Honey, I Shrunk the Philosophers

A dress that looks black and blue to one person looks white and gold to someone else. Where one person hears ‘Yanni,’ another hears ‘Laurel’. A bucket of tepid water feels hot to cold hands but cold to hot hands. Sauerkraut and black licorice taste delicious to me, disgusting to my partner. The iridescent colors of oil slicks and DVDs change depending on how you tilt your head. European philosophers in the 17th and 18th centuries were fascinated by these kinds of sensory variation: cases where something looks or feels different from different vantage points, in different circumstances, at different times, to different people, or to different kinds of perceivers.

These kinds of variation are troubling because we lack good methods for deciding whose way of seeing things is right and whose is wrong. There doesn’t seem to be any correct answer about whether the name is ‘Yanni’ or ‘Laurel,’ or whether sauerkraut and black licorice are delicious or not. The difficulty of adjudicating these disagreements suggests that color, sound, temperature and taste are not fully objective features of the world and that they exist, like beauty, only in the mind or eye of the beholder.

Still, we might hope for agreement about some things, like size and shape. Although size and shape can look different depending on where you are standing, we typically agree about where to stand to discover the true sizes and shapes of things. A mountain might look like a small hill on the horizon, but as you approach you see the mountain for what it truly is. A tower might look round in the distance, but upon closer inspection you realize that it’s square. An oar looks bent in water, straight when it’s lying on the dock. In the case of size and shape, the sensory variation seems tractable, since we assume that we can distinguish the correct way of seeing size and shape from the misleading and perspectivally distorted ways. As a result, we are much less tempted to think of size and shape as subjective.

In the Search After Truth, Nicholas Malebranche (1638-1715) challenges the assumption that there is always one correct way of seeing size. To illustrate this point, he describes a pair of thought experiments in which an object’s apparent size varies drastically depending on who is looking at it. The first imagines a miniature world:

But to better understand what we should judge concerning the extension of bodies [i.e. size] on the basis of the testimony of our senses, let us imagine that from a quantity of matter the volume of a ball God has made a miniature earth and sky, and men upon this earth having the same proportions observed in the larger world. These tiny men would see one another, the parts of their bodies, and even the little animals that might bother them, for otherwise their eyes would be useless for their preservation. It is obvious on this supposition, then, that these tiny men would have ideas of the size of objects quite different from ours, since they would regard their world, which is but a ball to us, as having infinite space, more or less as we judge the world we are in.

(Search, OC I: 87-8/LO: 29)

From the perspective of these mini people, their world looks just like ours. Their houses, palm trees, and books look to them just as our houses, palm trees, and books look to us. The variation comes in when we consider how one and the same object—say, a palm tree from our world—would look to one of these mini people and to us. This palm tree would be vast from their miniature perspective: larger than their solar system, their galaxy, many times larger than their universe, in fact. Imagine gazing up at the stars and seeing the stripes of a palm frond sweep across the sky. From our perspective, in contrast, the palm tree would be plain old palm-tree sized. That’s what Malebranche is getting at when he writes ‘these tiny men would have ideas of the sizes of objects quite different from ours’.

Malebranche’s initial thought experiment is a radical version of the 1980’s classic Honey, I Shrunk the Kids. This movie dramatizes the way ordinary household objects would look if we were a lot smaller, so that blades of grass or a bowl of cheerios seem strange. If we grew up watching this movie or others like it, such as Antz or A Bug’s Life, we will probably feel comfortable with this imaginative exercise. But Malebranche worries that his readers won’t be able to wrap their heads around it. Microscopes were a recent invention in the 17th century and the idea of a microscopic world populated by organisms invisible to the naked eye was still unfamiliar. This leads Malebranche to propose a second thought experiment, which he thinks will be easier for his readers to understand:

Or, if it is easier to conceive, suppose that God created an earth infinitely more vast than the one we inhabit, such that this other world would stand to ours as ours stood to the one we were just speaking about in the preceding supposition. In addition to this, let us suppose that God preserved among all the parts composing this other world the same proportion as among the parts composing ours. It is clear that the men of this other world would be larger than the space between our earth and the most distant stars we see; this being so, it can be seen that if they had the same ideas of the extension of bodies as we have, they would be unable to discern certain parts of their own body, while they would see certain others as having an enormous bulk. As a result, it is ridiculous to suppose that they see things as having the same size as we see them.

(Search, OC I: 88/LO: 29-30)

Malebranche imagines an enormous, more-encompassing world in which our world would be the size of a snow globe. From the perspective of the giants who inhabit this world, their world looks to them much as our world looks to us. When the giants consider an object from our world, they will see it differently than we do. Everest would be a speck of dust or lint to them, a mountain to us.

These thought experiments show that how big or small things look depends in large part on how big or small you are. Although Malebranche’s thought experiments may seem fanciful, we are all familiar with this point from the simple fact of growing up. Your elementary school, your childhood home, or even your parents might have looked big to you as a child. As an adult they look diminished. Our world shrinks, in our experience, as we grow, so slowly that we don’t notice. Perhaps this is why we can never truly go home.

Malebranche’s thought experiments present a dilemma. On the one hand, none of his perceivers—mini, normal, or giant—can really claim that their way of seeing size is right, while the others get it wrong. The mini people see size in a way that works for them. And so do we, and so do the giants. On the other hand, size isn’t wholly subjective. If I look at a full-grown palm tree from my world and see this tree as pocket-sized, then I will be mistaken. I will bump up against this mistake as soon as I try to put it in my pocket. The puzzle, then, is to explain how both sides of this dilemma can be true. How can these different perspectives be equally correct, while still allowing for some degree of objectivity in size perception?

Malebranche’s solution is that perceivers see relative size. Perceivers see a palm tree in relation to their own bodies. A palm tree from our world is intergalactically huge in relation to the mini person’s body, moderately sized compared to a typical human body, and vanishingly tiny in comparison to the giant’s body. When I look at the palm tree, I see the palm tree as roughly my height, which it is. When the giant looks at the very same palm tree, they see the tree as vastly smaller than their body, which it also is. Sight detects body-relative size.

This approach to size perception allows Malebranche to explain how the mini, normal, and giant ways of seeing size could be simultaneously correct, without making size wholly subjective—something that exists only in the eye of the beholder and where anything goes. In one sense, Malebranche abandons the idea that there is an objective or universal standard for size. There isn’t one way that size should look to all people, everywhere, and at all scales. Instead, Malebranche suggests that perceivers of different sizes should perceive size in a way that is adaptive given their bodily needs and scale. A mini person correctly perceives things in relation to his body, a giant in relation to hers. So there are standards for how big or small things should look. But the relevant standards are tied to an individual perceiver’s body. It’s not one size fits all. Our bodies are the measure.

For more discussion of these topics, check out my recent paper in the summer 2020 issue of the Journal of the American Philosophical Association, “‘Let us imagine that God has made a miniature earth and sky’: Malebranche on the Body-Relativity of Visual Size”!

Photo by Maria Stewart on Unsplash

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