A 16th-century European physician would look at a person and describe their emotional state in terms of a balance of the four humors. For them, it was a useful system of taxonomy. He (usually this was the case) could talk about a person who suffered from an excess of black bile and a deficiency of green bile, and another physician would understand, generally, what sort of behavior to expect from this person. Such descriptors are merely a way of quantifying something. You can be as precise or as general as you like. You can have one hundred categories or you can have two.
Take taxonomy. Sometimes it is sufficient to describe all living things in terms of their kingdom -- you are a eukaryote, many of the things that live on you are prokaryotes. Finer subdivisions are made -- unicellular protists vs. multicellular organisms, plants vs. animals, vertebrates vs. invertebrates, and so forth. You can even winnow it down to describe an individual species, or a subpopulation within that species, which is very specific indeed.
But within that subpopulation you will still find variation. For instance, you might wish to divide the human species into 16 categories according to personality as defined by a predetermined set of behavioral traits, which you survey by answering a set of questions. This does not mean that finer gradations cannot be made, nor does it mean that there will not be individuals who do not fit easily into one class or another. (To this end, I ask you -- how thoroughly have you examined the methodology of this test? Do you really understand how it works, or do you just use it as a tool for classification? That is, are you a theorist or a technician?)
(And as for you assertion that somehow my present endeavors limit my ability to assess personality: I previously spent ten years studying and performing a theater, which is nothing if not primarily a tool for codifying human behavior and personality. I'd like to think during that time I developed some tools for both classifying and unclassifying, too.)
