There is very little in common between someone who uses a hammer to hammer in nails, and someone who uses to crash the sculls of saracins. One is a knight, another -- a carpenter: two very different life scenarios, yet they could be both classified as "hammer" type. The same with psychological functions. Two people that use Introverted Intuition for instance can have nothing in common. Introverted Intuition can be sentimentality, or imagination, or prediction, or faith. The introverted intuition of a composer would be as different from the introverted intuition of a painter as feeling from thinking. Indeed we may want to look at subtypes as separate types. Functional types is an easy way to classify people when you are dealing with a very large quantity of impirical data. In this case even eight types would be enough. However, when you are analyzing an individual, everything is not so cut and dry. The type relationships will not work maybe 50% of the time. It works in theory. But in practice, the same function may mean totally different things for different representatives of a type. There are innumerable(!) subtypes. But as students of life and society, we should distinguish a few common ones. It may be three for one type, five for another, two for another. It does not have to be even, because the landscape of life isn't even.