In her excellent essay “Beauty Is Fit”, Sarah Perry redefines beauty as indicating a successful problem-solving strategy, saying it “has a unifying, definitive feature: it reflects the detection of fit between parts of a system.”

In art, I’ve noticed two basic varieties of fit: aesthetic fit, which I call chords, and abstraction fit, which I call maps. Both take advantage of “the nervous system of appreciating organisms” but in importantly different ways.

Chords are elements combined in a way that is appealing, but not because the combination describes reality. Chords exploit the many evolved sweet spots of the senses. They can be comprised of “real” things but prioritize creation of an experience over transmission of knowledge. Chords can be consonant or dissonant — the sum of their parts can elicit pleasure or irritation, or even revulsion. Chocolate and peanut butter fit better than chocolate and ketchup.

Maps describe what exists. They exploit the evolved need to understand how reality behaves. They can be aesthetically pleasing but they put the task of abstraction first. Maps “fit” when they achieve compression — when they eliminate redundancies in a pattern of real-world relationships without sacrificing essential features. Poor map fit is usually due to bad compression (irrelevant information that feels like fat on the bone) or outright misrepresentation (features that don’t appear in the abstracted territory). The Wire fits better than unedited surveillance camera footage or CSI: Miami.

Sometimes chords and maps are hard to tease apart. Fit feels like “yes, this is correct!” but doesn’t say why, so it’s easy to misinterpret a chord as a map and vice versa.

Chords are sometimes confused with maps because of their power to trigger associations. Food may taste similarly regardless of where we grow up, but the experience of eating a particular food may be more or less complex depending on accumulated personal and cultural context. Given relevant experience, food can conjure thoughts of home, status, or events in one’s life, but food by itself is generally incapable of triggering associations that aren’t already present.

For both chords and maps, fit depends on the problem being solved. In much fiction, selective distortion of known patterns draws attention to features that don’t fit. The premise “everything is the same as real life except some people are telepathic” must respect facts about reality, but only enough to solve the problem of being entertaining. This map/chord hybrid is called “suspended disbelief” and, handled properly, can be quite pleasurable.

Maps can be more or less ambitious depending on how much they attempt to compress. Technically accomplished portraits and still lifes are less ambitious than realistic portrayals of human emotions in films. In turn, emotions are less ambitious than the compression of entire political systems.

For example, films of the Person Without Lots Of Money Has To Make Difficult Choice genre are often accurate maps of a single person’s experience, and as such, encourage a particular sympathetic reaction in the viewer. Rarely, however, do these films zoom out to see the protagonist’s role in multiple nested systems, a change that can make sympathy more difficult.