: I am not very good at name dropping, but let me name Borges. Concision. Sharpness. Making things visible. Images you cannot easily forget and that keep working in the back of your mind. Ideas made tangible. But I also admire the great builders, Thomas Mann, projects that take one’s lifetime.

3:AM: You’re based in Paris but are well known in Anglo/American philosophical circles. So what do you think about the so-called analytic/continental philosophy divide? Is it bogus?

RC: I studied phenomenology and history of philosophy. It’s a very continental background. I learned many techniques from many different philosophers. Philosophy is an art, not a science, and one is always trying to perfect one’s art. I think there is a divide, but it is more a matter of academic power. A bit paralyzing.

3:AM: And finally, for the budding metaphysicians here at 3:AM, are there 5 books (other than your own) that you could recommend to help us go deeper into your weird and wonderful world?

RC: David Lewis, On the Plurality of Worlds. It’s like entering a vast cathedral, a masterful construction.
van Inwagen, Material Beings. He defends the thesis that only living beings and mereological atoms (whichever elemental part your theory of the world has) exist. A powerful thought, I am not sure I adhere to it, but I like seeing the world in this light.
Jenann Ismael, The Situated Self. Deep thoughts about subjectivity.
Peter Strawson, Individuals. Took the art of thought experiments to its highest peaks.
Edmund Husserl, Ideas for a Phenomenology, the first volume. A first-person exploration of the complexity of our relationship with the world.

Richard Marshall is still biding his time.

Buy his book here to keep him biding!

First published in 3:AM Magazine: Saturday, May 16th, 2015.