To enjoy buying and drinking wine means we have to willfully succumb to certain fictions. We pretend, for instance, that we know what the juice inside the bottle will taste like. We do so based on visual clues from the words and art we see on the label, or if we previously tasted another bottle of that same wine. In reality, nothing could be further from the truth: Tasting wine is much knottier than that.

Heraclitus famously said that no man has ever stepped in the same river twice; he could just as easily have said that no one has ever tasted the same wine twice. Wine is a living thing, elusive and mysterious. It changes not only from vintage to vintage and from bottle to bottle, but even from minute to minute, according to arcane alchemy involving some of the most complex chemicals in the world interacting with untrustworthy human sense receptors.

But one of the most important aspects of how a wine tastes is, simply, everything we think we know about it. Study after study has proven what most of us already know, on some level: The taste of any given bottle of wine is determined in large part by our own subjective mood and surroundings. The price we paid, especially, is a key variable: The more a wine costs, the more we like it.

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If you think that wine labels don’t matter, that they don’t affect the way a wine tastes, think again. What you think about a wine absolutely makes a difference to how much you enjoy it. And labels play a very important role in how you think about what you’re drinking.

All wine labels tell you what’s in the bottle: what grape it’s made from, where it comes from, who made it, how old it is, that kind of thing. There are also often various forms of third-party endorsement, such as medals from various wine contests, or the logo of a well-known importer vouching for the wine’s quality.

Then there are the visual and tactile semiotics of the wine label — the large and small details which the winemaker and the label designer use to try to convey a certain impression of what to expect when you open the bottle. (And remember, what you expect plays an enormous role in what you end up tasting.)

Is the name of the wine some kind of bad pun? Cardinal Zin, say, or Goats do Roam? That’s the winemaker trying to put you at your ease, basically telling you not to be intimidated.

Is there lots of elegant script accompanying a line drawing of a grand chateau? That’s the winemaker telling you to be intimidated, conveying a long and dignified history which you’re probably barely capable of fathoming.

Is the paper for the label especially thick, or the glass for the bottle especially heavy, or the gilding on the label especially ostentatious? That’s an unsubtle signal that this is an expensive luxury product, something truly special, probably worth paying a premium for.

Most wine labels are pretty conventional, and it’s easy to see why. Imagine a bottle of wine with no label at all — just a plain bottle with no markings whatsoever. It just doesn’t feel the same. With something as hard to nail down as wine, a label gives us certainty, safety, something to hold onto. Consider this: Bottles of wine with torn or damaged labels regularly sell at a significant discount, even though that has no effect on the juice inside.

In turn, wine-label conventions have created a counter-convention. If you see a wine label that is particularly outré, if it’s very colorful or cartoonish or hand-drawn or looks like it probably belongs on an obscure craft IPA rather than on a bottle of wine, then there’s a good chance that it’s a natural wine, farmed biodynamically with wild yeasts and minimal intervention. The idea is to make the wine look a bit weird and funky, so that people are less likely to be surprised if and when it tastes that way.

The main job of a wine label, however — and even many wine professionals don’t fully understand this — is to kill that which is most alive in wine, to zero out its inherent uncertainty. The goal is to reduce any given wine to something static and repeatable. If you’ve drunk a certain wine in the past, and you then drink another bottle with the same label, it’s incredibly easy to relax into the fiction that the wine you’re drinking is the same as the wine you drank last time around.

That’s a necessary belief, on many levels. No retailer could ever sell a wine, no sommelier could ever recommend a bottle, unless they were working on the assumption that all bottles with the same label contain basically the same wine.

But of course that’s not true. Even if you pour two glasses from the same bottle, professional judges will rate them differently. The wine you taste when you’ve just opened a bottle is very different from the same wine just a few minutes later — and different still from how it tastes when you’ve moved on from your starter to your entrée, or when you’ve just heard some good news, or when someone makes a comment about a specific aspect of the wine.

The problem is that there’s no real way to analyze that kind of complexity. So while the liveliness of wine is a large part of why millions of people love it so much, the conversation about wine — both written and spoken — invariably simplifies it to the point at which the wine label effectively becomes the basic atomic unit. If two bottles have identical labels, then they, and their contents, are considered identical, interchangeable, fungible.

That white lie is the thing that allows us to talk about wine, to treasure a bottle we haven’t opened, to be able to associate certain memories with certain names. It’s a mental shorthand, without which we’d be effectively incapable of navigating the world of wine at all.

Still, it’s important to remember that the map is not the territory. And the label is not the wine.