At least a few times a year, friends and I will take part in the food classification debate. The premise is to take some food item and attempt to classify it. This can generate some funny results. For example, some may argue that by the location of cookies and filling, Oreo’s are technically sandwiches.

Sounds like good fun, right?

Well, there’s a wall of text below, so let’s try to be painfully pedantic.

A Cube-Rule Primer

Twice in the past few weeks, folks around me have brought up the Cube Rule of food classification. The basic premise is that foods can broken up into classes “purely by the location of structural starch”. Considering that a cube has six sides, foods can be classified by where the structural starch (ss) of the food would be located on the cube. Thus, there are six categories to start with:

  1. Toast: where the ss is on one side, (almost exclusively the bottom) of the food. Popular examples include pizza, nigiri sushi, and a pumpkin pie slice.
  2. Sandwich: where the ss is on two sides, (almost exclusively) the top and bottom of the food. Popular examples include quesadilla, toast, and victoria sponge cake.
  3. Taco: where the ss is on three sides. Popular examples include hot dogs, sub sandwiches where the bread is not completely cut through, and a slice of pie.
  4. Sushi: where the ss is on four sides. Popular examples include falafel wraps, pigs in a blanket, and enchiladas.
  5. Quiche: where the ss is on five sides. Popular examples include cheesecake, soup or salad in a bread bowl, falafel pita, deep-dish pizza, and key lime pie.
  6. Calzone: where the ss is on all six sides. Popular examples include burritos, corn dogs, whole pies with crust on top, as well as dumplings, and pop-tarts.

Building on these six categories, there are three more circumstances that the cube rule acknowledges:

  1. Salad: where the food has no ss. This could mean there is no starch or that the food ’s starch carries no discernable structure. Popular examples include steak, flan, creamy and smooth mashed potatoes as well as chocolate and soup. Note that in the website for the cube rule, soup is specified as being wet salad.
  2. Cake: where the ss is layered on the top and bottom as well as in one or more planes parallel to the top and bottom layers. Popular examples include lasagna, a big mac, and a stack of pancakes.
  3. Nachos: where the ss is situated within the food item. Popular examples include poutine, lucky charms, salad with croutons, fried noodles, couscous, and ramen.

Two other guiding notes are provided with the classification rules:

  1. Blocks of starch, such as muffins, are a type of toast in its raw, unsliced form.
  2. The nature of rice is interpretable in however the classifying party desires.

Why the correctness of the cube-rule matters

When I first started putting my thoughts together on the cube rule, I took this task as nothing more than a fun little thought experiment.

But then I noticed something at the top of the cube rule website: The cube rule is sited by the Maryland Courts. Clicking the image of the Maryland Courts logo on the cube rule website takes a user to the Maryland Court of Appeals ruling on Pizza Di Joey et al. Vs the Mayor and City Council of Baltimore.

The specifics of the case aren’t as important to me as the fact that the cube rule was sited by the Judge. The Judge suggests the city of Baltimore could adopt the Cube Rule for identifying foods for tax and legal purposes. Although the Judge notes that the rule’s quality can be argued:

This Rule hardly can be said to yield uniformly satisfying answers

it is meaningful that the cube rule is sited at all. Although this may be a fun piece of internet lore and source of pub arguments, the cube rule could be something used to decide the livelihood of businesses.

The cube rule is more than just fun for me at this point - it’s something worth serious consideration.

Why the cube rule is wrong

If it was not clear already, I believe the cube rule is wrong. If you stop reading here, my reasoning boils down to this: the cube rule doesn’t perform the duties of a classifier well.

What it means to classify

Classification allows for two things. First, classification allows for saying something general and unchanging about an item. In other words, a classification of an item should be final and all encompassing of the experiences of the item. Second, classification must allows for generalizing about individual classes. That is, classification must allow for describing what a class member has in common with other class members. Related and conversely, classes must be different from each other.

