This sort of variation in interpretation is one reason why word descriptions of wines are frequently disparaged, because it is often rather difficult to work out what all of this flowery language is supposed to mean (see my post on Wine writing, and wine books). In turn, this dissatisfaction is one reason why wine-quality scores are popular, because mathematics is supposed to make communication pedantically precise.
For example, in the early 1900s Jacques Futrelle created the character Professor van Dusen (also known as The Thinking Machine), who solved mysteries by the remorseless application of logic. His mantras was: "Two and two equal four, not just some of the time but all of the time".2 This emphasizes the ultimate goal of mathematics as a language, that we cannot go wrong — a mathematical proof of a proposition is as close as we can get to certainty.
However, to use of this advantage we must be rigorous, and be pedantic about our intention, as well. This is often problematic, because most people manage to forget all of the mathematics they were taught at school, within minutes of leaving that school for the last time.3 For example, you should all recognize that van Dusen is actually wrong, because the assumption that the sum uses base10 is not warranted, and in base2: 1 + 1 = 10. 4
So, wine-quality scores will only be at their best as a means of communication if they follow the logic of mathematics. Sadly, they rarely do.
Best-case scenario
The first widely applied wine-scoring system was the 20-point scale developed in the 1950s by Maynard Amerine and his colleagues at the University of California, Davis. In this scheme, each organoleptic characteristic of the wine is assigned a number of points based on its perceived quality, and these points are summed to produce the final score. The wine characteristics include: appearance, color, aroma and bouquet, total acidity, sweetness, body, flavor, bitterness, and astringency,
In theory, everyone who uses the UCDavis scale should be "speaking the same language"; and therefore any differences in wine scores should represent differences in perceived wine quality, not differences in the use of language. However, in practice, this will be true only if summing the sub-scores makes mathematical sense — if this is not so, then the sum is not a repeatable mathematical quantity.
For the sum to make any mathematical sense, each possible quality point has to mean exactly the same thing as every other possible quality point. That is, a point for color has to mean exactly the same thing as a point for astringency; if not, then adding the points has no precise mathematical meaning. Furthermore, every user has to mean exactly the same thing when they assign each quality point. It is like counting apples — we all need to agree on what an apple is, and then we need to be able to recognize each apple when we see one; if I try to add 3 apples and 3 blackberries, the sum of 6 may not make much sense.
Is this required uniformity of the points likely to be true in the case of wine-quality assessment? I doubt it, although I would love to have someone demonstrate that I am wrong. This means that, even in this situation, where the input to the quality score is pre-specified as the sum of a set of parts, the mathematics is not helping us communicate as much as we would like. And this is the best-case scenario!
Usual scenario
On the other hand, most wine commentators do not use any such scoring scheme. Their wine-quality scores are personal to themselves. That is, the best we can expect from each commentator is that their wine scores can be compared among themselves, so that we can work out which wines they liked and which ones they didn't. However, the scores cannot be compared between commentators at all.
I have shown this unfortunate situation in two main blog posts, where I directly compared the scoring systems of several professional commentators for the same wines:
No-one's scores were the same as anyone else's, irrespective of what set of points they used. So, differences between scores could mean differences in wine quality, but they could just as easily reflect differences in the interpretation of the numbers. In this case, the numbers are no better than are words as a means of communication. It is like watching someone from Scotland trying to talk with someone from Texas — they may ostensibly be using the same language (English), but they may also find that their communication is an uphill battle.
Conclusion
Obviously, we shouldn't conclude from this that points are pointless. But we might conclude that the sometimes-heard argument that numbers are more precise than words does not really apply in the case of wine-quality assessments. Even in the best-case scenario, where sets of points are added together to produce the score, might make little mathematical sense.
I believe that this is the main reason why the best-known mathematically trained wine commentator has repeatedly said that she is wary of assigning quality points to the wines that she tastes. This is Jancis Robinson, who has a degree in mathematics (and philosophy) from the University of Oxford. As far as I know, she has never put it this way, but she could do so with perfect assurance: wine assessment is no better using numbers than words, because the numbers violate many of the mathematical requirements for a precise language.
Postscript
Tom Wark has posted a very intersting response to my comments over at his Fermentation blog: A wine rating is an adjective, not a calculation. In one sense he does not disagree with my conclusion, but instead disputes the premise that numbers must be treated as calculations. My reply (as posted on his blog), is to question "why, given that the numbers are not mathematics, we are using mathematical language in our attempt to communicate. To me, this is like using English words without creating English sentences! So, if a wine rating is an adjective, then don’t use a number, because this is a very poor substitute for an adjective."
1 Unless I happen to like the sound of your voice! I have long thought that one reason the English have traditionally disliked the French and the Scots is that, for spoken English, both groups have accents that are much more melodious than any of the numerous English ones.
2 This idea goes back a long way. For example, in Johann Wigand's De Neutralibus et Mediis Libellus (1562) we find: "That twice two are four, a man may not lawfully make a doubt of it, because that manner of knowledge is grauen [graven] into mannes [man's] nature."
3 See Why do Americans stink at math?
4 We expect numbers to be in base10 because we have 10 fingers, but any base is actually possible, and to be pedantic we should always specify which one we are using. Computers, for example are binary, and thus use base2, while computer programming often uses octal, which is base8, or hexadecimal, which is base16. Given the number of devices in the modern world that have a computer processor in them, base2 is almost as common as base10 these days.
