It just makes my kettle boil
Recently I posted an observation to an online group and asked for comments. The observation was that, in Taiwan, nearly everyone I encounter (growers, producers, vendors and tea houses) brews oolong tea with boiling water.  The comments were not long in coming, they were many and, apart from one that dismissed the observation as incorrect (on what basis is entirely unclear,) they mostly, as I had hoped, turned on the question of what the proper water temperature for a quality brew ought to be. A few suggested that there was an ideal temperature to bring out the quality in an oolong (generally boiling, but sometimes 195°F or 90°C) but a many others maintained that it was all a matter of personal preference. And this has led me to wonder: is assessment of a tea’s quality simply, as so many claim, a matter of personal preference? Or, in other words, is quality assessment of tea an objective or subjective enterprise? And this presupposes the prior question: is taste objective or subjective? If taste is subjective it is indistinguishable from preference but if it is objective could there be “correct” and “incorrect” assessments of quality? 
What’s the objective of a transitive verb anyway?
Taste is a slippery devil of a word for it is used in so many different ways. It can be a transitive verb (e.g. “I taste tea,”) an intransitive verb (e.g. “The tea tastes bitter,”) or a noun (e.g. “The taste of tea.”) Clearly, as a noun it sometimes is used in a manifestly subjective way (e.g. “My taste is for tea not coffee.”) However, I use “taste” in the following technical way: the sensation perceived when things are brought into contact with the tongue (and olfactory receptors.) And, to avoid confusion, I will refer to this as “flavor.”
Flavor is what we perceive when we take tea (or wine, or beer, or milk etc.) into our mouths. Flavor is constructed in the brain once the receptors in the tongue and olfactory areas become activated. The chemicals that excite these receptors reside in the tea and, insofar as you and I drink the same brew, we are exposed to the same set of chemicals in the same degree. The question now is, are these perceptions subjective or objective?
All things being equal
Many claim that this is precisely where subjectivity comes to dominate the discussion; our perceptions of taste and smell are subjective representations of what is in the cup. But wait. Why is that the case? Why are the faculties of smell and taste subjective when most will admit that those of sight, hearing and touch are not? When we see red, we agree (save perhaps the color blind) that we are seeing a color that is red (even though color, like flavor, is created in the brain.) We do not decide the color is red because we have a preference for red. The color is what it is independent of our taste for it. Similarly when we touch a surface we determine whether it is hard or soft; hot or cold. An object is not hard because we prefer hard objects, it is hard because it has the property of hardness and it is so despite any preference we may have for soft objects. The properties of objects reside in the objects, not in the minds of the subjects.
And just so with the faculties of smell and taste: our perceptions are objective representations of the flavor components of our tea. The problem is, we have a much more poorly developed vocabulary when it comes to talking about flavor than when talking about color or texture. “This flag is red and white” conveys a relatively clear image of the nature of the flag. “This tea has a long finish”, however, does not convey the property of the tea with nearly the same precision. In short, we have trouble articulating our perceptions of flavor. And due to this difficulty with articulation and the fact that vocabulary is not consistent, perceptions of flavor are often wrongly assumed to be subjective.
Learning the language
But how are the limitations of language to be overcome when discussing flavor? The answer is found in experience. The more experience one has at tasting, the clearer, and more accurate the identification of flavors become. It’s like the answer to that old joke “How do I get to Carnegie Hall.” Practice, practice, practice. With practice, and as one becomes better at identifying the various flavors in tea, one also finds that there is increasing agreement with others as to what constitutes good tea. And this brings us directly to the issue of assessing quality.
The next obstacle to scale is: “what does quality mean?” Although we may be able to determine the flavor of a given tea objectively, how do we decide whether this flavor is better or worse than other flavors; what standards are used? Here I introduce the observation that all standards of quality are culturally rooted and are culturally relative. That is, to be meaningful, every evaluation must be grounded in a cultural context. In this manner, it makes sense to say Bach is a better composer for organ than Bruckner, even if one prefers Bruckner (a wild stretch for sure, but possible I suppose.) But it makes no sense to say that Western classical music is better than Chinese classical music even if we do have a preference for one over the other for the two are products of entirely different cultural contexts. Further, the fact that culture is a social construct does not confer license to claim that quality is a subjective thing. For standards of quality to be subjective, culture would need to be an individual construct as opposed to collective one; and it is not. .
We also can see now that although quality and preference may influence one another, essentially they are independent concepts. They are manifestly different things. As such preference, which is a subjective stance toward a product, in this case tea, cannot serve to make quality evaluations of tea. We cannot contend that the quality of a tea is in the eye of the beholder. We like what we like but that fact doesn’t make what we like good.
Fire burn, and cauldron bubble…
Coming full circle then, is there a correct temperature for brewing tea? I firmly believe that there is and that it can be known objectively, given a cultural context. But I am also well aware that I do not yet know what that temperature is. It will take far more brews and much more tea before I’ll feel confident to opine on that. In the meantime, can someone tell me how I get to Carnegie Hall?
That’s my take. What do you think?
 I also checked with producer friends in Fujian and Guangdong, China and they confirmed that there they too use boiling water.
 The subsequent argument assumes, of course, acceptance of the ontological position that there is a reality that is potentially knowable. Otherwise, the question is meaningless.
 See Gordon M Shepherd, Neurogastronomy: How the Brain Creates Flavor and Why It Matters (New York, Columbia University Press, 2012) and Gordon M. Shepherd, Neuroenology: How the Brain Creates the Taste of Wine (New York, Columbia University Press, 2017)
 For a discussion of this chemical makeup, see inter alia Tony Gebely Tea: A User’s Guide (Eggs and Toast Media, 2016) ch. 3
 I am well aware of the fact that individuals can have different sensitivities to the elements in tea or any other flavorful beverage. For a popular discussion see Tim Hanni, Why You Like the Wines You Like: Changing the way the world thinks about wine (New Wine Fundamentals, 2013.) Clearly Hanni and I do not agree on the objective/subjective issue.
 One online commenter used the following example: Imagine on the one hand a Big Mac and on the other a burger made with the finest ground beef, the very best bread and the most wonderful condiments. The second burger is clearly of higher quality even though many will prefer the Big Mac.
 For further reading see Barry C. Smith (ed.) Questions of Taste: The Philosophy of Wine (New York, Oxford University Press, 2007.) esp ch. 3 and ch. 5. and Michael Langford, “Are ‘Matters of Taste’ Matters of Taste? Philosophy Now no. 91, 2012 downloaded from https://philosophynow.org/issues/91 on 11/17/2017.