Given this view on classification, the cube rule does not allow for useful classification. I’ve come to this conclusion for several reasons:

1. The cube rule provides mutable classifications

Mutability describes the nature of some thing to be changeable. The purpose of classifying foods is to get at some fundamental nature of the food item. That there is something unchanging about the food that makes it a member of some class. Put another way, my desire with a classification system is to say what class a food is definitively and immutably.

The cube rule provides a definition based on the current circumstance in which the starch finds itself. This circumstance is one that can change.

For example, let’s take pumpkin pie: Crust - the starch - is on the bottom ( and kinda-sorta on the sides but not really because the crust is just bent upwards). The website for the cube rule states that if the pie is a slice, then it’s toast but if the pie is in its uncut, circular form, then the pie is a quiche. Clearly then, the classification of a food item using the cube rule is related both to its ingredients and to the current state of the food’s structure.

As another experiment: Take a burrito. In its prepared form, the burrito meets the definition for a calzone (no arguments here). Sometimes though, I don’t want to finish my burrito, so I fold the tin foil over the uneaten portion and stow it away for later. When I go to enjoy my leftovers, there is no longer 6 sides of starch holding the burrito together, only 5. Therefore, my burrito is no longer classifiable as a calzone but is instead a quiche.

My point here being that the cube rule’s classifications are mutable and dependent on the current state of the food item. Foods can change classes depending on current state of structural starch.

2. The cube rule necessitates an specific food items

See point 1 above for the mutable nature of cube rule classification. If classification is mutable, it requires that individual items are being discussed and not general types of food items. In other words, You can’t say that all pop-tarts are calzones - only that uneaten pop-tarts are.

Remember earlier, I discussed how the cube rule could be applied in real life, to decide how business is classified by governments? Because the cube rule relies on individual food items to be discussed and classified, the cube rule would not satisfactorily be usable by someone trying to classify the general foods that a business produces.

3. The cube rule does not provide insight about class membership

The cube rule is an enjoyable exercise but allows for absurd classifications of food. While yes, it is true that unconsumed wraps, burritos, corn dogs, dumplings, and pop-tarts all are completely encased in starch, what else does this classification of these foods add to our understanding of these foods? Does class membership allow the ability to discern meaningfully between classes?

Is there something specific about this classification that unifies all these items? Some of them have non-starches that are blended and not separable from their constituent parts like corn dogs or pop-tart filling but this non-separability cannot be said for wraps or burritos.

My point here is that these classifications do not allow saying something substantive about a class besides the classification criteria itself. Yes, all these items described above are encased in structural starch, but is that classification useful for these foods?

This classification doesn’t describe the taste of these foods. This classification does not describe the texture of all of these foods. This classification doesn’t describe the way in which the foods are eaten.

If the classification does not describe functional characteristics of the foods, what is the use of the classification besides a comment on the structural aesthetics of the foods?

Above, I’ve described a few of the reasons why I think the cube rule for food classification is not a good rule and why it’s important that it isn’t a good rule.

With all of the above said, I don’t believe the cube rule is worthy of being completely discarded. I believe that discussion of the structure of foods can help in identifying classes.

For example, take cube rule 8 from the cube rule website: nachos. Remember the examples: Poutine, Fried noodles, couscous, ramen, lucky charms, and salad with croutons. From my perspective there is something about the first 4-5 items that makes sense grouping them together: not only is the starch within the food item, the starch is the main point of the food item. Poutine without fries is just bacon, gravy, and cheese curds; fried noodles without noodles is stir fry; Lucky Charms without the grainy bits is just marshmallows. But a salad without croutons is still salad. So there must be something about salad that differentiates it from the other items that is not related to the structural location of starch but rather something else entirely. Yet, discussion of the structure of the food assists in this developing this intuition about the differences between salads and other foods.

I don’t have a better system for classification of food to suggest right now. Perhaps, someone is thinking about the next food classification system right now. But in the meantime, I’ll gladly discuss why I believe an Oreo is a sandwich.